Honda umk-431 brushcutter repair
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- Опубликовано: 16 апр 2019
- Here I try to repair my Honda UMK-431 brushcutter. I bought this brushcutter a while back and had planned to actually swap the complete engine with a spare GX-31 engine from a tiller that I have. Yet I feel tempted to instead repair the original engine.
I replaced the piston and pistonrings and I honed the cylinder in an earlier repair. Yet I still experience low compression and even have over-pressure in the crankcase. So lets open up and grind the valveseating and see if this improves compression.
You will allso see mee apply liquid gasket and do a valve timing adjustment. let's see if it will run better.
Please help me by giving feedback/commenting regarding the repair but also regarding the video, any suggestion is welcome.
off course are you welcome to subscribe! I plan to add more video's on all sorts of DIY projects! 
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The best video on a small strimmer engine well detailed help me a lot many THANKS
Thank you for your feedback!
very good job man !!
I like the paper trick for the gasket application 👍🏼 I usually use the corner of a small plastic bag and cut a small hole in the end . Check your piston ring gaps are correctly placed 👍🏼
Thanks for your comment!
Чётко .Без лишней болтовни и всё понятно .
Great work sir.
Thank you sir!
good work sir
I think mine i hv to change those valve guides! I was shocked to see no valve seals thr in my gx31. Nice video. I watched yyour video just to confirm GX31 do not comes with valve seals.. Nice video mate... Hope you soon figured out ur issue..
Thanks for watching and your comment!
We've got the same problem.. It's an engine blowby.. There's a combustion leak somewhere in the piston and liner or in a valve stem. Crack in a liner and piston will show up when it is heated and pressured.
fantastic job
Triangle mark on cam gear pointing down for top dead centre?
Loved your rebuild video. I just wish you had not used fast motion on the reassembly. Thanks for the GX31 breakdown and assembly.
Hello! Thank you for watching and your feedback, I will consider an new assembly video of the gx31!
@@tmdrtn thank you. Much appreciated.
Its good tutorial.
He is professional
Look forward to part 2 on this. I have a Husqvarna 224L with basically has a Honda GX25 in it. Thanks for sharing Best Wishes & Blessings. Keith Noneya
Hello, Thank you for your comment, I will make a follow up but have had little time and having trouble sourcing the correct piston rings.
I have the gx25 as well as a spare. I swapped rings on that one long time ago, food engine, has an overhead cam. Best regards
@@tmdrtn Got to thinking about it, if the GX35 has a larger bore, try using those rings and cut them down so the gap is a little tighter. Here's a link I found to some good info. You may have to use your browser to translate the page, but the manuals after download are in English. rentamaxcr.com/content/9-soporte-tecnico Just in case you may need it, I'm uploading a video right now on how to change the rocker arms on the GX25/35 on my channel. Best Wishes & Blessings. Keith Noneya
Excellent video!! It did look like you used the same valve clearance for intake and outtake. What clearances did you use if not the recommended .012 intake, .015 outtake?
Thank you, I did, this because I do not have the correct feeler gauges, I had to use the closest metric alternative, this also because I do feel this is not affecting my problem solving work. I have broken down the engine again and understand more about the most likely root cause, working on that video right now, will release soon!
Thanks sar
Sir gd evening mayron ba kayo gear head kasama inner rod
OK I will throw in my two cents. You said you honed the cylinder. After honing did you pull the compression rings into the cylinder and check end gap? If the gap is too large either the rings are wrong or you over honed the cylinder. Also what grit did you use for the cylinder honing? If the grit is too large the engine will smoke and have blow by until the rings wear the cylinder smoother. Rings. Even if they have the proper end gap they must be installed correctly or they will pass oil from the cylinder walls up into the combustion chamber. Since you are indicating oil being blown into the crankcase breather it is most likely a piston ring bypass issue. These engines are designed to run in all positions so it is possible you are sucking oil past the intake valve guide into the combustion chamber causing the blue smoke. If the head has removable valve guides that might address that issue. Most likely Honda doesn't replace them just offers replacement heads. My next statement is going to sound a little silly, but are you sure you are using standard gas not oil/gas mixture? Sorry for asking as you seem more than competent as a mechanic.
Thanks for your very elaborate response to my video. The honing might cause the issue, but since I used a very fine grid on a caliper honing set I do not suspect over honing, I measured the ring gap in the proper way and the gap is way to big, I'm having a hard time finding reasonable priced better quality rings to solve the issue, for about 10 years ago I swapped rings on a gx25 which back then I could pick up at the local hardware store, those times are long gone unfortunately. And yes, I'm using straight gas and actually always use aspen 4 on all my four stroke equipment.
Been having a problem with low compression, and am sure to try check the valves now. Thanks. Had not thought of that...
Btw, what's that gel you applied before grinding the pistons? And is there an alternative?
I using valve grinding past for the valves, am not aware of an alternative, best regards!
Donde puedo encontrar piezas para este tipo de motor. Honda C31.4
Bravo
Great video! Would a 4 inch diameter puller be large enough to remove the flywheel?
Thanks! Yes that would work probably! Good luck!
good
Hello thanks for the video, I had the following question; how did you position the piston with crankshaft relative to the gear that drives the valves. best regards
Hello and thank you for watching! I put the piston in TDC to dead center and positioned the cam gear in a neutral position so that both valves are in the closed position.
@@tmdrtn nice, thanks.
On the timing gear, look for one special tooth... Theres one dent/cut/slot... Position it on top...Then on the magneto fins theres one special fin which has a cut... Allign tht to one small nipple on the body of engine. Once both is checked, slowly lowered your piston.
I had problem with honda umk 435 t when acelarat raises there is a sound in engine
Great video really helped me , but what sealer did you used for the gasket, the red stuff? thanks
Thank you! The red sealer is a liquid gasket, available in many different variants and colors.
@@tmdrtn Thanks buddy:)
Hello thanks for the video,
So am currently fixing a parazzini engine, and its smoking really bad,
Also at one point oil came out of the exhaust. What could it be.
Hello, thanks for watching and your. Comment, I don't know that type of engine, hard for me to give any recommendations on how to solve the problem, but learning to understand how your engine works will help you to sort out any issue! Good luck with that!
I think it s better dont brush with rotate still brush the crankase brather. Good job !
👍
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Hi. Please advise what is better to get, Honda UMK 435 or Makita EM4351UH?
Hej, I am not familiar with the makita, but assuming it is a 4 stroke the difference probably is little. I would choose the Honda if the price difference is limited. The technology and quality probably are the same.
did you adjust both valves without moving the flywheel the second time
Yes, I did, do you think this could affect the outcome?
Yo repare 1 de las mismas y prendió todo bien pero el único problema esq no me sube aceite para los balancines no se qué hacer eh revisado y todo bien
Oil coming from the crankcase breather is a sign of blowby at the piston. Thus either your rings do not seal properly, or your rings do not seal properly. Thats from a worn bore, or shitty/worn rings usually. Shitty rings can be either assembled in the wrong way (e.g. top down) or the ring gap is too large, or the preload of the rings is too low. If it does not burn lots of oil (blue smoke) it is a problem of the compression rings only.
That is correct! The rings I mounted have a way to big ring gap, note that 1 millimeter. That is what is causing oil consumption, that rings where provided with the. Chinese piston kit I bought, will have to source original ones to solve the issue!
@@tmdrtn You might get away sourcing another chinese piston kit or an oversize chinese piston kit whilst only using the rings. This will total in a bit more tension on the bore, thus a bit of power loss due to friction, but you should have a bit more room to gap them properly if you're putting them into a bore, say, 1/4th of a millimeter too small.
Thank you very much of repair tips! Can you please show too throttle control (handle) parts constitution?
Thanks for watching! The throttle has various handle designs, which one do you have?
@@tmdrtn Thanks for fast react! Same type, which you have, mine go broken and not sure, how to assemble it :)
Aha, okaj, understand, I will see what I can do..
@@tmdrtn Thank you so so much in advance! And too these very helpful videos ❤️
The horrible clattering sound is your first warning sign that something isn't right.
Qual seria a folga de válvulas ideal
Me quiero comprar una honda 450 es buena ??? Se compara con la Stihl 450 ??? Digannn cual compro ????
habe auch eine umk 431 motorsense. bei vollgas geht der motor aus. Zündspule defekt?
Hello! Thanks for watching, I don't think the coil should be the issue since it is a fixed timing, most likely dirt in carburetor, at full throttle the engine is probably not getting sufficient fuel flow, please rebuild or swap the carburetor!
Hi. I'm using the same trimmer, I noticed the airfilter is full engine oil and spitting engine oil from muffler. And it's hard to start. Can you me help pls.
Hej, start by checking oil level to high, otherwise it looks like similar problem as I have where the wear and gap of the piston rings and piston need to be checked, other possibility is that the valve guides are worn causing oil consumption, best to disassemble the engine and check/measure if your within tolerances. Good luck!
hello sir. i have problem with machine won't start . i dont know what is the main problem at all . any suggestions... please share !
First check if you have spark! Second check if you have compression, third check if youbhave fuel in combustion chamber. Use starter gas to test engine or pour a few drops of fuel through the plug hole.
Why dont you show the filler gauge clearance
Can you help me with the name of two pins which you took out at 11:00-11:04min of the video.
Hello! These are the pushrods!
Sir overheat ho rahi h white
TDC before setting the valve clearance?
Yes, that is correct
Kuya my piyesa b kyo yan
Hi sir valve gap and coil gap clearance?
Google honda gx31 enginespecs and you'll find it!
Iske parts nahi milte hai
5:00 what tool did you use to remove that part?
Hello! I used a universal puller to remove the flywheel.
Here is a link, I have the 3 armed version; www.biltema.se/bil---mc/bilverktyg/avdragare/avdragare-2000019462
@@tmdrtn Thank you very much!
Thank you.
Where are you from?
Thank you for watching, I in Sweden
Great~
I enjoyed the video
I'm korean.
Hi, have you considered the oil outlet valve in the bottom of the crankcase. It’s meant to stop oil draining into carburettor but still relieve crankcase pressure.
Hello Pete, thank you for watching and for your comment! A good one as well. I have not really considered it but believe to have assembled it correctly. Can this 'wear out you think? Best regards!
👍👍👍👍👍
Thank you!
How do you lubricate the honda brushcutter head
Yes, there is a grease nipple on the brush cutter head! Otherwise you could open it up and pack it with grease manually
do I understand correctly-- oil pushed to carb because of leaking valves? anyway, love you work.
Hej, thanks for your response, the crankcase vent is connected by a hose to the airfilterhousing, carb then sucks in oil, causing smoke!
@@tmdrtn that part i understand, have the same engine, never used, bought it on ebay, it pumped half of oil out of that tube even before I started. So my ? is-did that was fixed after You done with repair. Thanks.
@@alexbilenkin3418 Hello again, no it did not solve my problem, only partially, I did change pistons and rings earlier, it could be that I have mounted the rings in the wrong way, or that I have honed the. Cylinder to much, that I have yet to check, have been too busy with the Seat Altea XL.
@@tmdrtn You did replaced horn, what the problem now? If for some reason I don't return GX31 and fix it, I'll update You.
@@alexbilenkin3418 nothing special on the Seat but routine maintenance, fix that Honda! I will make follow up video by popular demand!
Kiya reason h
can you make a video about the carburetor please?
That is a Good suggestions, would you like to see taking apart, cleaning and assembly?
@@tmdrtn yeah, that will be great. and please also how to diagnosis carburetor problem video. thanks!
First, get the measurement of the compression that you're getting.
For the low compression, it is either the rings or the valves that are not sealed properly.
For the rings, you have to assemble it correctly. Make sure the rings are facing the correct position to get good compression.
For the valves, have you do a leak test. The valves need to be sealed tight as well.
Please get the genuine rings from Honda.
Hello, Size of oilseal for 4stroke
What?
Hahahaha
Hi my friend where I can buy a genuine GX25cc and Gx35 Honda's
Hard to tell, depends on your location, Google them
Connecticut state
I sorry my friend Im not in the states, greetings from Sweden!
Sounds like garbage after rebuild. Why?
Agree! The heatshield of the exhaust is loose, therfore vibrating! Best regards!
Medida en mm la luz de valvulas?
Hello! I do not know, but I'm sure you could find the answer to that question online!
@@tmdrtn Umk435 honda luz de valvulas?
Supar
oil push to carb becaus of bad piston ring replace piston ring
That is correct, the chinese rings I used here have to big gap causing blow by and oil consumption! Thanks for watching
वायर खींचने वालाकैसे लगाएं
O singură greșeală ! Siliconul nu se curăță la peria abrazivă, deoarece se strica fata de etanșare a piesei, salvarea este siliconul dar nu este corect.
Thank you for your reply! I am not really worried about damaging the mating surface of the castings since I re-apply silicone gasket again making a sufficient seal! Thank you for watching and your concern!
should of cleaned all the carbon shit off the valve before even attempting to use the valve grinding paste. can then see is the valve stem has any deformaties..... and actually would put new valves in anyway.. and only use those valves for grinding in process.
You need to talk to tell me what you’re doing
Es machine ke har parts ke nam par video banaye sir please
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Hindi me only hind
Abe samjhana nahi to dikha Kyo rha ha