Honda CRF 250 Dirt Bike Backfires But Won't Start. What's Wrong With It?
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- Опубликовано: 11 июн 2022
- I work on a 2010 Honda CRF 250R dirt bike that won't start. Let's figure out what's wrong with it. #Honda, #Mystery, #250,
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The following video features activities performed in controlled environments by knowledgeable persons. DO NOT attempt to duplicate, re-create, or perform the same or similar activities at home, as personal injury or property damage may result. 2vintage( Joe Weber, the persons shown in this video and ANY CONTRIBUTOR, ARE NOT LIABLE FOR ANY such injury or damage. ALL 2vintage( Joe Weber) CONTENT IS FOR ENTERTAINMENT PURPOSES ONLY.
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I just want to come and say that.. thanks for all you’re content man, legit I’ve been learning a lot of thinks from you’re videos man. I appreciate what you do just to entertain us and teach us too.
I just found your channel recently and really like how you take the time to explain how engines and transmissions function & the steps necessary to repair them properly. If I lived in Wisconsin near you I would certainly buy a machine you repaired with confidence.
Love your videos man! There's never a video I don't learn something new, thanks!
Kudos to you for taking on other peoples tough jobs. I find that its one thing to work on and fix up my own stuff, but something else entirely to take on jobs other people send me. For me its easy to get in over my head with other folks headaches I agree to take on. Good luck and thanks for sharing!
If you had a problem with the compression release, the leak down test would have shown a leak through the exhaust valves. It's leaking into the crankcase, so it's either rings or a head gasket. Also, when the compression test is that bad, squirt some oil through the spark plug hole into the cylinder and retest it. If the compression comes up, the rings are bad.
the leakdown should be done at tdc so the lobe of the compression release should not be engaged with the valve.
how do you know all of this sir. wow
the oil in the cylinder after bad compression test is a new one to me… will be trying that.
@@isaiahthomas4906 practice
Not all the time … it could be the decompression seating is not set right or the shims for the exhaust is out of clearance
Hey 2 vintage when are you going to do another video? I like watching you work on those things. I also have been wrenching some myself again.& doing other projects between times to. Keep up the good work man. It's really is one big learning experience though on certain things in life right man?
Absolutely love your videos. It’s great to see how you diagnose these faults and set about fixing them. Just pull a few more wheelies on them when you’re done!!😂
Awesome video Joe. Love seeing dirt bikes on the channel.
Joe you have come along way from the first videos, way to go, love it
Love the channel definitely should do more modern and newer bike and atv builds on the channel. I love the modern builds.
This is one of the most thoroughly troubleshoot video that ive seen! Well done!!
The compression release on a small engine accounts for about 30-40 psi of lower compression when testing. Takes at least 500 RPMs to take the compression release out of the equation. Owner had the exhaust valves set tight, not loose. How you are only getting 10 psi on a compression test and little leakage on leak down test is both concerning, and odd. If you suspect worn or stuck rings, simply add some oil down spark plug hole and if compression increases, then rings are most likely the problem. Funny how the owner installs a new fuel injector, sets the valves, but does no compression or leak down test.
Hi joe yeah tend to agree with you mate I think once it's rebuilt it will fire up just fine looks a good bike although not really a fan of injectors much prefer old school to be honest less to go wrong not knocking the bike by any means just prefer carburettor I know what I'm working with lol great video look forward to the rebuild take care 🔧🔧🔧👍👌
Nice bikes when new-ish. When older, they can be a bit difficult to work on and diagnose. This is one of the reasons why I stick with 2 strokes with carburetors for my *personal* machine. They're so darn simple and still tons of fun.
I don't understand how people say carbs are so simple 🤔 maybe never had to tune a brand new one from scratch without the original jet and needle sizes.
Injection.... you can literally see... Visually indicated... On a gauge.... What your fuel is doing.
With a carb you could be bombing down a road and have your slide get stuck or a jet slightly block without even realising and completely alter your mixture and hot spot the piston.
Injection would either cut out before it did damage from irregular parameters or it would adjust those parameters to bring the mixture back to 14.0:1 or wherever it needs it to be 👀
@@MaNNeRz91 That's true. I do own carbureted and injected bikes. What I mean by simple, in this case, is everything can be worked on with hand tools. No computer needed. I would be the first to admit though that it's easier to map my Power Commanders than to rejet a carb... but I can do one of those things on a trail in the middle of a forest with just my tool kit, the other I can't.
@@thevoxofreason8468 that's a fair enough example mate but with tech getting smaller and smaller you now have the ability to do ECU stuff over Bluetooth with a module over your phone etc. I wouldn't want to carry a laptop around although I do in my car for mapping reasons but a phone would be ideal on the bike.
My bike is carb. I've worked on all sorts of carbs and engines including RC, classic cars and bikes. But I definitely prefer EFI for the reasons in my last comment. I know you can have a wideband sensor on a carb set up too which is super helpful but then an efi system would read that information and adjust accordingly whereas a carb you then have to adjust stuff yourself.
I mean efi you can go from say a #50 jet up to a #200 jet without changing the jet 👍
@@MaNNeRz91 For sure. I agree. EFI is certainly easier to adjust, but my point was just that carbs are simpler. I can make a carburetor out of a tin can...like Harley did on their first machine (although I think that story's apocryphal). Anyway, I'm just thinking worst case. In the mountains, bike stops running, no cell service, just my tool kit that I carry. I find out it's my carb or EFI that's the problem. I'd rather it be my carb.
@@thevoxofreason8468 to be fair if it's serviced well there shouldn't be any problems with the efi or carb. I think for mountain riding efi all day long though. If you're riding around a certain altitude then carb will do too. Personally I'm always adjusting my carb slightly depending on time of day. The dense air on the morning when I go to work at 5am allows me to run richer but when I finish work it will not run right until I lean it off slightly. Could definitely do with a efi system but I cba to retro fit one 😂😂
The tin carb thing is intriguing lol 🤔🤔
Absolutely love this video brother and how smart u are I have a 02 wr426 that was supposedly rebuilt it runs and drives absolutely amazing starts first kick most of the time then quite often it will sputter cut out run a lil choppy it dies a lot then after awhile it might start back first kick like nothing happened then might not I just wanna get it linked out a tuned up where I can rip with my dad if u could do me on something and possibly help I’m stayed away but I know how to work on stuff if u could give me ideas on what to check please and thank u keep up the great work and getting these bikes back out there fixed up for more people to enjoy 🔥🙏🏼
Awesome video man
Keep up the awesome content
To me when you pulled the rocker cover off the camshaft did not look like it had the lobes facing up like it should with correct timing. I would definitely be re checking the timing
Man that crank case leak sounded like a plane flying over head 😂😂👍🏼👍🏼❤️❤️
I had an xr350. Also a washer was missing at one cylinder bolt, which left me with no compression. The cylinder head then pulls skewed while tightening the cylinder head bolts.
My pilot jet fell out on my 450r and it would only run at WOT. Broke my arm that day 3rd gear pinned up a rocky hill climb. Def got some carb or valve issues if it doesn't start easily
I have not worked on this particular model, but I'm thinking the head gasket was a bit dodgy. I don't see the rings, jug, or piston being an issue. The decomp mechanism is definite possibility.
I had the same issue with mine. In my case is were the inlet valves. There were worn out, new ones in and it runs again
I can't help but notice, usually when you kick things over you crack the throttle a little. From my experience most bikes especially race bikes don't like that
Crazy deal, new one on me, got a bike in that has carbon fiber rods in it. Guy spent a ton on the build obviously. Wants OEM parts put back in, shouldnt be an issue. CBR 1000 rr. Lost compression, broken rod it looks like... yay. Great vid Joe.
Watching you drain fluids is oddly satisfying.
To me fuel injection and dirt bikes seems really silly. Too many electronics to possibly fail. And yeah, that spark plug.......pretty sure it goes through the bottom of the crankcase. Damn!
Injection requires less changing in regards to altitude and weather conditions which it does itself. Carb is more reliable at the conditions it'd tuned for providing nothing gets blocked or stuck.
Injection can be programmed to change spray amount and timing and will work more efficiently providing you keep the fuel sensors and injector clean
They run far better & are proven in racing an off rd riding! My 2 newer Yamaha sport quads are fuel injected..no probs!
@@MaNNeRz91 FI is proven & better by far now in '22.
Another great video!
I have a question I see you lube up the cylinder invites quite a bit with oil I was wonder what exact oil that was
First things first. I like your channel and just subscribed. I think u r a good mechanic.
I agree with your assessment. A tip from my experience - when someone tells me they did a valve adjustment, that's the FIRST thing I check because most folks don't make it perfect, but "good enough." And when I do valves I also do rings because I am there and rings are cheap.
I am not sure I wouldn't hone that cylinder too because why not?
Honda CRF awesome vintage you are great can sort any bikes out love your channel class👍💯🙂🇬🇧
Not that familiar with the crf250 but had a similar issue with a 2 stroke 125. The woodruff key on the magneto/crank had sheared off due to the bolt coming loose. It would backfire and kickback the kickstarter. Not that this is the issue, but is easy enough to check. And if the head gasket was bad enough to cause low compression then I'd suspect you'd have antifreeze in your oil.
Still pumping out great content 👌!!
Iv Ben watching ur videos for years now sence beginning u the man u can fix anything
I had a pretty new trx450er that the decomp stuck making a clicking noise. It still ran, looking forward to part 2
Had a YZ 450 with a key way problem on the crank.. Hard to remember the details, but a new keyway and it ran again. Easy enough to check..
Yo, I need help. I have a 1996 Suzuki rmx 250, and it has a PJ stock carb. Well I tired to fix it and I ended up breaking something on the inside l. So I ordered a 38mm pwk kehini carb and I can’t get it on
Love your vids dude my son has the 2020crf150r too get the spark plug out I use a piece of garden water hose works a treat can you give that a go and see how you like it
We need a video of a ltr450 that’s like the last one we haven’t seen you work on 😢
Any amount of wear on a gasket could cause a small Leak. Large leaks that build pressure in the lower end and cause damage would more then likely been a catastrophic failure like a crack. Your decompression chamber was probably adjusted after the leak first became present that's why it was adjusted, as you said the owner got it to fire once. I would clean all gaskets and re seal them with new adhesive. I had a Suzuki bandit that had all the same issues and it was a result of the gasket leaking into a oil chamber building pressure in the bottom without leaking in to coolant.
Very interesting! Glad you found the problem.
Since he adjusted the valves and she never ran since my idea is also the compression valve, or mechanism. Since those rings could have been put in a racing bike you would wish for no leakage but that is tilting at windmills. With new rings and different valve adjustment she will run and scare you good.
having the same issue right now on a project KLX Kawasaki 250 to 300cc conversion. the bike was stock up for about 15+ years. i changes the block and valves and machine shopped the head. my feet is swollen from the kicking. gaskets are new and the seals as well
Excellent videos!
Love ur vids
I feel like he like fixing more than riding hope he opens a shop one day. His subs would be there first day ready to get shit fixed
Hopefully in the near future! That would be awesome!
@@2vintage you got this man just keep up the hard work
I wish I had my TRX Honda foreman rubicon four-wheel drive quad running right now doesn't want to come out of gear any tips?
Hello! Last year I had a 2008 crf250r at my garage. After a full rebuild of the engine the bike would start first or second kick but then shut off as the revs went down. The problem was caused by the decompresion spring which was having too much tension, bent it a little and the bike run like a dream. I am suspecting that this bike is having the same issue and I suggest you to take off the mecanism and bend the spring so it does have enough tension just to move the decomp. weight back to the center of the cam. Mine would also make a ticking noise before shutting off every time. Good luck!
After a Full OEM rebuild, my does the same thing. When the revs start to fall back to idle, I here a little ticking noise but only for just a second and it shuts off. Can you give me a little more of an explanation? Take the mechanism off and bend the spring to make it harder to work? Make the spring tighter so it has more tension? Thanks!
Make the spring softer is the answer.
lov the vidsss
Every time Joe finds a problem he be like “that’s not good” 😂😂😂
I have a 1990 CR125R an when it start it it revs out high. Do u know what I can check to solve this?
Because it didn't had a washer under the other head bolt it could be that the cylinder head bolt bottom out when fully toque meaning you don't have the full torque on the head pushing on the head to seal the head gasket if it makes any sence. That can also be that head bolts could be stretched and loose compression on the head. Can be decompression work with central fuegal force and kicks the exhaust valve open slightly for a lower compression for easy starting and the best way to do another test on the head is to put spark plug back in and lay head flat and fill it up with water or oil/ brake fluid and see if you loose fluid , if so valves are leaking
how much stuff do you go and view but then walk away from
I have the same bike and the motor needs to be rebuilt and I don’t know how to 2vintage do you think you can do it for me
Probably a worn-out piston and rings. The pistons in these throwaway 4-stroke MX bikes are basically an aluminum wafer with 2 ring grooves and a tab on each side called a piston skirt. Titanium valves that stretch under high RPM also start leaking and cause low or no compression. Head gaskets can also fail, but not as common a problem as the wear-out parts.
theres separate gearcase oil? the oil on the dipstick was new but looked like shit when you pulled the plug off
With that low a compression reading it points to valves. I found take the valve springs off and check valves move freely.
if you have a decompression mecanism how y gonna have compression? since it is a injection bike u ahould always check if it is actually injecting fuel before tear down,,
When I put mine back together the timing chain tensioner as I tightened it up threw my timing off...still do not know what I did wrong...hopefully when you put it back together I will learn something.....
Your marks should be lined up when the chain is tight i always push the chain guide with my finger to double check that. It sounds like you may be a tooth off. Another thing ive seen is cam chain was stretched throwing the timing off
Can I use a dirt bike battery if so how do you use it bro I appreciate any info man thanks
Where did you download the service manuals?
I own a 2005 CRF250R, purchased used, it was in great shape, but was a nightmare to start, literally required a satanic ritual. I cleaned the carb, set the float height, installed JD jetting jet kit, checked valve clearances, replaced the spark plug, replaced main wire harness, drained old gas and replaced with new gas, tipped the bike over to drain any excess gas, (made sure it wasn’t flooded). After all that work, (done in bits at a time) the bike works like new, often starts on the first kick, sometimes takes another kick or two. I believe the main culprit for my bike was the main wire harness. It had been spliced in many spots. I went from hating that bike and regretting buying it, to loving my bike, and I’ve put quite a bit more money into it since then. 🙂 Maybe this will help someone else who is having starting issues…just some stuff to try or check.
Backfiring might mean spark taking place at wrong time when inlet valves are open. Similarly good compression requires cam timing to be correct with respect to crank and piston position. Is it possible crank/flywheel keyway has failed ?
I'm not sure why they don't take The bikes to a proper mechanical workshop centre
I know it's a bit expensive though, better get people who are more experiences working with the bikes
Hey man a I have a 2001 Kx 85. I have had it for about a year. I’m wondering how long until it will blow up? It’s got over 200 hours and has really high compression and runs very well. Any ideas?
Any time after 2-hundo..
Def confirm that plug is proper size & REPLACE!
Great find boss roll with it nothing to lose, but get a new piston and rings you got the head and cylinder off might as well do it anyway
Can u show how to step by step fix it because my bikes doing the exact same
Has the bike been set up for fmx freestyle ?
friend, nice vids🤩... I have had this issue lol, first time I ever noticed valve's Grow?... Valve seat's are to soft and the slamming of the valve eat's it?... lol Good luck
Honda Crf250s and 450s are notorious for getting too tight valve lash making them hard to start. its always recommended that on carbureted models to twist the throttle a good 4 or 5 trust to prime the engine before kicking over
Your theory sounds right to me brother. Be safe :)
Did you ever think to check the timeing chain to make sure cam and crank where timed right. Also check for stretch on the chain.
if there's stretch on the chain would it be a problem
I had that same problem on my scooter but in my case it did start and it was a 2 stroke any advice would be welcome
Its probably running lean. Check for an air leak or richen up the idle mixture.
My crf250r 2011 had the same problem and it was the TPS on the throttlebody that was broken.
My 05 crf250x supermoto just locked up few weeks ago im about to halfto go through all this same stuff
ah bummer! I hope you get it fixed up!
i had the same problem on an 07 crf 250r wounld start and it was a broken spring on the decompression
I feel like it's the head gasket or I think the valves aren't seated properly. I know you did a leak down test but I'd pour some gas in the intake port and exhaust port and see if any gas leaks out the valves
Heck yeah brother when my bike get paid off I was looking at a 250 nah im getting an atv fast one too
Might be decompression problem so the valve stays open a small bit and that's why it back fire throughout the exhaust and valve
Great video
where are you out of man? i have a kawasaki that i cant get started and ive been trying for a few weeks now and truly could use some help. ive got fuel going to carbs and spark and good compression but no start. my stator wires were fried and melted which fried the stator, so i bought a new stator and wires it in and still no dice. im completely stumped
1990 kawasaki ninja 600d
I have a 2006 trx 450er ran yesterday does not start hmu if you want to make a video of trying to get it running
Why are you saying that the compression is low? So what was the issue?
You need to do 80psi for the leak down test. 20psi isn’t enough.
Check the reed valves.& seals., the decompression relief valve. Know as pop off pressurerelief valve. It most likely is. Those intake valve has to be set at .005 to dead on. It would not be labeled in the book if you could leave at .006 theit .001.& yes there is A bigger clearence in the intake valves to now.
yeeeeaaauuupppp gotta check that damn fly wheel, bought a klx140 2 wweeks ago im an expert on this kinda stuff
Surely a single piston ring with any sort of end gap will leak?
My yx 140 pitbike was doing that and it turned out to be the inlet valve was Bent
very first thing you should have done is spray it with ether and see if it would light up. I've built countless honda unicam motors and that one looks healthy enough to run. check fuel pressure. should be around 50 psi
Maybe the compression tester wasn’t fully seated? 10 psi u could push the kick start down with your pinky!! And a very little leak through the rings is normal they never 100% sealed
23:25 It looks like the exhaust valve was contacting the piston. See how one valve relief is black and has soot. The other valve relief has the perfect circle of the valve in it. Almost like it was contacting at some point. I would definitely make sure the piston is not cracked and that the exhaust valves are sealing. Pour some rubbing alcohol on the top of them and make sure it doesn't leak through.
I'd put money on the sprocket has spun on the cam.. have seen it a couple times
Well while you have the head off take the valves out and clean them and measure them to see if they are in spec and the valve stems are OK as well , if they are all OK I would say it uas other issues but can diagnose over a video but look for black tracking on the head and cylinder as this will show where the gasses were going if the head gasket had blown
check valves , re do the timing ( guess its off ) if the valves seat all the way( so you dont have leaks ) and it gets gas and timing is 100% right ( check spark ) then it should run
Timing off most likely g .. it’s firing but most likely off time .. make sure it’s not off by a tooth .. check compression and make sure the bike is holding at least 100 psi if not then see if the valves are out of spec ( seats needs to be recut if the valves aren’t sealing then the shims need to be replaced ) ….
Youare my favorite dirtbike and motorcycle mechanic
Some years of CRF's are also known for having hard valve seats and soft valves that end up stretching. The valve stretch causes air leaks and will eventually collide with the piston and cause catastrophic top end damage. Not sure if this one falls into those models I'm not a newer 4 stroke guy.
Totally agree....Those early CRF250's were notorious for this. No or hard to start and backfiring were sure symptoms of valve/valve seat issues..
I have to wonder if the decompression mechanism dumps compression till the bike starts then a compression test would only tell you what it leaves in their not its real compression I think your rite and it's dumping off to much
Is this the worlds first Honda that don’t start. I’m impressed
My warrior bent its second set of rods from the compression mechanism spring failing
That's got "Someone's been here before " all over it . washer missing from the head bolt? were they even torqued down ? Didn't see you remove them in the vid ,20 psi is not a lot to use on a ldt thats why you could barely hear it comming out the crankcase.
Joe, if the compression is going out to the crankcase, I think it is not because of the decompression system. My bet it is because the headgasket was blown on the timing chain side.
Thats what I was thinking too. Interesting video.
exactly my first thought
Yup. I'm sure if he'd bumped the air pressure up to something like 40 psi it would have really made a difference on the leak down test n prolly even would have started leaking air into the coolant too
what gasket mate im not sure can you explain further thanks
@@benmiller5015 maybe the gasket is blown but not on the coolant passages, instead on the timing chain sid and this is why it leaks to the crankcase, this is my theory