Throttle/Acceleration Problems

Discussion in 'Motorized Bicycle Trouble Shooting' started by JoshuaYoung, Dec 17, 2013.

  1. JoshuaYoung

    JoshuaYoung New Member

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    Hello, I've has my bike for about a month now! I was noticing that when I'm riding it and go full throttle, the bike slows down like it wants to shut off after about 4 seconds! I don't know what can be the problem!! Anyone have any tips?
     
  2. crassius

    crassius Well-Known Member

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    bad vent hole in the gas cap comes to mind - loosen the cap & see if the problem goes away
     
  3. 2door

    2door Moderator
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    It would help if we knew what engine and carburetor you have.
    It's hard to make suggestions if we don't have some basic information.

    Tom
     
  4. JoshuaYoung

    JoshuaYoung New Member

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    I will try the gas cap tomorrow! And I have the regular 80cc engine ! Nothing fancy! And I have the stock carburetor !
     
  5. GearNut

    GearNut Active Member

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    There are no 80cc engines, only bad marketing and lying that they are actually 80cc.
    You most likely have a 66cc engine.
    There are 5 kinds of "stock" carburetor.
    NT, NT Speed, CNS V1, CNS V2 and CNS V3.

    Where did you buy it from?
    Can you share a link or perhaps a photo? Some way we can get a better idea of the engine in question and what you have on it?

    My blind guess is either the aforementioned gas cap problem or the carburetor's float height is set too low. It could be a poorly flowing petcock too.
     
    #5 GearNut, Dec 17, 2013
    Last edited: Dec 17, 2013
  6. 2door

    2door Moderator
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    Has this problem been there from the first or something that has recently become a issue?
    I concur that a restricted fuel system might be the problem. Are you using an in-line fuel filter? Did you clean and flush the fuel tank before installing it? Have you disconnected the fuel line from the carburetor and checked for a constant flow of fuel from the tank?

    How does it idle?
    What is the spark plug gap? What fuel to oil ratio are you using?
    All of these can have an effect on how the engine performs and cause the symptoms you describe if not correct.

    Tom
     
  7. JoshuaYoung

    JoshuaYoung New Member

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    Yes this has been a problem before but never to the point where the engine slows down this sudden ... The problems I've had

    1. I've replaced 2 clogged fuel filters
    2. Replaced a petcock last month with one that still flowed but not as strong because it had paint chips
    3. The carberutor tends to leak and fill with gas through the air filter
    4. The fuel ratio I use is 4 ounces of oil to 1 gallon! I'm supposed to be using 2 ounces!

    So based off of all these problems , can you guys give me a list of things to do in order to troubleshoot my problem
     
  8. GearNut

    GearNut Active Member

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    1. Clean out the fuel tank thoroughly. As they come from the factory they are known for having rust and junk inside them.
    2. Clean out the petcock.
    3. Fuel leaking out of a carb is a sign that there is debris stuck in the float needle valve, the float height needs adjustment or the float has a pinhole and has taken on fuel.
    This is assuming that the carb is sitting flat and level or pretty close to it, depending on how the engine has been mounted.
    4. If you are using dino oil then a 24:1 ratio is good for break in. 32:1 is good after that for the rest of the engine's life.
     
    #8 GearNut, Dec 18, 2013
    Last edited: Dec 18, 2013
  9. JoshuaYoung

    JoshuaYoung New Member

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    I tried to ride it with the gas cap loose! Still no luck ! I took off the air filter and it was soaked in gas! Do you think the carbeurtor was the problem? If so I might just buy a new one !
     
  10. 2door

    2door Moderator
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    Before you invest in a new carb try the suggestions Gearnut offered. You might save yourself a few bucks. Typically there is little that can go wrong with the carburetor. The biggest problem is usually a clogged needle valve or a cracked float that has sunk.
    Check those things before spending your dollars.

    Tom
     
  11. JoshuaYoung

    JoshuaYoung New Member

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    Do you think that can be the problem though? The bike accelerates at full speed then seems to choke! I took off the fuel hose from the carb and it flowed perfectly ! So I'm assuming its a flooded carb! Can a flooded carb or the float problem cause my issue I'm having?
     
  12. crassius

    crassius Well-Known Member

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    Could also be fuel foaming in the bowl if the vibration is too great, or possibly the main jet is too rich causing spit-back & 4-stroking.
     
  13. JoshuaYoung

    JoshuaYoung New Member

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    Is the jet apart of the carb? Basically I'm a noob to this stuff sorry! What should I buy to help me resolve my problem? A new carb? I know a guy who sells motor bike parts near me
     
  14. GearNut

    GearNut Active Member

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    Do not buy anything until you have thoroughly inspected the parts you have for problems/ adjustments needed.
    Unless you like to throw money at problems until they go away.

    Carburetors are very simple to work on. The hardest part is keeping the guts clean, and even that is not hard if you take precautions.
    Cut out the side of a cardboard box and use it as a place mat on the table or work bench you are working over. This insures that no dirt or grit gets picked up by the parts when you lay them out. Use a cardboard egg crate to hold each part in order of dis-assembly. This makes it much easier to reassemble in the correct order and also insures that no parts were accidentally left out.
     
  15. JoshuaYoung

    JoshuaYoung New Member

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    Are there any videos on how to adjust the carb ?
     
  16. GearNut

    GearNut Active Member

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    Which carb do you have?
    There are videos on utube and some folks here have made how-to threads with good pictures.

    Also, crassius brought up a good point: Does the engine vibrate alot?
    Too much vibration will cause the fuel to foam inside the carb and negatively affect the carb's ability to properly meter the fuel.

    Are you familiar with a 2 stroke engine 4 stroking? Do you know what it sounds like and the performance loss associated with it?
     
  17. JoshuaYoung

    JoshuaYoung New Member

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    I don't know anything about the sound! I am a noob! How would I stop the vibration in the carb?
     
  18. MotorBicycleRacing

    MotorBicycleRacing Active Member

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    What Carb do You have?
     
  19. 2door

    2door Moderator
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    Is your engine mounted solidly to the frame? You're not trying to use rubber or something soft in the engine mounts are you? That will cause more vibration and can result in fuel foaming. Extreme vibrations can cause the problems you're having.

    Tom
     
  20. GearNut

    GearNut Active Member

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