gx31 honda 'sometimes' looses power

yeah man....

you may wish to try this web site ??

www.perr.com/honda.html

have a good day wished for you -- from -- Mountainman

Good site you gave me there, will keep me going for a while....got lots to check now, not the least looking for that mysterious gasket that goes with the metering membrane that i MIGHT have lost when i pulled the carby apart the first time long ago ('even monkey's fall out of trees'), that would be an 'easy fix' ....will need to check later....busy busy....hopefully less 'sleepless' nights to look forward to....
Thanks again, have fun.... Al.
 
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Check your head gasket. I broke my gasket for my mitsu 49cc and it made that sound, and had near 0 power. It could be a loss of compression - i didnt read that you tested for it?
 
headgasketitsnot.....

Check your head gasket. I broke my gasket for my mitsu 49cc and it made that sound, and had near 0 power. It could be a loss of compression - i didnt read that you tested for it?

Thanks mate, one should consider all possibilities....one of the good things about the gx 31 etc. is that it is 'forced air cooled' and doesn't depend on the air flowing past it trough the 'forward speed' like so many other motor bikes, cause that means even if you are going slow, like going uphill in 'summer', or stop/start in town (in summer).... it still gets enough cooling....
my old (1970) bmw (motorbike) use to get so hot at times that i had to put an oil thermometer on it to make sure it wasn't getting too hot at times....
I (gx31) go from sealevel to 400meters twice weekly and to over 800meters once every 2 weeks (with a 3 speed gearbox/hub) and i was worried the first time i did it in middle of summer in the middle of the day...., but the 'baby' just does it, again and again.
i bet many normal 'aircooled' small motors would have given up long time ago....
i have a compression tester and after 10000km wanted to know anyway what the compression is like and how much the motor is worn because the BIG QUESTION for me is still out there to be answered: how long does a 4stroke 30ccm motor last in a 'motored bike', especially when it gets the workout i give it.
it needs to last at least 20000km otherwise i (and others) would have to replace it every year (no good). sofarsogood: no significant oil usage, no 'metal' ever in old oil, no obvious wear/pitting on visible valvegear, even the valve clearance is still within its tolerance etc. (having used only fully syntetic oil).
BUT, you just never know...., even without a compression tester one could check a (cold) motor/headgasket with soapy water around the headgasket and look for bubbles forming....
But, "you just never know" (did i say that before)....ones in middle of winter (long long time ago) my bmw crapped out, wouln't start and my mates and me spend the next hour or two (three) pulling the bike's electrics to pieces....and you know what it was....i (or somebody else) leaning on the bike had moved the (then usual) handlebar mounted (small and hardly used) 'killswitch' accidentally onto its off position....
or the time dirt got IN BETWEEN the 'points' (no electronic ignition) and you look for everything else but THAT easy (but not likely) one....
e.g.: a good way to look for (some) 'spark problems' (especially if it happens in rain) is to look at the coil/cable/magneto/sparkplugcap etc. in the DARK, then, any 'shortening' will be clearly visible....
Hence asking MY MATES on this excellent forum...., because no matter how much you know or how many miles you have done on two wheels, THEY can give you just THE HELP you need, when you need it....
(and i hope to be able to return it one day....)
Thanks a lot everybody.... Have Fun.... AL.
 
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Sorry mate, no good gas where i am....but some is better than others....i think it would make a difference for sure but not as drastic a difference as what it is.
But very good point.
Cheers, AL.

Name brand gas and, since they changed to 10% ethanol here, 89 octane gas DO make a difference...namely the Shell's and Amoco's have a consistency, while the discount types are mixed on site. (Too much water content would create a vapor lock effect.)

I've noticed the difference right away when my old 87 octane started my engine a coughing, and talked to 3 chainsaw repair shops.

Name brand blends and 89 octane is the recommendation they all gave me, it's what the professional loggers are doing nowadays. If your filters are good, that would take care of the "fuel" part of the equation.
 
I like some of the older engines & as Bama said above, " There is a difference in gas." The old Ohlsson & Rice, Bike Bug types, & my K & S do not like cheap 87 octane. I use at least 89, & put in some " stabilzer ", that I also use for my boat engine. Runs better, & keeps the tiny carbs from getting clogged ! KEEP these little motors clean internally !!
 
Check your head gasket. I broke my gasket for my mitsu 49cc and it made that sound, and had near 0 power. It could be a loss of compression - i didnt read that you tested for it?


There is no head gasket on the Honda mini four strokes, the use one piece cylinder and head casting.

Checking compression on a the mini four strokes won't tell you a thing with the compression release in place.It will always read like the engine is shot, thats how I bought a used GX31 for $17.50 shipped, the owner was told by an engine shop that the compression was low and the engine was shot.

But you can perform a leak down test. A leak down test is better test of the cylinder condition anyway.
 
Check to make sure that there's not something partially blocking the exhaust - these motors often have an anti-spark screen on the output of the muffler. Remove the two screws that hold the short chunk of exhaust pipe on the muffler output

If you have loose piece of rust (for instance) that is periodically getting blown into (and blocking) the screen, it could cause your symptoms.
 
Name brand gas and, since they changed to 10% ethanol here, 89 octane gas DO make a difference...namely the Shell's and Amoco's have a consistency, while the discount types are mixed on site. (Too much water content would create a vapor lock effect.)

I've noticed the difference right away when my old 87 octane started my engine a coughing, and talked to 3 chainsaw repair shops.

Name brand blends and 89 octane is the recommendation they all gave me, it's what the professional loggers are doing nowadays. If your filters are good, that would take care of the "fuel" part of the equation.

Thanks for that, good info....with the fuelusage we have the price of fuel doen't make a difference so might as well use the best.
Cheers, AL.
 
"Leak Down Test"

There is no head gasket on the Honda mini four strokes, the use one piece cylinder and head casting.

Checking compression on a the mini four strokes won't tell you a thing with the compression release in place.It will always read like the engine is shot, thats how I bought a used GX31 for $17.50 shipped, the owner was told by an engine shop that the compression was low and the engine was shot.

But you can perform a leak down test. A leak down test is better test of the cylinder condition anyway.

Cheers Bob, interesting to hear what you say about compression tests....i was wondering anyway because without being able to run the motor at a certain amount of revs (specified for compression test in service manual at 1200rpm) how can one do a C.test anyway.
But what you say about a 'leak down test' sounds good.
That sounds like 'seeing how much liquid' gets past the rings and cylinder....
but could you perhaps explain more about that test and how it is done and how to evaluate the result. Cheers, AL.
 
Check to make sure that there's not something partially blocking the exhaust - these motors often have an anti-spark screen on the output of the muffler. Remove the two screws that hold the short chunk of exhaust pipe on the muffler output

If you have loose piece of rust (for instance) that is periodically getting blown into (and blocking) the screen, it could cause your symptoms.

No sreen/spark arrester etc. on my 'baby', but now that you talk about the exhaust it does make me think....cause i do have a rattle in/on the exhaust that i thought came from the exhaust cover and backing plate behind the exhaust....should try running it without exhaust (or just without cover and plate to see where the rattle really comes from) just to see....but i need to run it for a distance....would bring some memories back from my 2 stroke days terrorising the neighbourhood with loud exhausts....have to dig my rad sunnies out for that one....need to make a custom exhaust anyway for my mark2 model, so now might be the time....
Cheers for that info, AL.
 
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