tricky...tricky...tricky...

Discussion in 'Motorized Bicycle General Discussion' started by MatCauthon137, Jul 17, 2010.

  1. MatCauthon137

    MatCauthon137 New Member

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    ok, so i am running a grubee skyhawk 48cc 2 stroke, thought i had an air leak. i have sealed up everything i can think of, yes I put permatex on the intake of the carb, checked the carb and intake for other leaks using carb cleaner. problem is i have a major loss of power and i leak fuel...ok to be fair, it only leaks fuel AFTER the engine has been shut off, and only then from the exhaust pipe, but none of my other engines has ever done that...also, the leak is small, i put a bowl under it last night to catch and measure and this morning i had maybe 3 tablespoons of fuel in the bowl...any ideas?:-||
     
  2. 2door

    2door Moderator
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    Check your carburetor float and needle valve. Your problem sounds like some trash has gotten into the valve not allowing it to close and giving you a rich/flooded condition and excess fuel is finding its way out. Get back to us if this doesn't solve your delemma.
    Tom
     
  3. Mac

    Mac New Member

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    I had one of mine do almost the same thing, although a bit more fuel, turns out the carb. float had a hole in it, turns out to be fairly common with the Chinese carbs. Only a few dollars from any vendor.

    Mac
     
  4. azbill

    azbill Active Member

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    I have gotten carbs with the float installed upside down as well
    (the seam on the bottom, allowing gas to seep inside causing them NOT to float)
    just something else to check ;)
     
  5. MatCauthon137

    MatCauthon137 New Member

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    not the float...my wife's bike i built her is running great, so i tore apart her carb and took her float, he bowl was completely empty of fuel when i took it off...i then took mine off, the bowl was filled with fuel, and the float was floating...time to move on the the valve, it has got to be the needle valve, right?zpt
     
  6. HeliHaole

    HeliHaole New Member

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    Mine was doing the same thing, 2Door is right take it apart and double check that there is nothing in there, also bend the float tangs down just a c-hair so that the float shuts the fuel off sooner
     
  7. 2door

    2door Moderator
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    Here's a simple check for you. Leave the bowl off, turn the fuel petcock on and gently, very gently, push up on the little brass fork that sits on top of the float. If the fuel stops flowing then the needle valve is working properly and clean. If it doesn't then look for trash stuck in it or a damaged or misaligned needle/seat. As was suggested you can carefully bend the fork fingers downward slightly, just a little, and see if lowering the float level doesn't cure your problem. The lower the float, the sooner it shuts off fuel flow into the bowl and lowers the fuel level in the bowl which can slightly lean your mixture. Make sure you bend both forks the same.

    Tom
     
  8. MatCauthon137

    MatCauthon137 New Member

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    Time to stop for the night, but here is what i have learned so far...first off, i think i may still have an air leak around the intake of the carb (carb cleaner stalls the motor when sprayed there). The air hole that goes from the air filter into the bowl was NOT drilled out properly, so not enough air was getting into the bowl (and that is chinese quallity control). So I drilled that out, and whoa, increase in power, at least now it will run with a choke. Tomorrow, i take 2door suggestion and try lowering the float, also the petcock test (can never be too sure). I have some copper rtv that i will then put around the outside of the carb where it connects to the motor intake (that is the right place for it, right? I wouldn't want to put it inside cuz it says not to use on anything that comes into contact with gas, so I am assuming that would be an exercise in futility) so i assume i am to tighten carb on motor as much as i can, then use rtv on the outside around where it connects...if i am wrong, will someone let me know, i don't like looking like an idiot, lol. .spr.
     
  9. 2door

    2door Moderator
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    You're not an idiot and there is no such thing as a stupid question.
    There is a product that I've had very good luck with called Seal-All. It is gasoline compatible and does a heck of a job sealing the intake at the carburetor. It looks and smells like old Ambroid model airplane glue but does the job. I like to fill the slots in the carb throat where it clamps to the intake manifold to assure against air leaks. Also check carefully the gasket sealing at the intake manifold and the cylinder. Give this a try and get back to us with the results. The only thing that concerns me is your comment "at least now it will run with a choke" What do you mean by that? The choke should be wide open (lever fully down) for it to run properly. Good luck.
    Tom
     
  10. corgi1

    corgi1 New Member

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    New gasket between the manifold and engine?
     
  11. MatCauthon137

    MatCauthon137 New Member

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    I know i probably don't have to, especially in hot weather, but i usually start the bike with the choke on then turn the choke off once the motor (warms up) which is this weather is really fast...the problem was, with the choke on the bike wouldn't even start, which is why i began thinking i had an air leak in the first place. now i have been starting her without using the choke at all, but to test her and make sure i was getting somewhere, i would let her idle and put on the choke, just to see if it would kill the motor. all i meant was now it will idle with the choke on, so i think she is getting more air, but you are right, i wouldn't take her out for a ride full throttle with choke on, that could be bad.duh.
     
  12. 2door

    2door Moderator
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    Mat,
    Maybe I'm missing your point but maybe also you have it backwards. If the engine idles with the choke on, (closed, lever up) then you definitely have an air leak. If everything is sealed up well, choking the engine will stop it. In fact there are a number of guys who rely on the choke to kill their engines because they do use a kill switch. If I'm misunderstanding you, let me know but if your choke is closing properly but doesn't kill the engine start looking for a leak.
    Tom
     
  13. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    The fuel comming from the exaust pipe can't be comming from the carb.. (The whole crank case would have to fill up first, & even then, the intake port is lower than the exaust.)

    The fuel comming from the pipe is probably just unburnt fuel sitting in the pipe.
     
  14. Goat Herder

    Goat Herder Gutter Rider

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    Just pm me and I will straighten you out in person.
     
  15. bairdco

    bairdco a guy who makes cool bikes

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    actually, depends on the position of the piston. if the piston is right at the bottom of the intake port, then the fuel can fill up a small portion of the cylinder and flow right into your exhaust port. happened to me once when my petcock failed.

    most likely cause is unburnt fuel from a rich mixture, though, like Venice said, unless it's a lot of fuel.
     
  16. MatCauthon137

    MatCauthon137 New Member

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    ok, that i didn't know. I thought it should run either way, just not run well. ok, so i did some more work on her...still got to be an air leak, she has no power, but the choke kills it now...

    i did the petcock test..removed the bowl and opened up the fuel line, then i pressed up on the needle, and the fuel flow shut off, just to be safe, i bent the prongs down a bit to shut off fuel flow sooner.

    I checked the float, and it is floating in the bowl (put some fuel into bowl). i did notice a small fuel leak from the fuel tank (the shut off valve was not screwed in tight enough, but i don't think that's related to this problem).

    i replaced the gasket between the intake manifold and the engine, although that gasket looked fine to me, i replaced it anyway

    i removed and cleaned the air filter (although it is brand new so...) and i am going to put some silicone sealant where the carb connects to the intake manifold. i haven't (however) gotten a chance to test all this because it was time to leave by the time i got all that done, so hopefully i can test tomorrow since the sealant takes a day to cure.
     
  17. MatCauthon137

    MatCauthon137 New Member

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    maybe i am expecting too much? ok, so i tinkered around with her and got rid of all the air leaks (that i can find). I spray carb cleaner everywhere i can think of (between the intake and the motor, between the intake and the carb), and the motor does not stall. The it will not run with the choke on, and will idle perfect. Going downhilll, well that's easy. and going on flat land, she flies. it's all stock parts, so i don't expect to start going from a dead stop without pedaling first...however...

    this is albuquerque, and we are full of some pretty steep hills...she can take some of the lesser hills, i have to pedal to get her started up the hill (even if i have already been going) and if the hill is long i have to pedal again about the middle of the hill to help her out, steep hills i have to pedal the whole time to help her out...lack of power going uphill...

    normally, being a noob, i would say this motor is pedal assist and that's fine, except my wife also built a bike, (different motor to be sure) and hers takes all of these hills no problem without her having to pedal at all...

    details:

    my bike: huffy cranbrook beach cruiser
    my motor: grubee skyhawk 48 cc
    me: about 135 lbs (yeah yeah)

    her bike: greenline bc-105 beach cruiser
    her motor: grubee starfire 48 cc
    her: about 120-130 lbs

    am i doing something wrong or am i just expecting too much from a stock motor?.trlrl.
     
  18. Goat Herder

    Goat Herder Gutter Rider

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    #18 Goat Herder, Jul 22, 2010
    Last edited: Feb 28, 2011
  19. MatCauthon137

    MatCauthon137 New Member

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    then here is some more info for you so you can judge this a little better, thanx goat herder...tramway is a piece of cake for this bike, but she has difficulty going east on lomas between juan tabo and tramway, that is where i need to pedal to help her...
     
  20. Goat Herder

    Goat Herder Gutter Rider

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