almost closed petcock gives me more power

Discussion in 'Motorized Bicycle General Discussion' started by russty, Oct 15, 2013.

  1. russty

    russty New Member

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    ok, i've been having trouble with my motor. i got it about a week and a half ago, i've been through a total of about 5 tanks (my tank is a half gallon size). and i've maybe been topping at 17MPH, and then it slowly loses power until it maybe maxes 10 mph without me pedaling. i've been thinking that its just this infamous break-in period i've read so much about. but recently i found that when i close the petcock almost all the way it picks up speed like crazy, but my bike vibrates very violently, and it is really loud, it feels like its going to explode, so i let up a little. is that normal? please help.

    :-||
     
  2. Kioshk

    Kioshk Active Member

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    Not normal. Sounds like you're running too rich (too much gas, not enough air). Give us more detail: engine, carb, mix-ratio.
     
  3. 2door

    2door Moderator
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    Until you get back to us with some information about what you have, stop riding the bike. Running it lean, starving it for fuel, is bad. You'll do serious damage to the engine.
    2 stroke or 4 stroke? What carburetor? What fuel to oil ratio?

    Tom
     
  4. rogergendron1

    rogergendron1 New Member

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    adjust your float bowl hight !!!!

    your carb is not lvl and the float bowl needs adjusting to stop letting fuel in or it is lvl and its stuck open or just needs to be adjusted.

    bend the tab down to let less fuel in and up to let more in
     
  5. russty

    russty New Member

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    its a two stroke, i have no idea what brand or type of carb i have. i just took all the parts out of the box and put it together. so how do i let in more air, do i need a jet kit? i'm doing a 24:1 fuel ratio. which sounded really rich to me, but that was what the manual said, at least for the break in period anyway. i also live in Albuquerque which is a very high altitude place, if that means anything.
     
  6. russty

    russty New Member

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    oh, and its an 80cc.
     
  7. Nashville Kat

    Nashville Kat Active Member

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    I put up almost this same thread nearly five years ago now- more air did seem to help when I put a few more holes in the back of the air cleaner-

    the solution for me was a straight billet intake

    stopped all the bogging-

    but I think it actually worked better with the older NT carb- when I went to an NT Speed carb- the standard kit carb now, and with the billet intake- I have to choke the motor more during cold start and it doesn't want to go back to idle very well once it's revved.

    I'm thinking about putting the old nT carb back on, because with the billet, that's when my 66 was running best really.
    I ususally just ride the 50 now anyway. It's a much lighter bike, and with a 39 sprock and narrow 700c tires, it moves as fast as I want to go- low to mid 20s mostly.

    Your revving and noise and vibration may just be because you need a smaller sprock on the back- you'll hget better speed with more normal revs with a 36 sprocket
     
  8. 2door

    2door Moderator
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    The higher above sea level you are the less fuel you'll want to deliver to the engine. The air is less dense at higher elevations.

    However I wouldn't start playing with jet size until you've checked out a few things. My guess is that you have a blocked float valve due to dirt keeping the needle from seating. We always suggest installing an in-line fuel filter ahead of the carburetor to prevent that and cleaning the fuel tank prior to installation.

    The float level might be your problem but unless your engine is mounted at a very odd angle the carburetor is probably close to level. The float bowl is the little cup attached to the bottom of the carb. The float is the white plastic donut inside the float bowl.
    You can remove the float bowl and the float and push up gently on the brass tang that the float pushes against with the fuel petcock open. Pushing up on the tang should stop the fuel flow. If it still flows or drips clean the needle valve. When reassembling the float and the bowl make sure the pin the tang rides on is in the proper position and not pinched betwen the carburetor body and the float bowl.

    Tom
     
  9. russty

    russty New Member

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    i have an in line fuel filter.
     
  10. fatdaddy

    fatdaddy New Member

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    You'll notice that when it runs out of gas it will rev HARD before it dies. This is not good for the engine. What yer doing basicly is starving the engine by shutting off the gas. While I think yer running way too rich, Running it TOO lean is worse. Check yer float and inlet needle valve. Last resort is a smaller jet after you try everything else. DON'T run it like this any more. LISTEN TO 2door.
    fatdaddy.
     
  11. rogergendron1

    rogergendron1 New Member

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    again take the carb off the motor then take the manifold off the jug and inspect the manifold for casting flash, welding slag and blockages clean them up.

    take the bottom of your carb off and remove the float and float pin needle, it sounds to me your float bowl is adjusted too high or stuck open causing flooding and bogging. bend the tab ever so slightly that hold the float pin so that it sits lower in the bowl.
    this will alow the carb to shut the fuel off before it fkloods and bogs out.
    before putting the carb back together spray every channel out with carb cleaner

    change your spark plug and get it all back to gether and let us know how things go.
     
  12. russty

    russty New Member

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    The carburetor is at a slight angle. In order for it to fit in the opening of my bike.
     
  13. rogergendron1

    rogergendron1 New Member

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    this may be your prob the carb come with the bowl adjusted to sit lvl

    you should adjust your float bowl hight so it closses a little sooner .. you only need to move that tab a slight amount !!
     

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