HONDA GXH50 cuting out after 10secs

Discussion in '4-Stroke Engines' started by Atudge, Feb 2, 2010.

  1. Atudge

    Atudge New Member

    Honda gxh50

    Okidoke so Ive got a gxh50 and its in great condition the carb is clean as a whistle as is the cylinder,fuel and sparkplug as you would expect for a pretty much new and unused motor

    However upon starting the motor is runs for approx 5-15 seconds at idle speed only with choke on and max fuel before cutting out wont let me rev it without cutting out either.Now as theres a spark fuel and air I really cant seem to suus out what the score is with it.Ive tried checking the oil level thats fine and also disconnecting the oil sensor which can cause issues..still no joy.

    So I have put it down to two options.

    a) The idle speed of the motor needs adjusting(air2fuel ratio might be off,can this be adjusted?

    b)Have I disconnected the oil sensor properly(is it as simple as disconnecting the yellow wire or is there any thing more technical I need to DO?

    Your thoUghts are muchly appreciated.!!!thanks Al:sweatdrop:
    Last edited: Feb 2, 2010

  2. Old Bob

    Old Bob Member

    try letting it warm up a little, don't apply full throttle with choke on
  3. Atudge

    Atudge New Member

    Ive tried Bob,Ive tried to ever so gently feather the throttle to keep it running till it warms in the hope that it might find some rythm but cuts out.However I might try putting the motor in a very warm area(airing cupboard etc) to see if that helps before starting?

    Could that be a possibility?

    Appreciated Al
  4. When you snap the throttle back does it want to cut out? I had the same problem but my GXH50 would idle. I had to clean out the jet in the carb. really good. Is this a new build? New tank and fuel line?
  5. HoughMade

    HoughMade Guest

    I know you said the carb was clean...but mine was too...until I ran it a bit.

    Also, I had similar issues once when my home made gasket covered a small hole on the carb.
  6. Atudge

    Atudge New Member

    Kline yee kind of you have to be ever so gentle with the throttle to mantain an idle before cutting out..Could it be something to do with the float in the carb.That looks clean and operates smoothly once I took the cup off tho hmmm.What method did you use to cleam the jets I think thats got to be worth trying?

    Hough yee I see your point,I might investigate the carb to be worth trying

    Thanks Al
  7. Irish John

    Irish John Guest

    Atudge, Are you sure the choke isn't on. If it's on it will behave like you describe until you switch it off. That is the first thing that springs to mind. The air/fuel screw comes at the correct setting on a Honda motor. You shouldn't have to adjust it but it is easy to adjust correctly. There might be a bit of gunk in the carby jet especially if you aren't using a good fuel filter. I clean the needle & seat using compressed air from a big hand pump with the nozzle held over the fuel line barb on the carby & that usually works well. I've always noticed dripping fuel from air filter box when gunk gets in needle/seat.
    I think it's the choke or the needle/seat in that order.
    You shouldn't need to touch the oil cut off switch on a Honda because they work fine leaving them as they are.
    Is your throttle working perfectly?
    Is the kill switch wired up correctly?
    Are you using a Honda carb or a HS carb?
    Good luck
    Last edited by a moderator: Feb 5, 2010
  8. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Atudge,

    Just a quick comment. Sounds like carburetor issues, however it is very IMPORTANT to use air to clean passages in a CAREFUL way.

    If you use air under pressure with the float bowl attached you can crush or distort the float. I always remove the float bowl when using air to force any blockage from the carburetor passages.

    The problem you describe sounds very much carburetor related, however make sure the tank's fuel flow is correct [open fuel shut-off with line disconnected to make sure].

    Have fun,
  9. Stan4d

    Stan4d New Member

    I read somewhere that someone used the in tank filter in addition to an inline filter causing a similar problem. Turns out the cheep tank filter was the problem.
  10. Atudge

    Atudge New Member

    Hello guys thanks for your help I agree it does sound carb related I have thorughly cleaned the carb in the most delicate of manners ensuring float is taken the very best of british care.

    Irish john I have noticed fuel running down the face of the air filter box like you have mentioned in your post.Although im sure upon doing my sugical clean of the carb i would have released any gunk from the carby.Can you tell me the method in simple terms as to how you cleaned properly the needle and seat...and also where the air to fuel screw adjustment can be found just incase the engine has been tinkered with ....could possibly of been accidently upset along the way.Does seem to be running very very rich from the exchasut emmissions

    Kindest of regards Al
  11. Irish John

    Irish John Guest

    Sure can Atudge. Just give me 30 mins to compile something with pictures.
  12. Atudge

    Atudge New Member

    Irish john your efforts are veyr much appreciated! Thankyou kindly
  13. Irish John

    Irish John Guest

    OK Atudge here are the pics with notes and also a PDF file. The pics belong to another kind MBc member's who posted this over 2 years ago and it is all self explanatory but I have annotated them for you. It is quite usual not to get the carb totally clean first try but the second go should get it right. If fuel is leaking out the air filter it can only be gunk in the needle seat because I'm sure your float hasn't got a hole in it and if it floats it will do the job and push the needle onto the seat to cut off the fuel. Take care and be very hygeinic and clean about the process. I've found little bits of stuff in my needle/seat that look like seaweed! The PDF is just more instructions courtesy of one of the old timers on MBc.
    You can't beat MBc for finding things out can you?
    If they read this Forum in China we would be out of business!

    Attached Files:

  14. Atudge

    Atudge New Member

    Thankyou very much irish john I will set to it straight away and inform you of the outcome
  15. Atudge

    Atudge New Member

    Ok so I have given the carb a thorough and delicate clean of all the items listed in the pictures provided..I fired her up and it ran better but then cut out.. bugger!!

    So I tried what else you showed me which was the air/fuel and after have small adjustments to that It starts and runs like normal without the choke on or if it needs to be on its only on half as much.It sounds a lot stronger so Im presuming something along the line has upset the air/fuel and its been running very rich hence the fuel out the filter.I think the air/fuel still needs a small amount of tinkering as it still seems a little shakey but on the hole a vast improvement.

    I reckon the slightest of turns and it will idle perfect.

    Thanks for your help I wouldnt of been able to get this far without it! Cheers Al
  16. Irish John

    Irish John Guest

    I think you are nearly there Atudge. Maybe ask a local mower engine repair shop or motorbike man to adjust it for you if you have problems. He probably won't charge you for it and will show his method of doing it.
    Glad to be able to help someone.
  17. kadude

    kadude New Member

    You know? I had the same problem with my HS 4-stroke..I was about to tear apart the Carb and if that didn't work..I was gonna call and get an exchange on the engine via Warranty..

    Frustrated! I was ready to grab the tool box..I finally took a deep breath and decided to check the fuel switch..Why not since I have checked just about everything else...

    Sure enough the Fuel switch was on quarter open on the fuel tank..Runs like a Charm now..
  18. Irish John

    Irish John Guest

    It's always something really really simple isn't it Kadude. Like how HoughMade suggested to Atudge earlier that the first thing to check is a blockage in the fuel supply - usually on the inside of the tank around the little filter or in the on/off hosecock.