honda gxh50 fuel problem

Discussion in '4-Stroke Engines' started by sexwaxsurfer15, Dec 28, 2008.

  1. I just put a new gxh50 on my motorbike. The problem is that when I try to start it up, it tries to start(i can keep it running a little bit by switching the choke on and off but it eventually dies, this is at lot rpms). I ran a line strait up from the carb and filled with fuel. Still same problems. Im confused anyone got a suggestions?:confused::rambo:

  2. ocscully

    ocscully Member

    There is a low oil circut/sensor on the GXH50. It will allow the motor to start but as soon as it senses low pressure it shuts the motor off. Make sure your oil level is where it should be first, and then be sure that the wiring for this sensor is not shorting out.

  3. im getting a spark, doesn't that mean that the oil is ok?
  4. i think im messing up the connections. There are two yellow wires that come off the engine and a black female connector on the engine. The kill switch has a yellow wire with a red stripe and a green wire. Can someone help on the schematics?
  5. ocscully

    ocscully Member

    Here is a link to the Honda GXH50 owners manual the wiring diagram is on page 15.

    With the oil sensor wired in and low oil level the motor will start nad run briefly
    (perhaps 10-30 sec.) So yes you could still be getting spark and the problem could be low oil pressure/oil level. But it could easily be a short as well. Hope the diagrams help.

  6. Ok everything is hooked up right and the oil level is right. It is still doing the same thing. Can get it started only with choke on and the only way it stays alive is if i mess with the choke every 2 seconds. Its running at super low RPM's too. I had it running excellent the first time i started it(new engine). I let it sit for a day and now its like this? Any suggestions? How can I check if the low pressure sensor has shorted out? I have a feeling this is the nature of my problem.
    Last edited: Dec 30, 2008
  7. Mountainman

    Mountainman Active Member

    it would be nice to know
    if it's running lean or rich

    sounds lean -- lack of gas ?

    new engine that was running fine
    wonder if there may be a small piece of ?? stuck in the carb, fuel line or filter ?
    float should also have smooth action -- wonder if it does ?

    just putting it out there -- ride that THING
  8. its definately getting gas to the carb and there were 2 fuel filters in the line before the carb so there cant be anything in the carb.
  9. Mountainman

    Mountainman Active Member

    what does your plug tell you
    too much or not enough gas
    could be a starting point

    with the carb
    I was thinking a little something in there from possibly when it was made
    kind of a long shot

    two filters -- I would only use one -- could two restrict flow ?

    if we need to run with the chock on a little so as to keep running
    tells us -- we are lacking gas -- usually

    ride that thing
    Last edited: Dec 30, 2008
  10. Honda50

    Honda50 Member

    In the course of shipping the engine, it will get tossed about and possibly the float assembly/needle valve took a hit.

    When you use the choke, you are actually enriching to compensate for a fuel starvation condition.

    OK, the oil level is correct.
    As you pull start the rope, can you 'feel' the engine's compression? (this is a quick-check of engine compression)
    We have spark at cranking and running. You say the engine ran good at first.
    We have fuel reaching the carb. ***ensure the fuel shut off valve on the carb is in the full OPEN position***. Take a fuel sample, let it settle in a clear class jar. Is the fuel contaminated? There is a small fuel filter inside the fuel line at the fuel tank outlet. Pull the hose off the tank and you will find the filter either in the hose or stuck up in the tank outlet hose fitting. Ensure it is clean.

    Do a good visual inspection of the throttle linkage and governor linkage to check for possible shipping related damage. Ensure the carb mount bolts are secure and snug. This will check for a possible vacuum leak. Manually open and close the throttle. Is it smooth and non binding?

    Remove the air filter cover and inspect carb throat with a light. Perhaps turn IN (clockwise) the throttle stop screw one turn and try to start engine normally. This will compensate for a mis-adjusted curb idle speed setting (throttle closed too much at idle to run properly).

    Still no luck? Everything looks good up to this point? I would suspect a carb idle circuit problem. This is where you clean off the ole work bench and have a fresh can of Carb Cleaner on hand. Remove air cleaner assembly and gently remove carb from engine, taking care not to damage the gasket. Working on a clean work bench is a must! This has to be a clean operation. Clean fingers too.
    Remove float bowl. Invert carb and take care not to damage the float assembly. Check to make sure it's not obviously out of whack. Remove the float and needle valve parts and lay out neatly. Now, shoot carb cleaner (through the little red tube that comes taped to the can) into every orifice and passage you can find in the carb body. Use compressed air to follow up all the passages and to dry off carb of all cleaner. Use that compressed air in a can if you have no access to compressed shop air. Additionally check all of the passages for flakes of casting flash or machining chips from the manufacturing process. Carefully reassemble the carb after inspecting the needle valve tip for deformation or debris.

    Fire that puppy up and cross your fingers.

    I'm curious as to what you ultimately find! Good luck. It's usually something very simple and stupid.
  11. Honda50

    Honda50 Member

    A suspected "stuck float" can possibly be remedied by LIGHTLY tapping the carb float bowl area with the handle of a screw driver. The vibration may un-stick it. It may not. This may assist in clearing up a no fuel problem or a flooding problem if related to the float. Be easy here. We don't want to whack it so hard that you end up sheering the carb off the engine:evilgrin:.

    I always treat my fuel with Pri-G. It tends to prevent or minimize fuel related fouling of the carb (gumming and varnishing) while sitting over time and not being used. Maintain a clean air filter at all times. Your piston rings, lands, skirts and valve faces/guides will last a lot longer. So will internal bearing surfaces. The engine oil will remain cleaner from external abrasive particulates.
    Last edited: Dec 30, 2008
  12. TWalker

    TWalker Guest

    Make sure you have oil and then disable the low oil sensor (mine stays off) by disconnecting the wires. That will at least rule out a malfunctioning low oil sensor.

    I cannot ride mine with it connected because it shuts off every time I hit a bump, which is why I know to unplug it anyway.
  13. HoughMade

    HoughMade Guest

    Clearly this is fuel related. If it was the low oil, he couldn't keep it going by fiddling with the choke.

    Are the governor linkages freely moving? What about if you control the engine speed with the throttle butterfly directly instead of the governor?

    Also, take the fuel line off the carb abd let it run into a gas can. Does it run 100% freely? It should not dribble, it should be able to gravit drain about 1/2 gallon in 2 or 3 minutes.

    You say you used 2 filters, but I never ran without a filter and still got stuff in the carb. Are your filters paper filters or something like this?

    If it is like the one linked above, it is a screen filter and will let large enough bits in to clog the jets. Guess how I know that. Only use a paper filter something like this:

    There are many good ones and one is plenty.

    Unfortunately, once the carb is clogged, the only way to make sure it is good to go is to take it off and clean it part by part. Again, guess how I know.
    Last edited by a moderator: Jan 8, 2009
  14. Irish John

    Irish John Guest

    Yes I'll bet you the answer lies in HoughMade's & Honda 50's comments. I'd first check that the shonky little filter inside the tank isn't blocked and that the shonkier HT fuel cock hasn't got dags of alloy that are blocking the flow. I'd take the whole fuel cock assembly out and throw it over the neighbours fence and buy a brass barb to fit the tank and a on\off inline fuel switch and use a paper filter. Then if the problem is still happening I'd take the carby apart as per the instructions above. All the new Hondas have that cursed low oil cut off and I'm glad I read that it needs to be disconnected because it operates on bumps. Is this absolutely true? All my previous Hondas didn't have this oil cut off thingy.
    It has to be the fuel line that is causing this problem somewhere between the carby and the tank.
  15. HoughMade

    HoughMade Guest

    I run the low oil switch without any problems.

    Also, the GXH50 I have has a fuel shutoff at the engine, so like you said, I just have a barb and a hose that runs to the filter and from the filter to engine.

    Attached Files:

  16. Irish John

    Irish John Guest

  17. TWalker

    TWalker Guest

  18. fetor56

    fetor56 Guest

  19. Honda50

    Honda50 Member

    I have the rear mounted rack Staton gear/chain drive set up. If I go over some really rough bumps, at high speed, my engine will stall. I kind of expect it to stall over such a surface and besides it's seems to be unsafe under such conditions, ripe for a wipe out or close to it. Whether the stalling is caused by oil slosh or fuel bowl slosh, I don't like taking the bike over such rough paths at high speed anyway since it is not good for the bike in a general way, like my rims. I don't beat on my expensive toys. Sometimes you just can't help it. For me it's somewhat rare to stall out, but it has happened to me too. I'm not too concerned. So, when I do stall out, I get the feeling I was riding too fast over too rough terrain. So now I try to match the speed to the terrain or road surface when possible. And that seems to work out for both bike and myself.

    With any four stroke, mounting it level as mentioned above is critical. On my set-up, I have to take into consideration what final position the engine winds up in after the chain tension is set. The engine pivots on a long bolt just behind the seat for adjustment. I have already removed a link or two from the chain to compensate for chain break-in and allow the engine to remain in a near level operating position to ensure the crankcase oil is level as well.
  20. GreenMantis

    GreenMantis Member

    I know this is an ancient thread, but I came across it, and right away I knew what it was, and can't get over that feeling of the kid in class waving his hand in the air, "I know! I know! I know!": This is a vaccume leak, probalby the manifold gasket, you are sucking in air somewhere, choking the carb enriches the mixture enough to compensate. This engine should not be able to run at all with the choke on, period, and if it can, then you are sucking in extra air, someplace. I went through a lot of this adapting a walbro type rotary valve carb and it's manifold to my engine, by trial and error.