Engine bogs down

Discussion in 'Introduce Yourself' started by thermax, Mar 5, 2012.

  1. thermax

    thermax New Member

    I just finished building my first bike, the beach cruiser with a 66cc engine. Not sure what kind of carb it has other than its very simple with just a throttle cable coming out of the top. I took it out tonight and found it works very well until it get warmed up and than it bogs down at high speeds and feels like its going to stall until I let off the gas a little. I tried reaching down and giving it more choke but that made it worse. Do you know if there is suppose to be a gasket where the carb attaches to the manifold? Could this be an air leak or does the carb need an adjustment. I live in Florida. thanks so much
     

  2. ddesens

    ddesens Member

    Sounds like your running rich.{too much fuel} Try moving the main needle down a notch with e little e-clip. That will allow less fuel into the engine over the entire rpm range.. Just a thought.
     
  3. jeffuehrer

    jeffuehrer Member

    Congratulations thermax! Yes, there should be a gasket attached to the intake manifold. First try choking it all the way. If it dies immediately you probably don't have an air leak. If it takes longer than three seconds you might have an air leak. If you haven't read the newbie tips yet you might want to start there. Some people spray carb cleaner where the carb attaches to the intake tube while the bike is running and if there is a noticeable difference you probably have an air leak. I learned about building my bike from the top down and it took twice as long as learning about it from the bottom up.
     
  4. ddesens

    ddesens Member

    There is a gasket from the manifold to the engine cylinder. Usually the carb just slips onto the intake manifold pipe and clamps with a screw. Many people including myself put an o-ring in between the carb and manifold pipe to eliminate the chance of an air leak or you could coat the end of the pipe with some rtv sealant and slip the carb back on a tighten it down to eliminate an air leak.
     
  5. motorpsycho

    motorpsycho Active Member

    Normally a bog at high speed is caused by the air-fuel ratio being too lean, not too rich.
    if it's too rich you will get a bog on take off and at slow speeds.
    the cure for this?
    you may have to re-jet the carb.
    moving the slide needle up (by moving the c-clip down) will only help the air-fuel ratio from idle to about 3/4 throttle. raising the needle up (move c clip down) will richen the mixture, lowering the needle down (move c-clip up) will lean the mixture.
    BUT, after 3/4 throttle, the main jet takes over 100% and the needle is completely out of the picture. moving the needle will not make any changes to the way it runs at wide open throttle.

    also, if you are still on the "break in" fuel-oil mixture of 16:1 (as suggested by almost every manufacturer of these engines), this mixture will actually create a lean air - fuel ratio condition because there's so much oil in the fuel.
    change it to 20:1 and see if that helps.
    once the engine is broken in, try going to 32:1
     
    Last edited: Mar 6, 2012
  6. thermax

    thermax New Member

    plug seems to help problem

    I was able to correct the problem by replacing the spark plug with a 3 prong plug. I reset the adjustment clip back down one notch from the top. It ran good on the top notch but I was afraid it was running to lien.
     
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