Help Reving too high after a ride

Discussion in '2-Stroke Engines' started by heyhey13, Dec 10, 2010.

  1. heyhey13

    heyhey13 New Member

    Help I'm having a strange problem

    First of all The bike Idles correct on startup the plug is a chocolate brown
    i do the a exrtra long intake to get around bike frame

    Now the Problem
    Bike starts fine idles go for a ride and go to pull the clutch in and it rev's it's little head off push the kill switch...... does nothing bike keeps reving (by this time i have jumped off afraid of a piston leaving the engine) pull the spark lead off still keeps reving turn the fuell off and turn bike upside down so the fuell drains out of the carby and it finally stops .....phew

    i Thought it was the new HD trottle i got from SBP not disengaging properly (Not strong enough Spring in the carby) upgraded spring so it returns shut all the time and wd40'ed the twist handle so it turns smoothly......

    go out again go for a squirt about 10min come back and pop the clutch and it happens again.... bike does seem to struggle abit when i let go of the throttle kinda sounding like its dying

  2. motorpsycho

    motorpsycho Active Member

    it sounds like you either have a major air leak, your throttle slide is in wrong and it's binding up in the carb., or your throttle is cable is sticking.

    if you pull the spark plug wire off the engine should stop revving, but remember, it's probably spinning at 8000 rpms, so you have to give the piston time to stop moving after you pull the wire off. so it may sound like it's still revving, but it can't still be revving up at that point because it's impossible for it to without spark.

    you say that you turn the bike upside down? well, doing this can cause the float in the carb to become out of adjustment beleive it or not. It can also cause the float to cock sideways in the bowl which would result in the carb flooding over.

    by the way, wd-40 is not a lubricant it's made to displace water.
  3. professor

    professor Active Member

    I suspect a stuck throttle slide like Motorpsyco said.
    This is what I would do- repeat the procedure to get the problem.
    Kill the engine by leaving the clutch engaged and stopping with the brakes, without touching the throtle / cable or carb top- remove the air cleaner and look inside the carb.
    If the slide is stuck, you will see it.
    Then gently pull up the cable out of the carb- if it seems loose- it is the slide, if tight- it's the cable or hand throttle.
  4. heyhey13

    heyhey13 New Member

    Thats what i think the problem is i'll have a good look this afternoon

    and BTW it is absolutely possible for the engine to keeps revving for a while after the plug wire is removed it's because the motor is moving at such high speed that the heat and compression make the combustion happen

    as it did for me it kept revving for at least a min
  5. motorpsycho

    motorpsycho Active Member

    a minute is a long time for an engine to keep revving (as in building rpms) without a spark plug wire attached. gasoline will ignite from heat and compression, but i don't think these little motors have enough compression or enough heat to ignite gasoline. I could be wrong tho, but if your engine is hot enough to ignite unburned gas with out a spark, then you might be running it too lean.
    again, i could be wrong and this is just my poinion.
  6. HeadSmess

    HeadSmess Well-Known Member

    yep, if its hot enough or coked up enough or has a high enough compression to "diesel"...somethings wrong.

    weakness and hi revving is usually a lean condition.... air leak or blocked pilot jet.

    bet you just got that carb out the box and whacked it straight on? ALWAYS PULL THEM APART FIRST AND CLEAN THEM!

    if your killswitch isnt working.... um... fix it!

    and to kill it? you went to all that effort without thinking "why not just dump clutch and stall it?"... yeah, ok...panic sets in, i know, i know...i was the same way when my lathe grabbed my shirt....forgot all about the brake! until i was pulled down onto it... oh! i said...oops. then tucked in what was left of the shirt :)

    next time just stall it or pull the plug lead :)
  7. HeadSmess

    HeadSmess Well-Known Member

    im asssuming you changed carbs... HD throttle?

    if not...clarify!
  8. heyhey13

    heyhey13 New Member

    you miss understand the kill switch works but it will not work if the motor is running at too high a speed and you didn't read i did pull the plug lead it was going so fast it didn't matter:snobby:

    and the reason i stooped riding was because my chain fell off so the engine revved its little head off so dumping the clutch would have done jack and probably damaged my freewheel
  9. heyhey13

    heyhey13 New Member

    All fixed it was a lean condition moved the needle down a notch seems to be ok
  10. heyhey13

    heyhey13 New Member

    it is a billet aluminum throttle from Sick Bike parts better that that cheap plastic one
    And no carbie change well not yet
  11. motorpsycho

    motorpsycho Active Member

    Hmmm, so I do seem to know what I'm talking about. One of the the first things I said was that it sounds like it's running too lean.
    But seriously...moving the needle down one notch will not make THAT much of a difference. To go from the engine being so lean that it's revving out of control to running fine just by moving the needle down, seems unlikely.
    And (by reading exactly what you wrote) "moved the needle down one notch"...this would actually make it leaner. You need to raise the needle to richen it up. but I think what you meant was that you lowered the "E" clip which would raise the needle.

    I don't want to sound like a know it all, but this just sounds too good to be true in my opinion. Making a simple adjustment to the needle should not have fixed the problem that fast. Unless there was something blocking the jet and by luck, it fell out when you were messing with the needle.

    But if you say that it fixed it, it must have....but I still think there's more to fixing the problem than just re-adjusting the needle.

    Again, just my opinion.
  12. heyhey13

    heyhey13 New Member

    Well in the process i adjusted the cable and re did all the intake and lower crank gasket

    My theory is that while riding the bike some fuel has split down the intake and settled in the crank and when i pulled the clutch it revved uncontrollably thats why it only did it when i went for a ride and not in the shed testing it out

    Thank you for all your input it has helped me to figure it out quickly :idea:

  13. keatonx

    keatonx Member

    My little 31cc does this too. If it gets lean, it revs in idle. And if i give it gas, it dies because it can't rev any higher. Check the plug.