Honda GX 31 problems

Discussion in '4-Stroke Engines' started by Fred Fry, Sep 14, 2010.

  1. Fred Fry

    Fred Fry New Member

    My Honda GX 31 doesn't want to run at full throttle.
    It seems that at about 3/4 throttle it starts to die.
    If I try to give it full throttle it bogs down bad and wants to die immediately.
    If I back off the throttle when it is starting to die it runs good.
    I cleaned the air and fuel filters, and it ran better for awhile, but not long.
    Can the fuel filter look clean and still be dirty?
    I guess I could try to run it with no filter and see if that makes a difference.
    Well Fellas... I am asking for tips as to what this problem could be.
    My next step to fixing the problem is to take the carb apart and look for wear.
    Any help will be greatly appreciated.

    PS> This motor sat for 2 years and when I parked it ran great.
    Did sitting that long with old gas gum up the carb?

    Thank You, Fred
    Last edited: Sep 14, 2010

  2. Dieing

    Hi, where do you live? CA gas causes this, at least in my Honda.

  3. HoughMade

    HoughMade Guest

    I still think it's fuel starved....and yes, it can look clean and be dirty. My question is what kind of filter? If a screen filter, I have found they can let enough stuff through to clog a carb. If a paper filter, it can restrict while looking pretty good.
  4. Silvaire

    Silvaire Member


    It is almost a certainty that you have a fuel system problem.

    These engines use a Walbro WYL series diaphragm carburetor. Among its various systems is a one way flapper valve in the fuel pump section. With the fuel we have to use nowadays (and especially if it has alcohol in it), this flapper valve curls and stiffens after awhile. At high throttle settings the pump can no longer keep up with the needed fuel flow and the engine cuts out due to fuel starvation.

    The solution is to disassemble and clean the carb and put it back together with a new carb kit. Most likely the gasket/diaphragm kit is all you need and not a full carb kit. The gasket/diaphragm kit is a Walbro D11-WYL ($4.49), and the full carb repair kit is a Walbro K20-WYL ($8.29). My source for these (at these prices) is Their shipping cost is low and you can also get fuel line and primer bulbs from them too if you need them. (These carb kits are generally stocked by better local small engine shops too, but usually for much higher prices.)

    This is QUITE LIKELY your issue, but there are other fuel related possibilities. Check that your fuel lines do not have any cracks or kinks in them and are still reasonably soft, and that fuel flows freely out of the supply line when it is held below the fuel level in the tank. Check especially for cracks where the fuel line attaches to the filter. You probably don't need a new filter/clunk though. I would blow back through it with compressed air a few times to clean it though, soaking it in fuel each time to rinse it out as you do.

    Hope this helps...
    Last edited: Sep 14, 2010
  5. Old Bob

    Old Bob Member

    silvaire hit the nail on the head, replace the diaphragms.
  6. Fred Fry

    Fred Fry New Member

    Thanks so much for the info guys.
    I ordered the diaphgrahm yesterday.
  7. boyntonstu

    boyntonstu Member

    Same thing happened to my GX-31.

    I bought what I thought was a new carb on eBay.

    It came in a plastic bag and it smelled like gas when I opened it.

    I don't believe that carb makers run gas through them, do they?

    The same bog happened.

    However, and this I find interesting, by running it with the choke about 2/3 closed, it runs strong.

    Perhaps it is gulping gas, but it is running OK.

    Comments welcome.
  8. darwin

    darwin Well-Known Member

  9. boyntonstu

    boyntonstu Member

    I bought one on eBay.

    Unlike the OEM carb, the aftermarket one has a brass screw adjust located just above the fuel inlet tubing.

    It has an effect but I need to play with it some more to see if my bike will hit 29 mph like the engine did in the past.

    So far 21 mph. Not too shabby on my tiny bike because it feels like 40.

    Did your carb have the screw?
  10. darwin

    darwin Well-Known Member

    Yes it did, I like having that option to fine tune it.
  11. boyntonstu

    boyntonstu Member

    Great! How fast did it go?
  12. Jack gx31

    Jack gx31 New Member

    I have fuel come up my return line and it would only run half throttle with choke in and out then i got it to run off the main line and it would only get a little more
    Can anyone help
  13. Old Bob

    Old Bob Member

    Clogged tank vent, clogged air cleaner,plugged fuel filter or clunk,dirt in fuel passages,bad pump diaphragm,
  14. Jack gx31

    Jack gx31 New Member

    Narr none of those are the problem ive pulled the carby apart heaps of times and defently know they arnt thenproblem
  15. Old Bob

    Old Bob Member

    Did you clean the inlet screen? Is the return line above the fuel level? Do the pulse holes line up correctly, are the carb screws tight?High needle set correctly?Metering lever set correctly? Metering diaphragm old?