power in low end, barely runs after warm up

Discussion in '2-Stroke Engines' started by chancecube, May 30, 2011.

  1. chancecube

    chancecube Member

    I can start my bike while barely moving, light pedaling. Before my bike warms up it runs great, all the way up to 27mph. After it warms up, getting any pull out of the motor while under 18-20mph is rare, mostly A lot of bucking and and cutting off. If i can keep the bike above 20 and under 27 at all times it turns out to be a good ride. Cant go over 27 because of 4 stoking which should mostly go away after break in. I had a over heat problem earlier which was due from too much oil mix. 16:1
    The motor is a 66cc gt-5.
    83 miles ago I replaced the rings and piston.
    44 tooth sprocket and in NT carb

  2. motorpsycho

    motorpsycho Active Member

    umm, do you have the choke fully open?
  3. chancecube

    chancecube Member

    NO. I only use the choke to start.
  4. olow

    olow Member

    sounds like a air problem to me check the head and carb
  5. chancecube

    chancecube Member

    the motor has all new gaskets. head is sealed good. and carb too.
  6. rustycase

    rustycase New Member

    If it's four stroking, it's running too fat.
    No two ways abt it.
    Lean it out some and see what happens.
    It will improve, or it won't.

    Two strokes are notorious for running crappy when cold, and running like a madman once they are good and warm.

    If yours does not do that, your fuel/air mix is wrong.

  7. tone2crazy

    tone2crazy Member

    you said you replaced the rings and piston. was the cylinder wall free from any scatches?
  8. chancecube

    chancecube Member

    the cylinder wall did have a scratch
  9. tone2crazy

    tone2crazy Member

    that means its siezed. even if its what some people call a soft sieze. a new ring can make the scratches worse. take the top end apart and see if the scratches are worse. you very well might have to replace the jug and get another piston/ring.
  10. rustycase

    rustycase New Member

    I'd like to disagree with that, T...

    Now that we have a scratch to consider, we need to figger how it got there.
    Could be from build-up of combustion chamber debris, (carbon fouling), a broken ring, chunk of a piston, chunk coming in through the intake, or internal engine parts from a casting flaw.

    Many years back I lost a cable end from the carb slide and it buggered up the piston crown and cylinder head. Could have just as easily lodged in a place to score the cylinder wall.

    ...So tell us more about this scratch!
    Is it there now? or was it there when the last rebuild was done ?

    Do you run an air cleaner??? :)

  11. tone2crazy

    tone2crazy Member

    yeah the weirdest thing can sieze a motor. i once ha the screw holding the butterfly(gp460) on come off and destroy the top end
    and i believe he said the scratch was there when he replaced the piston/ring.
  12. rumpnuts

    rumpnuts New Member

    there was a broken ring which i replaced the piston and rings, the scratch wasnt that bad. wasnt all the way up the cylinder. only about 1.5 inch long. I used the stock air cleaner on the carb.
  13. tone2crazy

    tone2crazy Member

    thats a pretty big scratch. i would take off the jug and see if its worse.
  14. yeah cylinders dont handle scoring very well. you may be loosing compression from it and or the rings are catching on it. you may even have another broken ring if you took it apart and looked... the symptoms at firsted sounded to me like a head gasket. but now that the scoring was brought up im sure that is it and you are loosing compression from it. new jug, rings, and maybe a new piston sound to be in order..