gx31 honda 'sometimes' looses power

[alexander]

Hi folk, Alex from New Zealand here.
I've got a problem with a honda gx31 engine that sometimes, especially when warm, looses power, sometimes to the point of just about having 'stuff all' left.
But even when warm, sometimes it suddenly runs with full power again.
That POWERLOSS goes together with a repeating "SWALLOWING SOUND", that sounds like the motor is not getting enough fuel or not enough air.
Its not the sound that usually goes with a bad spark ('missing').
It did that many times before, but usually settled back into running with full power again (even when hot) but now it happens more often.
(The motor has never been overheated).
Its not the airfilter.
Its not the breather in the fuel cap.
I took the carburator apart, cleaned it twice.
I checked the sparkplug clearance and condition (i will next get a new plug to eliminate that possibility, just to be sure).
I even checked the valve clearance.
Could it be the MEMBRANE in the carburator?
I looked at the MEMBRANE and the STEELDISK on it when it moves 'in and out' does so at an slight angle, not totally flat, which makes me think that it might sometimes open at that 'angle' (not getting the right amount of fuel/powerloss) and then suddenly go 'flat' (right amount of fuel).
I will next order a new membrane (if i can still get one seperate).
I also will try to run it without a FUEL FILTER in the tank just to see if the filter might be too dirty because the motor has done over 10000km/300 hours.
That filter in the tank can't be cleaned because it is dense felt and has another superfine filter behind it, so after 300 hours i think it has done it's 'dash'. I will do that and get back to you regarding that.
But i might be wrong with the fuel/air being the cause.
Could it be the COIL or the distance of the MAGNETO to the coil .
I moved that ones but hardly think that would cause such a problem, but i might be wrong, now that i say it out loud, i should realy change the distance and try again; .... does anybody know what distance the magneto should be from the coil; i adjusted it with minimal distance).
I thought somebody might have had a similar problem and was able to solve it and can save me from 'sleepless' nights.
Thanks a lot for your help. AL.

 

[Mountainman]

thinking it's the membrane or ?? something gas related
one cool thing about Honda
they are easy to get hold of on the phone or e-mail
they answer all questions and who knows better than them
exactly what goes wrong with most
most gas filters located in tanks can be blown out for cleanning
MM

 

[fetor56]

Can't help u much Alex cos i've got a GX35 & their different engines...i've never had trouble with mine but it hasn't done nearly the K's/hrs as yours.
You had a valid point about the fuel filter in the tank...at some stage it must reach the end of it's usefull life & thereafter start giving trouble.
How do u mean u moved the coil in relation to the magneto...moved it how(removed & replaced)?
I agree that it shouldn't make a noticeable difference(unless their way too far apart)
The diaphram in the carb is also a known weakness(particularly over time) & different fuel additives(eg,ethanol) don't help.

 

[Esteban]

Are you using good, fresh gas in it ? I don't use any gas that is over a few months old.

 

[Old Bob]

Per Honda service manual:

Spark plug gap .024"-.026"

Magneto air gap at flywheel .014"-.020"

Clunk could be clogged with that many hours. If the power drops off and comes back thats a good sign the fuel flow is restricted.

The metering diaphragm should be limp and no wrinkles.The pump diaphragm should also be limp and not stretched tight. You can get metering diaphragms seperate.
(see attachment)

 

[alexander]

honda gx 31

thinking it's the membrane or ?? something gas related
one cool thing about Honda
they are easy to get hold of on the phone or e-mail
they answer all questions and who knows better than them
exactly what goes wrong with most
most gas filters located in tanks can be blown out for cleanning
MM

Cheers mate, good idea, do you ring/e-mail honda in the usa or do they have a 'world
0800 number'/e-mail, if the later, you wouln'd have the number handy? Thanks again, AL.

 

[Mountainman]

alexander our motor biking friend

Cheers mate, good idea, do you ring/e-mail honda in the usa or do they have a 'world
0800 number'/e-mail, if the later, you wouln'd have the number handy? Thanks again, AL.

you may wish to try this web site ??

www.perr.com/honda.html

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

 

[alexander]

honda gx 31

Can't help u much Alex cos i've got a GX35 & their different engines...i've never had trouble with mine but it hasn't done nearly the K's/hrs as yours.
You had a valid point about the fuel filter in the tank...at some stage it must reach the end of it's usefull life & thereafter start giving trouble.
How do u mean u moved the coil in relation to the magneto...moved it how(removed & replaced)?
I agree that it shouldn't make a noticeable difference(unless their way too far apart)
The diaphram in the carb is also a known weakness(particularly over time) & different fuel additives(eg,ethanol) don't help.

Hi mate, thanks for your reply, yeah eliminating the fuel filter issue should be easy: just using it without one should show if that is the problem.
About the magneto/coil distance: I took the coil off without checking what the original distance was and put it back according to 'common sense' but as you see from the post below there is a definite distance tolerance that it should be within to function properly. Good to know, ehy.
And that diaphram is a worry, i never liked diaghram carbys, even on my BMW. I should have a new one as a spare anyway to be able to replace when needed and to be able to use to eliminate the diaphram as a problem when something fuel/air related goes wrong....
The fuel here in NZ is sh.t and that doesn't help at all, and some petrol station fuels here are better than others....
'By the way', what is the different of the gx31 engine compared to gx35?
And i totally agree with the weight issue and the ability to lift the bike over a gate, cause lots good tracks here have access trough locked gates and some bush tracks have trees fallen across them.
On one 6 hour trip i had to lift the bike over logs so often that my arm hurt for days/weeks after....
Thanks again. AL.

 

[alexander]

Gas! good gas? no good gas!

Are you using good, fresh gas in it ? I don't use any gas that is over a few months old.

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.

 

[alexander]

honda gx 31

Per Honda service manual:

Spark plug gap .024"-.026"

Magneto air gap at flywheel .014"-.020"

Clunk could be clogged with that many hours. If the power drops off and comes back thats a good sign the fuel flow is restricted.

The metering diaphragm should be limp and no wrinkles.The pump diaphragm should also be limp and not stretched tight. You can get metering diaphragms seperate.
(see attachment)

Thanks for that imortant information mate, a honda service manual would come in very handy, did you have to bye one or could you find one for free on the internet or from mates on the 'outernet' (and i will look on this forum to see if there is one somewhere....)?
But your info should keep me going for now, especially since i am sure now that i should have a spare metering diaphram (and pump diaphram) anyway to replace when needed and to be able to use to help eliminate that as a potential problem.
Your picture of the metering diaphram makes me also think that i can't remember that gasket that goes on top of the diaphram. Did i perhaps loose that when i pulled the carby apart the first time quite a wee while back, and didn't notice.... ('even monkey's fall out of trees' ha).
That certainly could/would be the cause of 'the hard to find problem' with the fuel/air 'powerloss on/off'.... and an easy fix.
Good on you, thanks for your help. Al.