Seriously I love that you don't make your videos short! Please never change that. It's one of my many favorite things about your channel, the other thing I love about your channel is how much depth and attention to details you put in and you're extremely skilled at working on small engines. Your content is pure gold. Thank you for your time and pubic service to your viewers don't ever change how you make your videos ☺️
That was absolutely worth 2:15 of my time. I have a similar unit that has been under the bench taunting me. After the comprehensive video you put together, even though the machine is not 100%, I gained enough knowledge to give mine another shot. I appreciate that you took the time to show almost everything. You presented fuel, spark, timing and compression and gave each one it’s due. No one can do that in 59 minutes. Your length of video meant you could show all the complexity, and you share your process and you thinking. That is where your content has more value than most. Thank you for this video. It gives me confidence that I can try to take on a similar challenge. You have helped me a lot in the past and you continue to do so here. 6 Stars, on the 5 Star scale.
I was a mechanic for years and eventually owned a small engine shop when this engine was new. My shop was a master service dealership. I have 2 comments. First these flat head Tecumseh engines never were known to be smooth runner's. . 2nd your not considering a sticky governor. Start with checking the governor rods. For abnormal bends , and spring condition, some models in the series also had a secondary spring. To help stableize movement of the governor rod. It seems you covered all the other likely conditions well.
The governor problem would also explain the hunting at low engine speeds.Sticking flyweights could cause erratic running but I don't know about a high speed misfire.
Those things shook like Hunter Biden when he runs out of crack. Poorly balanced in my experience. That being said i don't think some had carb's matched properly. many used that offset flywheel key that could roll over but not shear and throw the timing off.
You're not alone. I "had" an 8 hp techumsa with exactly the same issue. It was on my log splitter I owned for 20 years. Because it would "run" crummy I just let-err-rip spit & sputter while I split wood. Every year or two I'd try fixing it. I did everything you did 10-times over 20 years. My carb was NLA & the closest carb I could get was for a generator. That didn't fit or work well at all. I bought every carb part available for my engine. What I ended up doing that fixed the hard starting & running ruff was....the little brass screw in jet on the top side of the carb ..... I used a finger drill & made the through hole (not the tiny side hole) larger one drill size at a time. That finally fixed it - Yahoo & sold the log splitter. I ever see another 8 hp techumsa I'm not fixing it - whatever it takes to replace it would be a shortcut. Grrrrrr8 video 👍
that would make sense as he mentioned he has to run at half choke through most of his video meaning he has to cut down on the air supply. Could mean he isn't getting enough fuel? hmmmm
I have that log splitter. Leave it parked in the barn for 6 years with fuel in the tank and pull it out leave it all winter covered with snow. Put fresh fuel in it in the spring. Hit the primer 3 times and start it. Seems to have been what mine wanted. Runs better now than when it was new.
James, I had a Coleman generator like this and it ran the same way from new. It ran fine under load but stumbled occasionally when not under load. I never got it figured-out. I appreciate your efforts and don't mind the length of this project, this is the second time I've watched it and have learned more this time around! Keep up the good work.
I know it's not the same application, but when I used to maintain a fleet of pushmowers and other motorized small engine equipment, Tecumseh always proved to be problematic for weird things like this. They were always the more tempermental units to get running and even then, they would never act really *right* when compared to B&S, Champion, and other small engines of the same form factor. I'll be watching to find out what you find out in your investigation, but that's definitely a head scratcher. From what I can tell,. you've gone above and beyond, this thing should be running like a top by now.
Another great video James ,2 tricks I use. Valve lapping suction cups are prone to not sticking very well, I now use a 3/4" dowel and stick it on with hot melt glue , works great. The other trick is when grinding the valve stem use a vernier caliper to measure valve length before grinding. Saves putting valve in and out of the block to measure the clearance. You get top marks for persistance.
When doing valves, I also use double sided foam tape, but instead of using the valve tools as shown, I use a piece of dowel wood. It works great. I never have issue now doing valves. I get them done easy as tying my shoes. The dowel never slips off till I remove it from the two sided tape and I can apply far more pressure while spinning the valves and not have them slip. I threw my valve tools away.
I think you may have a valve floating issue. Weak valve springs will do that. It would explain your higher leak down at lower pressure as well. While you did lap the valves in, your exhaust valve may be ever so slightly warped or bent as well. I'd try some valve springs.
Jim, During the 1980s, Kohler had a reoccurring problem with valves or valve guides. Similar symptoms; but, with additional occasional caveat! The exhaust valve would stick in the open position, until the engine cooled. The engine would suddenly die, and have no compression for several minutes. Eventually there would be a LOUD snap, and could then be restarted with ease. Thus, As did MarkholtropXXXX (9 months ago), I suspect a bent or warping exhaust valve. Once, we cured the problem in an Allis Chalmers Garden Tractor, by cleaning/reaming the valve guide. That unit had replaceable guides, but we lacked ready access.
I can't believe I watched all 2:14 of this! That's a testament to the quality of your content, your vast knowledge and your determination to get things done right. Your video definitely did help me. I now know to avoid alllll things powered by a Tecumseh! Ha! Some of your other videos have definitely helped me rehab a Briggs carburetor. Thanks a bunch and keep them coming.
James, have you considered tired/week value springs. The compression will test good, but week springs will not follow the cam accurately at speed, causing the intermentent misfire you're experiencing. Take them out and measure their height. And while they are out, clean the carbon and lap. Good luck. Really enjoy your videos. They are a part of my weekly must-see video list on RUclips.
I have had some similar issues before, I always go to the coil where it mounts. I remove it and clean the mounts on the block and clean where it mounts on the coil, then I use a little silicone grease before I regap the coil. It fixes the problem about 50% of the time. I hope this helps you your videos are very helpful especially on the generator side.
To prevent the tank from getting hot due to heat shield being to close place a spacer bar to raise tank up higher above the mounting bolts with spacer material
Compression ring with low tension, or weak valvespring(s), those are my guesses. Both would show better performance under load for this small engine application. Anxious to see the follow up on this one!
Hi James, to get burning gases out of the exhaust can only be a few things. Bad ignition timing I.e too late, sticking exhaust valve. Excessive un atomized or large particle fuel in the combustion chamber. An interesting experiment would be to run it on LPG or NG as the fuel is already in a gas form. This would eliminate poor carburation. Fuel injection would have a similar effect but hard to do on a budget. Some newer B&S engines have fuel injection now. We deal with 100’s of small engines at work but mostly Honda and Lifan Some Kolhler and Kubota and B&S. Interesting issue I would love to get the scope on to try and see what is really going on. You could try a video of the valve operation and then view the video in slow motion to see if there are any anomalies.
I bought a Troy Built tiller with an 8 HP Tecumseh back in the 90's. I still use it and it runs about the same as the one in this video. I gave up years ago on making it run smooth. My suggestion is to move the engine to your garden tiller. 😄
An easy way to check for vacuum leaks, or to check the fuel mixture is with a propane torch. By turning on the torch without lighting it you can introduce the propane gas into the carburetor and it will change the mixture without actually adjusting the carburetor. You can run the motor at the problematic RPM and see what changing the mixture does. This helps isolate a fuel mixture problem. By using a torch with a rubber hose attached, you can look for vacuum leaks. This eliminates spraying flammable liquids in areas where it would cause trouble. It looks like when it is backfiring flames are coming out of the muffler. My guess is the exhaust valve is sticking. If it was rings you would see excessive blow by out the crankcase breather. I didn’t see what condition the spark plug was in, but I would make sure it is the proper plug. I would replace it. I have seen spark plugs do strange things.
After i just found this video and watched it,i can see what my grandfather said was essentially true,he worked at GM for 40 years and knew his way around engines and such,he owned numerous Tecumseh powered yard equipment tools over the years,and what he said was "they (the Tecumseh engines) like to be put to work" and now i realize what he meant,also fantastic videos,keep it up John!
I have a 13hp Tecumseh on my lawn tractor. It uses the same type ignition coil. I used a timing light to check timing, they run it at 30° before top dead center. Some engines miss under light throttle with this much timing, I suggest trying an offset flywheel key if you find out your ignition timing is as mine at 30°. You can use a battery powered timing light to check this and mark the screen behind the starter with a chalk line at top dead center. My Briggs & Stratton generator only runs the timing at 0° top dead center.
That's a lot off turd-polishing for very little return! The best part about things that are hard to troubleshoot, is when you do finally figure it out and get it going.
I don’t know the first thing about small engines except how to use them. Your methodical approach and excellent narration kept me captivated all the way through. I hope you sorted the problem for your own sanity.
Hi, Jim…as you know, my field of expertise was electronics and not gasoline engines. When you made the initial test for spark I observed a really strong spark appearing on your tester. This got me thinking of possible leakage from the secondary of the coil to ground intermittently, or even from the spark plug wire itself. I used to see this happen on the secondary side of flyback transformers in older televisions that I used to repair which provided the high voltage to the CRT. Sometimes, the insulation on the second anode lead would fail and cause intermittent arcing to ground. They made a substance called Glyptol in a spray can that could be applied to the entire transformer and second anode to restore the dielectric properties of the high voltage system. It sure looked like that could be your issue until, at the end of the video, you showed where you actually replaced the coil, which pretty much blows my theory to bits. When you’ve gone through everything as thoroughly as you did and eliminated just about every possibility, you might consider a manufacturing flaw in that specific unit, one that is so small that it’s impossible to detect yet significant enough to cause the misfiring. Good try, pal. At least now I know you’re human! 😂 You’re still the best I’ve ever seen, very helpful, and most entertaining.
Your scenario was plausible indeed, until the coil replacement. If one could start the engine with the cover off and observe, perhaps we would learn something.
It could be sparking at the shutdown tang because that still has relatively high voltage pulses on it and is out exposed in the elements. It was even painted over which could be trapping dirt or moisture.
Even though you haven't solved the problem yet, this was an awesome video. I ALWAYS learn from your videos and it was absolutely worth 2:15. Great job! I hope someone comes up with an answer for this.
A great video. One suggestion is when watching for spark using light, record the spark light at high speed and watch back. At 400 frames per second you spot the missing spark.
don't worry about the money you throw at it , look at it like you paying for a education, its an education we learn..if you dont sell them you could always rent them out..great job as usual.
One thing you didn't do for most of the testing is have the air cleaner on. The air cleaner creates enough drag to affect the mixture, possibly making it too rich. You may try retuning the carb with the air filter installed, because it can change how the engine runs significantly.
Your probably right, especially with Tecumseh engines. There's a reason Tecumseh went out of business, those Chinese Honda knockoffs are assembled with far more quality.
@@brianallen9810 they didn't go out of business. They were acquired by an investment firm, and still manufacturing parts, and have a number of engines in stock. Better check Project Farm from last week on YT before you think they are better than Tecumseh. One they tested used almost half of the engine oil on a 24 hour test. They also produce more carbon monoxide than the Honda engine in the same test. The predator engine was a little bit better, but not better than the Honda engine.
@@brianallen9810 I'd have to agree on Tecumseh engines, I've never personally seen one that ran correct. My dad has this exact generator and it has never ran smooth. There was a old guy in my town that had a old rear engine John Deere mower with a Tecumseh engine and he constantly fought it for years. One day he pulled up to his house and idled it down and it threw the rod out of the block. I went to our local scrap yard and got a 8 HP Briggs and stratton and put on it. He said he just didn't know what to do with all of his time since he could just go and mow and not have to adjust the carburetor on the Tecumseh. It was still running when he passed away years later.
@@littledave601 yeah Tecumseh motors are good for either pouring oil like a siv wanting to run pretty much wide open no matter how you try to tune them or they will randomly chuck the rod out the side without any warning what so ever every one I have delt with has been like that so when get something and it has one of those on it the first thing I do is pull it and send it to the scrap yard and replace it with a good old briggs
That's a good possibility, on motorcycles it happens more than people would like to admit. Same on some GM vehicles with the MAF sensor built into the air filter housing. No filter, bunch of weird A/F related codes.
Any time you remove the head on a Tecumseh engine it is always a good idea to take an indicator and check the timing as just a change of .001 thousandth of an inch on the points can make a change in the timing. I owned and operated a shop for several years and was a certified repair and warranty center and found this to be a common problem.
I was thinking what about the points and condenser when he removed flywheel to check the key. Tearing that far down, I always checked to see condition of the points if they have a burn spot on it. Plus, I might look old with a long white beard on outside but the kid in me loves to charge up the condenser from the motors when I put new ones in. Then sit it on the table and wait. When you hear a yell you caught one. They always just need to pick it up and look at it to see what it is. Touch wire and housing at same time with bare hands and win the prize. I use to set out about 10 to 20 per week back in the 1980s. Ah the good old days. An I know alot of you reading this did the same thing. Great minds think alike. Just like grabbing a electric fence a only hold it for half a second an say nope it's not on. Then someone else always has to check it. Bigger yell. Hahaha. We had so much fun but nobody got hurt, we did get some good deep scars back then but most have faded since that time. Great video buddy. Stay safe, wear rubber gloves.
@@terrydouglas2777 Hi, when he had the flywheel off, there are no points or condenser. Tecumseh is using the B&S points eliminator coil. It has a trigger coil and a couple of npn transistors to start the electron flow and then interrupt it. So, no points on this setup.
@@baratono lol I know, wtf. Also .001 on the points would not make a difference in running anyway. It's not rocket science. It's a old school engine, they aren't too picky.
Working on a hm100 on a 5000 watt devilbiss gen, same problem exhaust valve no clearance, did valve job new head gasket, then carb same issue exactly misses at no load, but under load good. Compression 60+, will check coil and wire but beginning to think about weak valve springs or low oil sensor problems. Thanks for the good work.
The big clue here is it got worse with a new plug A stronger spark could produce a higher pressure on the power stroke because of better fuel combustion which could aggravate a problem with the valves having a weak spring and bouncing when closing I have read all the comments and concluded valve spring pressure is the most probable cause according to popular opinion I’ve never seen a new plug make things worse in any engine! That’s very unusual! ( just saying) 😀
Hey James, love your videos! I haven’t read through all the comments, & I know this video posted 7 months ago. Perhaps you’ve already found the answer. Based on 25 years experience, I think the intake guide clearance is excessive, causing the cylinder to pull air out of the crankcase. Especially when the engine has the most vacuum ( idle & no/light load at rated rpm. This also explains the hard/erratic starting. Went through the exact same thing with an HM80. Ran great under load, couldn’t make it idle properly, did everything as did you. Intake to guide clearance. Tecumseh makes 1/32” oversized stem valves.🇺🇸😊
Since you checked almost everything on the engine side, please check the generator side. If there is an intermittent short within the generator, it will introduce a brief large load on the engine. At small speeds this could be impacting the engine. Connect an oscilloscope to the outlets and check if the wave is stable.
May want to check the cam, if the cam is a bit "wobbly" it will cause these intermittent and sometimes unreproducible issues. Though it mainly affects Briggs engines from the late 2000s where the cam shaft comes loose from the gear, but there may be a burr or something like that on the cam lobe or a sticking lifter/tappet.
You really did battle this one, it so happens I learned small engine tuning on Tecumseh and they are very forgiving about carburetor settings, I have found a new spark plug helps even if the engine still runs on the old one, nice job James
Real great effort on your part here James. The length of time a video lasts is not an issue. In fact with a shorter one I'm wishing they were longer. I thank you for all your content however it comes to us.
Let me reiterate: it works well under load and that's when you need it working the most. Perhaps it is a tolerance issue in the manufacture of this engine, or there is another worn part somewhere in that old engine. Thanks for the great videos. :-)
what you can try is cleaning the mounting bosses for the coil and the two contact surfaces for the coil to the Block, you may have high series resistance between the coil body & the engine which might cause inconsistence spark especially at high RPM's. I would also wire brush the circumference of the flywheel to get ride of any rust which can be affecting the coils response. Also Tecumseh engine are notorious for bent valves so you can test it by placing them in a drill and spinning to see any irregularities, an intake valve leak would sure give you that issue too but it may not show up on a leak down test but more so when the valve lifts & rotates under normal operation..
Good idea with the 2x tape👍🏻 I don’t think I’ve ever not heard them old Tecumseh engines not pop and miss no matter what they were on. They hard to kill if maintained.
I have this same engine and after a few years, it exhibits the same exact behavior as yours. Mine is used to power a chipper shredder. I followed the same exact path you did in the video several times over the years but was never able to get rid of the misfires either. It’s the only engine (I have probably 15 or so engines across all the brands) I was unable to bring back to perfect. Finally, I set it aside and swore to myself I would not waste any more time with it, lol. And, I’ve never bought another device with a Tecumseh engine on it either. Crazy engine for sure. It will be interesting to see what you find if you open up the lower engine.
I got a free Craftsman mower with an older like 13 horse Briggs flat head. Originally i messed with the carb, nice and clean, it started PERFECTLY, ran ok but had like pops. Carb adjustments did nothing, kind of leading me to beleive carb. Also was blowing a good bit of air back through the carb. Thought it was weird, already had a new plug just because its cheap and it looked original on a 15 year old mower. Checked and the intake valve was not sealing and leaking compression, zero lash either. Got a gasket ect, lapped the valves, adjusted the lash to spec, everything should be good, yes? Well now when i adjust the carb it actually does something, still pops, it will go and run, just it doesn't sound as nice as it should, being everything is so nice and perfect. Annoying spending the time, not because it doesn't work, but because you want it perfect and it didn't really help. Not gonna throw it by any means, but its something else.
@@baileyhatfield4273 I've got one like that that the governor is very sluggish on. An 85 model 4 horse flathead with an 'all climate' carb on a Snapper 21. Didn't make many and info is less. I got a real Briggs book for all flatheads from 86 on I think but hardly anything on that engine but even less on the carb. I think i have an angle on it but will have to wait to see. Never had a Briggs to run sorry. Tecumseh? OH yeah. IF the mower had a hood scoop to pull fresh cool air in through slots in the hood to the motor intake screen and it's gone, rig one back up again. The hot air gets trapped under the hood without the foam between the hood underside and engine and it gets way too hot. I also run DELO 15/40 Diesel formula lube oil in all mine and my truck. Thicker oil lubes better and cools better.
2 hrs and 15 minutes of my life I'll never get back. Thank you, Sir, Mr. Government Engineer. Try starting with the least path of resistance. Definitely an hr government employee " Engineer.".
Nice job James! You are bringing all of us together with thinking caps on. Several things come to mind because the engine does seem to run better cold. First, fuel boiling in the carb bowl (winter gasoline can and will make this worse). Second, the exhaust valve sticking or compression release malfunctioning. Third, pre-ignition reducing the spark plug heat range. If I know you from all your videos, you don't give up unless there is an obvious flaw. I do recall more than one person installing a 8HP Tecumseh from a junk snowblower (the engines all ran great in the winter) on a log splitter which all ran like crap on the log splitter. (seem to run lean and back-fire when hot)
Hi james.great video as always, I’m actually leaning towards the compression release tap on the camshaft, in some cases when the exhaust valve clearance is too tight that can cause the tap on the camshaft to bend and consequently causing afterfire from the exhaust. Hopefully it will be easier then that and Good luck 🍀
Strange glitch at low pressure on your leakdown test. Assuming your gauge valves are not the cause I'd suspect a broken ring or ring land damage on the top side of the compression ring. I had a rototiller with the 10 hp Tecumseh and which ran similar to yours. The plug in leads for the coil were shorting intermittently to the head when up to operating temp resulting in stalling miss. Thx for the great videos James !
James, I usually watch your channel on my television, but that prevents me from commenting so I'm using my laptop. Just wanted to thank you for putting so much time and effort into your videos. I typically do my own small engine work, but I have learned so much from watching your videos. I can't thank you enough. I have even upgraded a few of my tools after watching. Thank you again for such detailed and complete videos showing diagnosis and repair!
I admire your persistence - It's heart-warming. I try to never let the value of my time exceed half the yard sale value of a project. "It's a Tecumseh - It's part of the charm" "It may sound like shit - But it starts every time and will power things up" "You'll get used to it" :)
Always enjoy your diagnosis and progress on repair of small engines. Over the years, I have worked in mine and my neighbors. Managed to keep them going. Your videos have sure helped. Very good tips. Thanks
Thanks for another great video. I appreciate your not giving up. I'm looking forward to a follow up video when you find the problem. This is a tough one.
Got an 8 horse Tecumseh powered snow blower from the early 2000's that misses under no load, when the temperature goes above freezing. I run 91 octane, ethanol free in the machine, makes no difference. Never bothered to look into it, because well, it's a snow blower. Situational and seasonal usage (and is stored with the carb drained and tank bone dry every spring, and she still starts on one pull, will idle all day with the choke fully open, 20 years later, carb never cleaned!)
Got a 5000 watt generac with 8 hp tecumseh. Bought it reconditioned in 1989 after hurricane Hugo. Ran it for two weeks solid then and sporatically ever since. Used it during hurricane mathew and florence. Has always started first pull, never had carb off, drained of gas between uses. Always starts first pull even after long storage. But it has that miss but not as bad. D
Nice to see you using the adjustable wrench in to correct way. I suspect that not too many people understand the stresses on such tools.. Love you work and, admire your skills.
I have the same basic Tecumseh engine on my snowblower (just the winterized “Snow King” version) and it runs exactly like that. Pops and misses a little when sitting with no load, but runs smooth when it gets down to business under a load. Tried everything in the book and never could get it to smooth out under no-load conditions, and I’ve been working on small engines since they still had points!
Clean the magnets on the flywheel! I have the same generator. It would start up great, but then backfire out of nowhere, or just start cycling randomly. I checked for sticky valves, air leak, it sounded lean. Plug didn't really show that. Put a older adjustable carb on it, sounded great and then started doing the same old thing. I thought coil was breaking down when it got hot. I've worked on some Kohler cv engines and that's exactly what happens on those. Worked on countless tecumseh engines, points and Solid state. I could roll that engine by hand and get spark. I checked the air gap between the coil and flywheel but never adjusted it or cleaned anything. Mind you this was only light rust on the magnets. Gave everything a blow with the air gun one day and thought might as well clean up the flywheel. Took Emery cloth to the magnets and wiped a little bit of fluid film on top maybe just to keep it from flash rusting. Cured! I can't believe it was that sensitive. I guess moral-of-the-story is never Overlook the obvious!
I think this is the second time one didn't turn out like you hoped (yet). The other one was your buddy's whole house generator that was a no go. I like watching your thought process on these. Fine line on how much money and time you want to throw at this one. Good luck!
Well said, i have had several of these projects come through, and when your done, can you get the investment back ot of it, and it last more than a couple years, great video, there are alot of these engines out there
@@philliphall5198 .005 to .0010 might be just a tad much, but as i mentioned earlier, it usually only takes about .003 to get it spot on, otherwise you may run into spring bind.
HI Jim: I had some of those Coleman gen sets years ago that had a rear rotor bearing failure. Sometimes they were covered in warrantee. As far as the engine goes, some of the Tecumseh engines don't run to great until under load. Maybe a better spring on the governor might help stableize the engine better. Thanks for a great video.
I'm certain that this solution I'm about to give has already been stated to you. This happened to me on a mower. I had an intermittent misfire, similar to what you experienced. I checked everything and just couldn't find it. I was 100% sure that it was electrical and guess what? It was. But, nothing that I had experienced before. The issue was the kill wire. If you think about it, it just doesn't make sense. But, considering the time that I already put into, I figure that I should continue down a road that I was sure would end in disappointment. Much to my dismay, I found the issue. I unplugged the kill wire and the misfire stopped! I pulled the fly wheel and found the issue. The kill wire was rubbing against the underside of the flywheel. When the engine was cold/cool it ran pretty good with only a small amount of misfire. But, as it warmed up, the misfire would continue to get worse. The wire was bare on one side and cracked on the other side of the insulation. I replaced the wire and voila, the misfire stop.
At 1:02:42 James, you show a shot of the valve seats and what I can see is, what looks like the exhaust valve seat is oval shaped. When you tried grinding it in, the valve was still bottoming out on the follower. You should have taken some of the stem before attempting to grind it. What I think is happening is the gasses are are getting under the valve and lifting the valve when it's running, but not when you're doing the compression and leak down tests.
@@barthanes1 If the rings were leaking, you'd see the gases passing the rings coming out of the breather Bert. Also, you see a flame coming from the exhaust every so often which is the other clue.
One thing that I found for scraping gaskets. I was a carpet layer by trade and used a carpet trimmer. It used blades like a utility knife except they were chisel blades. Bevel on one side, flat on the other. This forced the trimmer down when cutting. When scraping gaskets you can lay the flat side against the surface and not gauge. I found this when I ran out of utility blades. Called carpet trimmer chisel blades.
Reading a few other comments about camshaft and de compression damage from the tight valve clearance I would be leaning towards checking that I really respect how much time you put into thiese old engine sits great to see so much effort put into making them run great again ! Brilliant video love the real in depth trouble shooting videos it's easy to watch for 2 hours plus ! Keep up the great work
I thoroughly enjoyed the video. Fortunately for me, I’m home with pneumonia and have the the time . I’m at a loss as well as to the problem. Please do another update video, all your subs are waiting breathlessly for it, none more than me. Pun intended 😀
i have a couple tecumish 10's. i'll be saving this video in the event that i need to revert back for instruction if either shows the symptoms. ty for this wonderful video
I really enjoy your videos, man! I’m a novice at small engine repair and so watching your content feels like I’m being familiarized with the basics and offers me a wide amount of foundational information to then use when I’m tinkering on my own projects.
The reason you need to run with choke on on your original carb , was due to bad placement of the float bowl when you put it back together,you didn’t Aline the float to the drop in the bowl at recessed place , so in turn it wasn’t allowing the float to drop far enough to allow proper fuel flow thru the needle valve into the float bowl at higher speeds, and which caused the need for the choke usage. Also the value lash problem didn’t help it as well but you took care of that part. Just thought I let ya know what I noticed when you reinstalled the float bowl on the first carb after cleaning it :-)
I can only think of two things. One has to do with the coil breaking down or grounding issues with the coil. The other one could be a defect in the casting or a slight crack in that aluminum mount for the carburetor that could be leaking vaccuum.
This was like watching an Ali / Frasier fight, where both fighters are going toe to toe and trading blow for blow and ending in a draw. However, I know you will figure it out.....with that said, I believe your comment about the engine being worn out after 3 or 4 decades of use is the correct diagnosis. The paint job came out really nice too. Excellent video and I learned a lot! Thank you James for your tenacity!
Lots of work there. I didn't notice you cleaning the very small hole in the lower brass nut that holds the bowl on. It's almost impossible to see. It goes in on an angle about midway on the brass nut it's so small you will need tag wire to clean it. Most carbs also have 3 transfer holes that lead to the side plug. Another thing the engine seems stable for a short time. The Techumpsy carb has a rubber needle valve seat that likes to swell up it maybe restricting fuel flow.
Great video, excellent troubleshooting and testing as always, pretty strange issue with that engine. Hopefully you get it figured out, nice work James!
With this type of content, the longer the video the better to be honest. Sure seventy hours would be too much, but 1, 2, 2.3, even 3h ish for this kind of content just feels right.
When doing a small engine I always clean the magnets on the flywheel of rust and the rust off the coil pickups as well. Rust is not a good conductor and can impart resistance to your pickup dropping performance at load and higher rpm. Generally not a show stopper but often gives a weak spark.
Great flathead motors when they work! That magnetic test light is awesome, He needs to get it patented if he didn't already. That muffler looks like it came off a lawn tractor.
We had that same generator. It was ungodly loud. We bought that same muffler to try and quiet it down. It’s been years, but I seem to recall it was a Tecumseh part/ kit.
Just a point if you are checking for a leak test use a oil can with ATF in it squert all the sealing around the fuel system When it is running it will suck the Atf in & blow white smoke from the exaust.Good luck with the miss.
This was an interesting video. I had to wait until I had enough time to pay close attention, but I don't mind long videos at all when you are dealing with an unusual issue that doesn't have an obvious solution. I love learning new ways to troubleshoot. That is my weak point, so I love stuff like this.
Once you first got it started and found it was producing electricity, you should have just repowered it with a predator engine. I do appreciate your persistence and attention to detail. It was a very interesting video.
PS: Look between the laminates on the old coil pickup arms. Often you will see minute rust jacking the laminates apart. Again weaker field bit less spark. I also wipe a bit of ignition rated silicone grease on the flywheel perimeter, just a bit. Just a hint to hold back the corrosion, especially in a wet application or one that lives outside. I have also seen the coil plug wire have a break in the conductor which after heating up will open up. Inside the insulation so that it isn't visible until you slit the wire for an autopsy.
Back in the day in the Marine Corps when we covered everything there was to cover....we blamed the framulating mucket valve. Seiously though, what a valorous attempt. I would have been reaching for my BFH. Loved watching the entire video and subscribed in hopes of a follow up. 🧐
Reading the comments, the idea of a weak spring makes sense, it could explain the leak test at low pressure. Checking the valve steam diameter clearance can be a good idea too. Maybe it is getting tight when the engine is hot and becoming more difficult to close at low pressure (low load).
Great video; even at 2+ hours I was disappointed when it ended. No video of yours is ever too long. I've seen some comments below (and you've mentioned the same in other videos) that you may want to at least rule out the "missing" air cleaner assembly as a contributor during testing. It's plausible, although the symptoms are more erratic than I would expect for that condition. I'm restoring a 20-year-old 8HP Tecumseh-powered chipper, which is presently 100% disassembled in a box. This video provided lots of tips, and I'm looking forward to your next video on this project as further help as I work to rebuild my own.
I love the way your brain works! And I can't tell you how much I appreciate this video! My good man, you saved my Ariens snowblower.... and for that, I say THANK YOU SO MUCH!!!
depending on the year, you should give the carb a shake to make sure the metering rod is free (sealed part in the chamber parallel to main jet ) was a huge draw back of Tecumseh engines that sit like snowblowers. always ran better than most engines though in my experience when good. When it isnt free, tuning is unlikely not sure if you did it off camera or i missed it, but need to go back and forth tuning from idle to full a couple of times to get it to run good, I usually tuned the to an occasional pop with no load, but i was usually fixing snowblowers in the middle of summer. It is a good daily driver engine, not a good sit until needed engine lol Also agree with a comment on the decompression system might be damaged partially but i would start with double checking the carb.
g`day james i am going to take a guess at a sticking cam follower or valve guide because as you showed something closes at low pressure on the leakdown test as pressure rises and overcomes it and when the engine is running and getting hotter it may be floating the valve (sticking for a moment) . as a flame came out the exhaust i will take a guess on the exhaust side is leaking the air i also thought the decompresser might be sticking hope you do the follow up video to see who guessed right lol.. i like the longer video format great video james cheers
Seriously I love that you don't make your videos short! Please never change that. It's one of my many favorite things about your channel, the other thing I love about your channel is how much depth and attention to details you put in and you're extremely skilled at working on small engines. Your content is pure gold. Thank you for your time and pubic service to your viewers don't ever change how you make your videos ☺️
Agreed!
Pubic service….hilarious
Yes, I am also perfectly content with long videos! Keep them going.
@@stevevogelman3360 in a way it is kind of a public service he’s doing this to help people, you don’t have to be a jerk
That was absolutely worth 2:15 of my time. I have a similar unit that has been under the bench taunting me. After the comprehensive video you put together, even though the machine is not 100%, I gained enough knowledge to give mine another shot. I appreciate that you took the time to show almost everything. You presented fuel, spark, timing and compression and gave each one it’s due. No one can do that in 59 minutes. Your length of video meant you could show all the complexity, and you share your process and you thinking. That is where your content has more value than most. Thank you for this video. It gives me confidence that I can try to take on a similar challenge. You have helped me a lot in the past and you continue to do so here. 6 Stars, on the 5 Star scale.
I totally agree!!! I love these longer videos!!!!
I completely agree. It was worth every last second!
O
Are usually Speed the video up when I watch these unable to get through them a lot faster and if I need to I can always rewind.
I worked on small engines at a rental company. I have seen coils weaken after they warm up.!!😉
I was a mechanic for years and eventually owned a small engine shop when this engine was new. My shop was a master service dealership. I have 2 comments. First these flat head Tecumseh engines never were known to be smooth runner's. . 2nd your not considering a sticky governor. Start with checking the governor rods. For abnormal bends , and spring condition, some models in the series also had a secondary spring. To help stableize movement of the governor rod. It seems you covered all the other likely conditions well.
The governor problem would also explain the hunting at low engine speeds.Sticking flyweights could cause erratic running but I don't know about a high speed misfire.
Those things shook like Hunter Biden when he runs out of crack. Poorly balanced in my experience. That being said i don't think some had carb's matched properly. many used that offset flywheel key that could roll over but not shear and throw the timing off.
😮@@a4000t
The non standard exhaust may be causing back pressure issues (not enough) and the misfire.
@@kevinmills5293 I was thinking the same thing. Running out of suspects ...
Length doesn’t matter when there is good content James I love going through the trouble shooting with you and the group
That’s what the wife says, length doesn’t matter as long as it’s good content.
@@scottdavis9442 🤣
How deep you plow doesn't matter, it's how long you're in the field.
I could listen to the guy all day.
I had the same problem and it was trash I the carburetor
You're not alone. I "had" an 8 hp techumsa with exactly the same issue. It was on my log splitter I owned for 20 years. Because it would "run" crummy I just let-err-rip spit & sputter while I split wood. Every year or two I'd try fixing it. I did everything you did 10-times over 20 years. My carb was NLA & the closest carb I could get was for a generator. That didn't fit or work well at all. I bought every carb part available for my engine. What I ended up doing that fixed the hard starting & running ruff was....the little brass screw in jet on the top side of the carb ..... I used a finger drill & made the through hole (not the tiny side hole) larger one drill size at a time. That finally fixed it - Yahoo & sold the log splitter. I ever see another 8 hp techumsa I'm not fixing it - whatever it takes to replace it would be a shortcut. Grrrrrr8 video 👍
that would make sense as he mentioned he has to run at half choke through most of his video meaning he has to cut down on the air supply. Could mean he isn't getting enough fuel? hmmmm
Most people today will dump it and head to Harbour Freight.Time and money saved !
I have that log splitter. Leave it parked in the barn for 6 years with fuel in the tank and pull it out leave it all winter covered with snow. Put fresh fuel in it in the spring. Hit the primer 3 times and start it. Seems to have been what mine wanted. Runs better now than when it was new.
A two hour fix it video first thing in the A.M..
I like it!
James, I had a Coleman generator like this and it ran the same way from new. It ran fine under load but stumbled occasionally when not under load. I never got it figured-out. I appreciate your efforts and don't mind the length of this project, this is the second time I've watched it and have learned more this time around! Keep up the good work.
I know it's not the same application, but when I used to maintain a fleet of pushmowers and other motorized small engine equipment, Tecumseh always proved to be problematic for weird things like this. They were always the more tempermental units to get running and even then, they would never act really *right* when compared to B&S, Champion, and other small engines of the same form factor. I'll be watching to find out what you find out in your investigation, but that's definitely a head scratcher. From what I can tell,. you've gone above and beyond, this thing should be running like a top by now.
Another great video James ,2 tricks I use. Valve lapping suction cups are prone to not sticking very well, I now use a 3/4" dowel and stick it on with hot melt glue , works great. The other trick is when grinding the valve stem use a vernier caliper to measure valve length before grinding.
Saves putting valve in and out of the block to measure the clearance.
You get top marks for persistance.
Thanks for the tips.
@@jcondon1 You can use a few drops of rubbing alcohol where the glue meets the materials and it will cause the glue to pop right off!
Yeah I thought about hot glue
Great tips! 👌
When doing valves, I also use double sided foam tape, but instead of using the valve tools as shown, I use a piece of dowel wood. It works great. I never have issue now doing valves. I get them done easy as tying my shoes. The dowel never slips off till I remove it from the two sided tape and I can apply far more pressure while spinning the valves and not have them slip. I threw my valve tools away.
I think you may have a valve floating issue. Weak valve springs will do that. It would explain your higher leak down at lower pressure as well. While you did lap the valves in, your exhaust valve may be ever so slightly warped or bent as well. I'd try some valve springs.
definitely a possibility
Jim,
During the 1980s, Kohler had a reoccurring problem with valves or valve guides.
Similar symptoms; but, with additional occasional caveat!
The exhaust valve would stick in the open position, until the engine cooled.
The engine would suddenly die, and have no compression for several minutes. Eventually there would be a LOUD snap, and could then be restarted with ease.
Thus, As did MarkholtropXXXX (9 months ago), I suspect a bent or warping exhaust valve.
Once, we cured the problem in an Allis Chalmers Garden Tractor, by cleaning/reaming the valve guide. That unit had replaceable guides, but we lacked ready access.
Nanci 😂😢😮😅😊f
I can't believe I watched all 2:14 of this! That's a testament to the quality of your content, your vast knowledge and your determination to get things done right. Your video definitely did help me. I now know to avoid alllll things powered by a Tecumseh! Ha! Some of your other videos have definitely helped me rehab a Briggs carburetor. Thanks a bunch and keep them coming.
ah you gotta understand though one engine having issues isnt a reason to avoid that brand
Nor can I! It was just watching this man's sheer determination. I have to give him full credit for his perseverance. Thank you. And endeavours.
James, have you considered tired/week value springs. The compression will test good, but week springs will not follow the cam accurately at speed, causing the intermentent misfire you're experiencing. Take them out and measure their height. And while they are out, clean the carbon and lap. Good luck. Really enjoy your videos. They are a part of my weekly must-see video list on RUclips.
I have had some similar issues before, I always go to the coil where it mounts. I remove it and clean the mounts on the block and clean where it mounts on the coil, then I use a little silicone grease before I regap the coil. It fixes the problem about 50% of the time. I hope this helps you your videos are very helpful especially on the generator side.
Forgot to mention that, but did clean the coil mounting location and the old coil as well where it meets the block.
To prevent the tank from getting hot due to heat shield being to close place a spacer bar to raise tank up higher above the mounting bolts with spacer material
@@michaeltarasenkoop2389 I have used heat shield material as added protection.
Did not read all the comments but what about the lobes on the cam shaft ?
@@Mrcrowley1967 This is the comment I was looking for!
Ha! I have not seen you working 4 hands. It was a lot of work but the end justified it. Thanks for sharing! Stay healthy!
Compression ring with low tension, or weak valvespring(s), those are my guesses. Both would show better performance under load for this small engine application. Anxious to see the follow up on this one!
I was thinking weak valve springs too.
Hi James, to get burning gases out of the exhaust can only be a few things. Bad ignition timing I.e too late, sticking exhaust valve. Excessive un atomized or large particle fuel in the combustion chamber. An interesting experiment would be to run it on LPG or NG as the fuel is already in a gas form. This would eliminate poor carburation. Fuel injection would have a similar effect but hard to do on a budget. Some newer B&S engines have fuel injection now. We deal with 100’s of small engines at work but mostly Honda and Lifan Some Kolhler and Kubota and B&S. Interesting issue I would love to get the scope on to try and see what is really going on. You could try a video of the valve operation and then view the video in slow motion to see if there are any anomalies.
I bought a Troy Built tiller with an 8 HP Tecumseh back in the 90's. I still use it and it runs about the same as the one in this video. I gave up years ago on making it run smooth. My suggestion is to move the engine to your garden tiller. 😄
lol
An easy way to check for vacuum leaks, or to check the fuel mixture is with a propane torch. By turning on the torch without lighting it you can introduce the propane gas into the carburetor and it will change the mixture without actually adjusting the carburetor. You can run the motor at the problematic RPM and see what changing the mixture does. This helps isolate a fuel mixture problem. By using a torch with a rubber hose attached, you can look for vacuum leaks. This eliminates spraying flammable liquids in areas where it would cause trouble. It looks like when it is backfiring flames are coming out of the muffler. My guess is the exhaust valve is sticking. If it was rings you would see excessive blow by out the crankcase breather. I didn’t see what condition the spark plug was in, but I would make sure it is the proper plug. I would replace it. I have seen spark plugs do strange things.
After i just found this video and watched it,i can see what my grandfather said was essentially true,he worked at GM for 40 years and knew his way around engines and such,he owned numerous Tecumseh powered yard equipment tools over the years,and what he said was "they (the Tecumseh engines) like to be put to work" and now i realize what he meant,also fantastic videos,keep it up John!
When James fails, the viewers win. I love long-form vids from you.
I have a 13hp Tecumseh on my lawn tractor. It uses the same type ignition coil. I used a timing light to check timing, they run it at 30° before top dead center. Some engines miss under light throttle with this much timing, I suggest trying an offset flywheel key if you find out your ignition timing is as mine at 30°. You can use a battery powered timing light to check this and mark the screen behind the starter with a chalk line at top dead center.
My Briggs & Stratton generator only runs the timing at 0° top dead center.
That's a lot off turd-polishing for very little return! The best part about things that are hard to troubleshoot, is when you do finally figure it out and get it going.
I don’t know the first thing about small engines except how to use them. Your methodical approach and excellent narration kept me captivated all the way through. I hope you sorted the problem for your own sanity.
Yes!
james has been doing so much for so long with so little, that he is now qualified to do anything with nothing
Looks like he has plenty of tools to me
For ever!
@billhenry7833
😂
Hi, Jim…as you know, my field of expertise was electronics and not gasoline engines. When you made the initial test for spark I observed a really strong spark appearing on your tester. This got me thinking of possible leakage from the secondary of the coil to ground intermittently, or even from the spark plug wire itself. I used to see this happen on the secondary side of flyback transformers in older televisions that I used to repair which provided the high voltage to the CRT. Sometimes, the insulation on the second anode lead would fail and cause intermittent arcing to ground. They made a substance called Glyptol in a spray can that could be applied to the entire transformer and second anode to restore the dielectric properties of the high voltage system. It sure looked like that could be your issue until, at the end of the video, you showed where you actually replaced the coil, which pretty much blows my theory to bits. When you’ve gone through everything as thoroughly as you did and eliminated just about every possibility, you might consider a manufacturing flaw in that specific unit, one that is so small that it’s impossible to detect yet significant enough to cause the misfiring.
Good try, pal. At least now I know you’re human! 😂 You’re still the best I’ve ever seen, very helpful, and most entertaining.
I think your right I seen that too.
Your scenario was plausible indeed, until the coil replacement. If one could start the engine with the cover off and observe, perhaps we would learn something.
It could be sparking at the shutdown tang because that still has relatively high voltage pulses on it and is out exposed in the elements. It was even painted over which could be trapping dirt or moisture.
Could be kill switch wire it self dry rotted insulation or arching intermittent.. causing intermittent missing
Yes that's possible. This engine also has a "low oil shut off switch" which may be bouncing on and off too.
Even though you haven't solved the problem yet, this was an awesome video. I ALWAYS learn from your videos and it was absolutely worth 2:15. Great job! I hope someone comes up with an answer for this.
A great video. One suggestion is when watching for spark using light, record the spark light at high speed and watch back. At 400 frames per second you spot the missing spark.
don't worry about the money you throw at it , look at it like you paying for a education, its an education we learn..if you dont sell them you could always rent them out..great job as usual.
I mean this sincerely, thanks for the long video. Loved it and so much work on this one.
I agree
Your videos are never too long, regardless of the outcome. I learn something from you every time, You are a BOSS!
One thing you didn't do for most of the testing is have the air cleaner on. The air cleaner creates enough drag to affect the mixture, possibly making it too rich. You may try retuning the carb with the air filter installed, because it can change how the engine runs significantly.
Your probably right, especially with Tecumseh engines. There's a reason Tecumseh went out of business, those Chinese Honda knockoffs are assembled with far more quality.
@@brianallen9810 they didn't go out of business. They were acquired by an investment firm, and still manufacturing parts, and have a number of engines in stock.
Better check Project Farm from last week on YT before you think they are better than Tecumseh. One they tested used almost half of the engine oil on a 24 hour test. They also produce more carbon monoxide than the Honda engine in the same test. The predator engine was a little bit better, but not better than the Honda engine.
@@brianallen9810 I'd have to agree on Tecumseh engines, I've never personally seen one that ran correct. My dad has this exact generator and it has never ran smooth. There was a old guy in my town that had a old rear engine John Deere mower with a Tecumseh engine and he constantly fought it for years. One day he pulled up to his house and idled it down and it threw the rod out of the block. I went to our local scrap yard and got a 8 HP Briggs and stratton and put on it. He said he just didn't know what to do with all of his time since he could just go and mow and not have to adjust the carburetor on the Tecumseh. It was still running when he passed away years later.
@@littledave601 yeah Tecumseh motors are good for either pouring oil like a siv wanting to run pretty much wide open no matter how you try to tune them or they will randomly chuck the rod out the side without any warning what so ever every one I have delt with has been like that so when get something and it has one of those on it the first thing I do is pull it and send it to the scrap yard and replace it with a good old briggs
That's a good possibility, on motorcycles it happens more than people would like to admit. Same on some GM vehicles with the MAF sensor built into the air filter housing. No filter, bunch of weird A/F related codes.
Any time you remove the head on a Tecumseh engine it is always a good idea to take an indicator and check the timing as just a change of .001 thousandth of an inch on the points can make a change in the timing. I owned and operated a shop for several years and was a certified repair and warranty center and found this to be a common problem.
I was thinking what about the points and condenser when he removed flywheel to check the key. Tearing that far down, I always checked to see condition of the points if they have a burn spot on it. Plus, I might look old with a long white beard on outside but the kid in me loves to charge up the condenser from the motors when I put new ones in. Then sit it on the table and wait. When you hear a yell you caught one. They always just need to pick it up and look at it to see what it is. Touch wire and housing at same time with bare hands and win the prize. I use to set out about 10 to 20 per week back in the 1980s. Ah the good old days. An I know alot of you reading this did the same thing. Great minds think alike. Just like grabbing a electric fence a only hold it for half a second an say nope it's not on. Then someone else always has to check it. Bigger yell. Hahaha. We had so much fun but nobody got hurt, we did get some good deep scars back then but most have faded since that time. Great video buddy. Stay safe, wear rubber gloves.
No points on this model engine. Electronic ignition.
@@terrydouglas2777 Hi, when he had the flywheel off, there are no points or condenser. Tecumseh is using the B&S points eliminator coil. It has a trigger coil and a couple of npn transistors to start the electron flow and then interrupt it. So, no points on this setup.
@@baratono lol I know, wtf. Also .001 on the points would not make a difference in running anyway. It's not rocket science. It's a old school engine, they aren't too picky.
Working on a hm100 on a 5000 watt devilbiss gen, same problem exhaust valve no clearance, did valve job new head gasket, then carb same issue exactly misses at no load, but under load good. Compression 60+, will check coil and wire but beginning to think about weak valve springs or low oil sensor problems.
Thanks for the good work.
Ha ha, I saw your black kitty sneak on by just b4 the valve cleaning...like maybe he won't notice...lol
Are any of us going to suggest a “cat” scan now?
@@onepeanutwhistle5232 You just did! 🤣😂🤣
@@onepeanutwhistle5232I’m still waiting on the Lab results.
The big clue here is it got worse with a new plug
A stronger spark could produce a higher pressure on the power stroke because of better fuel combustion which
could aggravate a problem with the valves having a weak spring and bouncing when closing
I have read all the comments and concluded valve spring pressure is the most probable cause according to popular opinion
I’ve never seen a new plug make things worse in any engine! That’s very unusual! ( just saying) 😀
I wonder if the gap size was the same between the old and new plugs too
Valves bouncing when closing?! I never would’ve considered something like that. Hopefully, whoever was the first to diagnose that got a medal
Hey James, love your videos! I haven’t read through all the comments, & I know this video posted 7 months ago. Perhaps you’ve already found the answer. Based on 25 years experience, I think the intake guide clearance is excessive, causing the cylinder to pull air out of the crankcase. Especially when the engine has the most vacuum ( idle & no/light load at rated rpm. This also explains the hard/erratic starting. Went through the exact same thing with an HM80. Ran great under load, couldn’t make it idle properly, did everything as did you. Intake to guide clearance. Tecumseh makes 1/32” oversized stem valves.🇺🇸😊
Since you checked almost everything on the engine side, please check the generator side. If there is an intermittent short within the generator, it will introduce a brief large load on the engine. At small speeds this could be impacting the engine.
Connect an oscilloscope to the outlets and check if the wave is stable.
I had a bad bearing on the output side of an old Pincor that was causing a similar issue when it would feel like getting sticky for a second
The output waveform wouldn't be stable with a misfire anyway.Any brief interruption of engine speed will distort the waveform.
good work on sticking with it👍 i’m thinking it could be a sticky valve at you stated or maybe the decompression possibly malfunctioning.
May want to check the cam, if the cam is a bit "wobbly" it will cause these intermittent and sometimes unreproducible issues. Though it mainly affects Briggs engines from the late 2000s where the cam shaft comes loose from the gear, but there may be a burr or something like that on the cam lobe or a sticking lifter/tappet.
You really did battle this one, it so happens I learned small engine tuning on Tecumseh and they are very forgiving about carburetor settings, I have found a new spark plug helps even if the engine still runs on the old one, nice job James
Real great effort on your part here James. The length of time a video lasts is not an issue. In fact with a shorter one I'm wishing they were longer. I thank you for all your content however it comes to us.
Yes!
Let me reiterate: it works well under load and that's when you need it working the most. Perhaps it is a tolerance issue in the manufacture of this engine, or there is another worn part somewhere in that old engine. Thanks for the great videos. :-)
Using the roloc brush is always satisfying, never gets old, thank you Mr. James.
what you can try is cleaning the mounting bosses for the coil and the two contact surfaces for the coil to the Block, you may have high series resistance between the coil body & the engine which might cause inconsistence spark especially at high RPM's. I would also wire brush the circumference of the flywheel to get ride of any rust which can be affecting the coils response. Also Tecumseh engine are notorious for bent valves so you can test it by placing them in a drill and spinning to see any irregularities, an intake valve leak would sure give you that issue too but it may not show up on a leak down test but more so when the valve lifts & rotates under normal operation..
Good idea with the 2x tape👍🏻 I don’t think I’ve ever not heard them old Tecumseh engines not pop and miss no matter what they were on. They hard to kill if maintained.
I have this same engine and after a few years, it exhibits the same exact behavior as yours. Mine is used to power a chipper shredder. I followed the same exact path you did in the video several times over the years but was never able to get rid of the misfires either. It’s the only engine (I have probably 15 or so engines across all the brands) I was unable to bring back to perfect. Finally, I set it aside and swore to myself I would not waste any more time with it, lol. And, I’ve never bought another device with a Tecumseh engine on it either. Crazy engine for sure. It will be interesting to see what you find if you open up the lower engine.
I am with YOU! I HATE them! I wouldn't swap a Briggs or Kohler for their whole factory. OR Robin!
I got a free Craftsman mower with an older like 13 horse Briggs flat head. Originally i messed with the carb, nice and clean, it started PERFECTLY, ran ok but had like pops. Carb adjustments did nothing, kind of leading me to beleive carb. Also was blowing a good bit of air back through the carb. Thought it was weird, already had a new plug just because its cheap and it looked original on a 15 year old mower. Checked and the intake valve was not sealing and leaking compression, zero lash either. Got a gasket ect, lapped the valves, adjusted the lash to spec, everything should be good, yes? Well now when i adjust the carb it actually does something, still pops, it will go and run, just it doesn't sound as nice as it should, being everything is so nice and perfect. Annoying spending the time, not because it doesn't work, but because you want it perfect and it didn't really help. Not gonna throw it by any means, but its something else.
@@baileyhatfield4273 I've got one like that that the governor is very sluggish on. An 85 model 4 horse flathead with an 'all climate' carb on a Snapper 21. Didn't make many and info is less. I got a real Briggs book for all flatheads from 86 on I think but hardly anything on that engine but even less on the carb. I think i have an angle on it but will have to wait to see. Never had a Briggs to run sorry. Tecumseh? OH yeah. IF the mower had a hood scoop to pull fresh cool air in through slots in the hood to the motor intake screen and it's gone, rig one back up again. The hot air gets trapped under the hood without the foam between the hood underside and engine and it gets way too hot. I also run DELO 15/40 Diesel formula lube oil in all mine and my truck. Thicker oil lubes better and cools better.
Wow, getting old school there. Almost in line with a Model T lol
2 hrs and 15 minutes of my life I'll never get back. Thank you, Sir, Mr. Government Engineer. Try starting with the least path of resistance. Definitely an hr government employee " Engineer.".
Nice job James! You are bringing all of us together with thinking caps on. Several things come to mind because the engine does seem to run better cold. First, fuel boiling in the carb bowl (winter gasoline can and will make this worse). Second, the exhaust valve sticking or compression release malfunctioning. Third, pre-ignition reducing the spark plug heat range. If I know you from all your videos, you don't give up unless there is an obvious flaw. I do recall more than one person installing a 8HP Tecumseh from a junk snowblower (the engines all ran great in the winter) on a log splitter which all ran like crap on the log splitter. (seem to run lean and back-fire when hot)
Hi james.great video as always, I’m actually leaning towards the compression release tap on the camshaft, in some cases when the exhaust valve clearance is too tight that can cause the tap on the camshaft to bend and consequently causing afterfire from the exhaust. Hopefully it will be easier then that and Good luck 🍀
James … have you ever used a sledgehammer on a project like this?
That is a good idea. It would explain the odd leakdown.
Strange glitch at low pressure on your leakdown test. Assuming your gauge valves are not the cause I'd suspect a broken ring or ring land damage on the top side of the compression ring. I had a rototiller with the 10 hp Tecumseh and which ran similar to yours. The plug in leads for the coil were shorting intermittently to the head when up to operating temp resulting in stalling miss. Thx for the great videos James !
James, I usually watch your channel on my television, but that prevents me from commenting so I'm using my laptop. Just wanted to thank you for putting so much time and effort into your videos. I typically do my own small engine work, but I have learned so much from watching your videos. I can't thank you enough. I have even upgraded a few of my tools after watching. Thank you again for such detailed and complete videos showing diagnosis and repair!
Thanks for the positive feedback. I appreciate it.
I admire your persistence - It's heart-warming.
I try to never let the value of my time exceed half the yard sale value of a project.
"It's a Tecumseh - It's part of the charm"
"It may sound like shit - But it starts every time and will power things up"
"You'll get used to it" :)
Thanks for all your efforts and these long videos. I like all of your content and especially love the thorough analysis and well done video quality.
Yes!
Always enjoy your diagnosis and progress on repair of small engines. Over the years, I have worked in mine and my neighbors. Managed to keep them going. Your videos have sure helped. Very good tips. Thanks
Yes!
I'm really looking forward to Tecumseh Season 2, I love the breakdown in each episode.
Thanks for another great video. I appreciate your not giving up. I'm looking forward to a follow up video when you find the problem. This is a tough one.
Got an 8 horse Tecumseh powered snow blower from the early 2000's that misses under no load, when the temperature goes above freezing. I run 91 octane, ethanol free in the machine, makes no difference. Never bothered to look into it, because well, it's a snow blower. Situational and seasonal usage (and is stored with the carb drained and tank bone dry every spring, and she still starts on one pull, will idle all day with the choke fully open, 20 years later, carb never cleaned!)
Got a 5000 watt generac with 8 hp tecumseh. Bought it reconditioned in 1989 after hurricane Hugo. Ran it for two weeks solid then and sporatically ever since. Used it during hurricane mathew and florence. Has always started first pull, never had carb off, drained of gas between uses. Always starts first pull even after long storage. But it has that miss but not as bad.
D
Nice to see you using the adjustable wrench in to correct way. I suspect that not too many people understand the stresses on such tools..
Love you work and, admire your skills.
I have the same basic Tecumseh engine on my snowblower (just the winterized “Snow King” version) and it runs exactly like that. Pops and misses a little when sitting with no load, but runs smooth when it gets down to business under a load. Tried everything in the book and never could get it to smooth out under no-load conditions, and I’ve been working on small engines since they still had points!
Clean the magnets on the flywheel! I have the same generator. It would start up great, but then backfire out of nowhere, or just start cycling randomly. I checked for sticky valves, air leak, it sounded lean. Plug didn't really show that. Put a older adjustable carb on it, sounded great and then started doing the same old thing. I thought coil was breaking down when it got hot. I've worked on some Kohler cv engines and that's exactly what happens on those. Worked on countless tecumseh engines, points and Solid state. I could roll that engine by hand and get spark. I checked the air gap between the coil and flywheel but never adjusted it or cleaned anything. Mind you this was only light rust on the magnets. Gave everything a blow with the air gun one day and thought might as well clean up the flywheel. Took Emery cloth to the magnets and wiped a little bit of fluid film on top maybe just to keep it from flash rusting. Cured! I can't believe it was that sensitive. I guess moral-of-the-story is never Overlook the obvious!
Will give it a try
I think this is the second time one didn't turn out like you hoped (yet). The other one was your buddy's whole house generator that was a no go. I like watching your thought process on these. Fine line on how much money and time you want to throw at this one. Good luck!
Well said, i have had several of these projects come through, and when your done, can you get the investment back ot of it, and it last more than a couple years, great video, there are alot of these engines out there
No big deal just shim the valve springs with.005/.010 shims
Fixed it. New spring are to weak to
@@philliphall5198 .005 to .0010 might be just a tad much, but as i mentioned earlier, it usually only takes about .003 to get it spot on, otherwise you may run into spring bind.
HI Jim: I had some of those Coleman gen sets years ago that had a rear rotor bearing failure. Sometimes they were covered in warrantee. As far as the engine goes, some of the Tecumseh engines don't run to great until under load. Maybe a better spring on the governor might help stableize the engine better. Thanks for a great video.
I'm certain that this solution I'm about to give has already been stated to you. This happened to me on a mower.
I had an intermittent misfire, similar to what you experienced. I checked everything and just couldn't find it. I was 100% sure that it was electrical and guess what? It was. But, nothing that I had experienced before.
The issue was the kill wire.
If you think about it, it just doesn't make sense. But, considering the time that I already put into, I figure that I should continue down a road that I was sure would end in disappointment. Much to my dismay, I found the issue. I unplugged the kill wire and the misfire stopped! I pulled the fly wheel and found the issue. The kill wire was rubbing against the underside of the flywheel. When the engine was cold/cool it ran pretty good with only a small amount of misfire. But, as it warmed up, the misfire would continue to get worse. The wire was bare on one side and cracked on the other side of the insulation.
I replaced the wire and voila, the misfire stop.
Just picked this one up today for 35 dollar I am so glad you did this video. I'm going to watch this before I even jump into mine.
Why not raise the tank by a inch or more with spacers and add a mineral wool blanket between the heat shield and the tank that will keep it cooler !
At 1:02:42 James, you show a shot of the valve seats and what I can see is, what looks like the exhaust valve seat is oval shaped. When you tried grinding it in, the valve was still bottoming out on the follower. You should have taken some of the stem before attempting to grind it. What I think is happening is the gasses are are getting under the valve and lifting the valve when it's running, but not when you're doing the compression and leak down tests.
I agree. Martin's idea is worth a shot.
You are absolutely correct. Cannot believe I did that out of order. Also as you mentioned the seat did look a little off.
Yes, definitely sounds plausible.
@@barthanes1 If the rings were leaking, you'd see the gases passing the rings coming out of the breather Bert. Also, you see a flame coming from the exhaust every so often which is the other clue.
@@jcondon1 Correct that seat James and I think that'll fix it. 🙂
One thing that I found for scraping gaskets. I was a carpet layer by trade and used a carpet trimmer. It used blades like a utility knife except they were chisel blades. Bevel on one side, flat on the other. This forced the trimmer down when cutting. When scraping gaskets you can lay the flat side against the surface and not gauge. I found this when I ran out of utility blades. Called carpet trimmer chisel blades.
Hey Jim - CONGRATULATIONS on the 100K! Love your channel. Your videos just keep getting better all the time.
Thank you very much!
Reading a few other comments about camshaft and de compression damage from the tight valve clearance I would be leaning towards checking that I really respect how much time you put into thiese old engine sits great to see so much effort put into making them run great again ! Brilliant video love the real in depth trouble shooting videos it's easy to watch for 2 hours plus ! Keep up the great work
Yes!
I thoroughly enjoyed the video. Fortunately for me, I’m home with pneumonia and have the the time .
I’m at a loss as well as to the problem. Please do another update video, all your subs are waiting breathlessly for it, none more than me. Pun intended 😀
Yea, me too, just at home having some fever, but can't sleep until Tecumseh final episode.
i have a couple tecumish 10's. i'll be saving this video in the event that i need to revert back for instruction if either shows the symptoms. ty for this wonderful video
I really enjoy your videos, man! I’m a novice at small engine repair and so watching your content feels like I’m being familiarized with the basics and offers me a wide amount of foundational information to then use when I’m tinkering on my own projects.
The reason you need to run with choke on on your original carb , was due to bad placement of the float bowl when you put it back together,you didn’t Aline the float to the drop in the bowl at recessed place , so in turn it wasn’t allowing the float to drop far enough to allow proper fuel flow thru the needle valve into the float bowl at higher speeds, and which caused the need for the choke usage. Also the value lash problem didn’t help it as well but you took care of that part. Just thought I let ya know what I noticed when you reinstalled the float bowl on the first carb after cleaning it :-)
I can only think of two things. One has to do with the coil breaking down or grounding issues with the coil. The other one could be a defect in the casting or a slight crack in that aluminum mount for the carburetor that could be leaking vaccuum.
Yes, a minute hole in that pipe might be it.
Thank you for a really absorbing evening's entertainment. Puts my last few weeks trying to cure a 30 year-old Farymann diesel into perspective!
This was like watching an Ali / Frasier fight, where both fighters are going toe to toe and trading blow for blow and ending in a draw. However, I know you will figure it out.....with that said, I believe your comment about the engine being worn out after 3 or 4 decades of use is the correct diagnosis. The paint job came out really nice too. Excellent video and I learned a lot! Thank you James for your tenacity!
Lots of work there. I didn't notice you cleaning the very small hole in the lower brass nut that holds the bowl on. It's almost impossible to see. It goes in on an angle about midway on the brass nut it's so small you will need tag wire to clean it. Most carbs also have 3 transfer holes that lead to the side plug.
Another thing the engine seems stable for a short time. The Techumpsy carb has a rubber needle valve seat that likes to swell up it maybe restricting fuel flow.
Great video, excellent troubleshooting and testing as always, pretty strange issue with that engine. Hopefully you get it figured out, nice work James!
id suspect weak valve spring being the issue
With this type of content, the longer the video the better to be honest. Sure seventy hours would be too much, but 1, 2, 2.3, even 3h ish for this kind of content just feels right.
When doing a small engine I always clean the magnets on the flywheel of rust and the rust off the coil pickups as well. Rust is not a good conductor and can impart resistance to your pickup dropping performance at load and higher rpm. Generally not a show stopper but often gives a weak spark.
Great flathead motors when they work! That magnetic test light is awesome, He needs to get it patented if he didn't already. That muffler looks like it came off a lawn tractor.
We had that same generator. It was ungodly loud. We bought that same muffler to try and quiet it down. It’s been years, but I seem to recall it was a Tecumseh part/ kit.
I sure am glad you got a lift. We are not getting any younger. Wish I could have had one working on bikes for all those years. Thanks for posting.
You’re an excellent mechanic. Great determination sir! I would have been loading a brand new generator in my truck at Home Depot long ago 😂
Just a point if you are checking for a leak test use a oil can with ATF in it squert all the sealing around the fuel system When it is running it will suck the Atf in & blow white smoke from the exaust.Good luck with the miss.
This was an interesting video. I had to wait until I had enough time to pay close attention, but I don't mind long videos at all when you are dealing with an unusual issue that doesn't have an obvious solution. I love learning new ways to troubleshoot. That is my weak point, so I love stuff like this.
I love the way you grow an extra set of arms at critical moments
Once you first got it started and found it was producing electricity, you should have just repowered it with a predator engine.
I do appreciate your persistence and attention to detail. It was a very interesting video.
PS: Look between the laminates on the old coil pickup arms. Often you will see minute rust jacking the laminates apart. Again weaker field bit less spark. I also wipe a bit of ignition rated silicone grease on the flywheel perimeter, just a bit. Just a hint to hold back the corrosion, especially in a wet application or one that lives outside. I have also seen the coil plug wire have a break in the conductor which after heating up will open up. Inside the insulation so that it isn't visible until you slit the wire for an autopsy.
I would try some 2 stroke oil in the gas at this point to lube the valve stems while it's running and see if it makes a difference.
Back in the day in the Marine Corps when we covered everything there was to cover....we blamed the framulating mucket valve. Seiously though, what a valorous attempt. I would have been reaching for my BFH. Loved watching the entire video and subscribed in hopes of a follow up. 🧐
I'm not sure what you do for a living but I love your approach to fixing things. I would follow some of your same reasoning. Good job.
wow, such thorough troubleshooting and still stumped . a rarity.
Reading the comments, the idea of a weak spring makes sense, it could explain the leak test at low pressure. Checking the valve steam diameter clearance can be a good idea too. Maybe it is getting tight when the engine is hot and becoming more difficult to close at low pressure (low load).
BTW, one of yours best videos. Waiting for the follow up!
Great video; even at 2+ hours I was disappointed when it ended. No video of yours is ever too long. I've seen some comments below (and you've mentioned the same in other videos) that you may want to at least rule out the "missing" air cleaner assembly as a contributor during testing. It's plausible, although the symptoms are more erratic than I would expect for that condition. I'm restoring a 20-year-old 8HP Tecumseh-powered chipper, which is presently 100% disassembled in a box. This video provided lots of tips, and I'm looking forward to your next video on this project as further help as I work to rebuild my own.
I love the way your brain works!
And I can't tell you how much I appreciate this video!
My good man, you saved my Ariens snowblower.... and for that, I say THANK YOU SO MUCH!!!
depending on the year, you should give the carb a shake to make sure the metering rod is free (sealed part in the chamber parallel to main jet ) was a huge draw back of Tecumseh engines that sit like snowblowers. always ran better than most engines though in my experience when good. When it isnt free, tuning is unlikely
not sure if you did it off camera or i missed it, but need to go back and forth tuning from idle to full a couple of times to get it to run good, I usually tuned the to an occasional pop with no load, but i was usually fixing snowblowers in the middle of summer. It is a good daily driver engine, not a good sit until needed engine lol Also agree with a comment on the decompression system might be damaged partially but i would start with double checking the carb.
g`day james i am going to take a guess at a sticking cam follower or valve guide because as you showed something closes at low pressure on the leakdown test as pressure rises and overcomes it and when the engine is running and getting hotter it may be floating the valve (sticking for a moment) . as a flame came out the exhaust i will take a guess on the exhaust side is leaking the air i also thought the decompresser might be sticking
hope you do the follow up video to see who guessed right lol.. i like the longer video format
great video james cheers
Ive had old tecumseh boat motors in the 70s and 80s yeah im old i know,none of them had a electronic ignition but points i loved those old engines
Great job, you’ll get it running correctly, I have faith in you.