Engine runs great, but having throttle trouble - VIDEO INSIDE

Discussion in '2-Stroke Engines' started by keylan, Apr 13, 2009.

  1. keylan

    keylan Member

    Alright guys, i went for a ride today, was out for about an hour or more, came home, parked it, and then about 3 hours later i went for another ride... there was a bit of trouble starting and once it got going it raced up to max RPM, a quick adjustment to the throttle cable and all was well for RPM count, however every time i rev it up it will hold the RPM's or increase to full and stay there, I have put about 150-200 miles on this build without any problems

    and before my long ride this morning i cleaned the carb out 100% and then went for the long ride so i can assume this issue is not the carb


    My first assumption was gas that was too lean, so i drained the tank, and put in some 20:1 (usually run 32:1) and the problem continues


    here is a video of me revving the engine so you can hear the RPM's stick

    <embed width="448" height="361" type="application/x-shockwave-flash" wmode="transparent" src="http://i6.photobucket.com/player.swf?file=http://vid6.photobucket.com/albums/y246/keylan/MVI_0991.flv">
     

  2. arceeguy

    arceeguy Active Member

    You need to make sure that the throttle is not sticking by removing the air cleaner and ensuring that the throttle slide is bottoming out against the throttle stop (idle) screw.

    You may have a slight air leak where the carb clamps on the intake manifold. I wrap some teflon tape on the intake tube before I push the carb on. To test, spray some starting fluid or brake cleaner around the joint. If there is a leak, the engine RPM will change. Some say to use WD40, but WD40 leaves an oily residue. Starting fluid or brake cleaner leaves no residue.
     
  3. keylan

    keylan Member

    The throttle isn't sticking, that i checked, for the air leak, i added an o-ring right when i built the bike so i would rule that out....this is really annoying! i just want my baby fixed!!!
     
  4. arceeguy

    arceeguy Active Member

    Don't rule anything out until you have checked it.

    The only intake leaks I have ever really found were right at the carb mount. Occasionally the intake gasket was leaking because the nuts were loose. Never had a problem with the gasket that seals the case halves.
     
  5. linnix13

    linnix13 Banned

    i had the exact same problem and it was the throttle cable. i replaced the cable and that fixed the problem
     
  6. keylan

    keylan Member


    I like the sounds of that, ill go for a new cable and see what happens

    thanks
     
  7. linnix13

    linnix13 Banned

    no problem. let me know how it turns out!
     
  8. arceeguy

    arceeguy Active Member

    I thought you said you verified that the throttle isn't sticking?
     
  9. keylan

    keylan Member

    it isn't, the throttle seems to function smoothly, however at the base of the grip it looks like the throttle sheath has split open a bit exposing the cable
     
  10. Mountainman

    Mountainman Active Member

    sounds like it's hanging up ??

    ride that thing
     
  11. keylan

    keylan Member

    I'll pull the throttle cable today and see if i can trouble shoot it any

    thanks guys
     
  12. Mountainman

    Mountainman Active Member

    when I have the inside cable out of the housing
    I like to put some grease on it -- so nice

    as we ride those things
     
  13. keylan

    keylan Member

    As far as i can tell the carb and the throttle cable are functioning as designed. this is really getting me upset now...i took the carb off my other bike and that did not change anything, do you think it could be the engine?
     
  14. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Did you change the throttle cable too?

    If you have any zip ties or constrictions on the cable it
    can make the throttle stick and rev

    Loosen the path of the cable up....
     
  15. keylan

    keylan Member

    I pulled off all of the zip ties and no change, i did my best to have the throttle cable be as straight as possible, no change...i have ordered a replacement carb and throttle line, not what i wanted to do, but if it fixes my problem.... ill take it.
     
  16. Ghost0

    Ghost0 Guest

    Sounds like an air leak to me. I would check your carb to manifold and manifold to cylinder. You may also be getting a leak around the cap of the carb where is screws on to the carb body or at the cable adjuster itself.
     
  17. keylan

    keylan Member

    ok, do you have any "easy" suggestions on how to fix that? I have an o-ring inside of the carb/manifold connection....
     
  18. AlexRSS8

    AlexRSS8 Member

    Out of curiosity, did you find a solution to this problem?, What was wrong with it?
     
  19. keylan

    keylan Member

    yes, i absolutely did....it was the gasket between the intake manifold and the engine block, it had been worn out and a piece had just (it seems) rotted away or fallen off, i did a quick (very temporary) fix and it fired right up and is perfect all over again!!
     
  20. AlexRSS8

    AlexRSS8 Member

    Good to hear that mate, its not fun to have a motored bike out of service
     
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