Engine Trouble Tops out at low speed,

Discussion in '2-Stroke Engines' started by bailsafe, Oct 21, 2015.

  1. bailsafe

    bailsafe New Member

    Hello! I just finished my first build. It's up and running as of today, but the engine seems to really bog down when I'm above 50% throttle. For instance, I topped out at 11mph going up a (not extreme) hill, and that's with pedaling, on a 66cc Chinese motor. On flat ground, I topped about 15mph.

    The engine sounds a lot more powerful full throttle with the clutch disengaged. Would that have anything to do with it? Any suggestions? Thanks in advance!

    BTW, I'm using an 18:1 fuel mix for break-in. Carb was halfway open.

  2. jaguar

    jaguar Well-Known Member

    with the clutch in does it take longer than normal to get back to idle after cracking the throttle open?
    (this is assuming you have experience with 2 strokes and know what "normal" is)
  3. bailsafe

    bailsafe New Member

    Doesn't take longer than normal, it idles pretty quickly after disengaging the clutch.
    Last edited: Oct 21, 2015
  4. jaguar

    jaguar Well-Known Member

    if you blip the throttle and then it doesn't go right back to a normal throttle (it stays high idle for awhile) then you have an air leak. where?
    1) intake tract
    2) crank seals
    3) head/cylinder junction

    that makes it run too lean which is why it loses power when you make it even leaner by opening the throttle all the way while riding
  5. butre

    butre Well-Known Member

    I'm betting on compression leak
  6. crassius

    crassius Well-Known Member

    could be as simple as choke left on

    don't get in a hurry to fix it until much more general reading is done here about how these work & common problems that are seen with new builds