Engine Trouble First Bike/Motor - Low-power and runs rough

Discussion in '2-Stroke Engines' started by Servo, Jul 13, 2011.

  1. Servo

    Servo New Member

    I tried searching for my motor issue, but I didn't find what I was looking for. Honestly, it could be a lack of knowledge on my part.

    Here is what happened. I'm breaking in my 80cc, 2-cycle motor with a centrifugal clutch. It's still in the break-in period and on the first take of gas. I keep the rides short and the speed low. I studied up on the break-in.

    I was rolling down the street and it was running like usual. All of the sudden, I lost power and the engine started to run rough. By rough, I mean it ran normal and would vibrated hard, then back to normal, then vibrate hard. However, when I choke it, it runs smoothly.

    The motor still spins the back tire when I engage the clutch and hold the bike up myself. However, if I try to accelerate while riding its barely able to move. I can pedal up and the motor can maintain speed.

    Since the ride today that resulted in low-power, I only started it one more time. Thats how I figured out that it runs better choked. I only tinkered with the idle control to see if that helped, and it didn't.

    Any ideas?

  2. motorpsycho

    motorpsycho Active Member

    it's quite possible that you have developed an air leak where the carb mounts to the intake manifold.
    get yourself some starting fluid and with the engine running spray a SMALL amount where the carb goes onto the intake manifold. if the engine revs up on it;s own, you have an air leak.
    by running rough it could mean that the air-fuel ratio is beginning to get too lean (more air than gas) which would also result from an air leak.
    this can also be known as bogging, and when a 2 stoke starts boggig, they run teriible and have very low power and they sound really funny.
    something called 4 stroking can also occur when the air-fuel ratio is too rich, (too much fuel to air) so make sure that you have the choke turned off.
  3. Servo

    Servo New Member

    Thanks for the suggestion. I gave it a shot and it's not an airleak. I fixed the vibration problem, but I still have a lack of power but I should have been more specific. I have a lack of power to the wheel. The motor revs just like it did before, however, the acceleration is crappy. Could the clutch have died out already?
  4. motorpsycho

    motorpsycho Active Member

    it sounds like your clutch is out of adjustment and is slipping.
    you will have to play with the clutch arm and adjust the cable (on the left side of the engine). i doubt that the clutch is gone already.
    if adjusting the cable at the arm doesn't help, you may have to go in under the right side cover and adjust the flower nut on the center of the clutch. there should be a post here describing how to do it.
  5. Servo

    Servo New Member

    Thank you so much for the advice!
  6. Servo

    Servo New Member

    Okay, I was out of town and have been tinkering.

    I've found that the clutch is doing really well. I've eliminated the vibration so thats not a problem anymore.

    The engine seems to run fine and rev up normally. For some reason, the power just isn't being translated to the wheel.
  7. motorpsycho

    motorpsycho Active Member

    so it sounds like the clutch is slipping?
    does the engine rev up freely and really fast when you try to ride?
    or, is the engine struggling to rev up like it's having a hard time pulling the load?
  8. HeadSmess

    HeadSmess Well-Known Member

    um. centrifugal clutch? is this a friction drive thing or a ht?

    this is where a picture is worth twenty million thousand words....
  9. motorpsycho

    motorpsycho Active Member

    oh, centrifugal clutch.....that could be the whole problem.
  10. Servo

    Servo New Member

    Well, the engine revs freely and easily. When I try to ride it is some VERY slight acceleration. The whole thing happened very suddenly on a ride. I had normal acceleration and then BAM, almost nothing.

    So, does this mean I'd have to completely replace something or the engine?
  11. motorpsycho

    motorpsycho Active Member

    sounds like the clutch is toast or way out of adjustment.
    I'm not sure how to go about adjusting a centrifugal clutch and it may not even be possible to adjust one...I have no idea.
  12. Lazieboy

    Lazieboy Member

    So what was the vibration issue, and the fix.
  13. HeadSmess

    HeadSmess Well-Known Member

    it could be the clutch, depending what brand it is...if its maxtorque, definitely! i had one of them die within a week!

    lets seeee, it vibrated like mad, then smoothed out at certain times, seemed to be a matter of luck. things that arent lined up well and spin at 6000rpm tend to vibrate badly.

    it always drove though :)

    you still didnt say if its friction drive or chain drive or give us a pic so....

    im going! :jester:

    (it could just be one of the clutch shoes has spat its lining and there goes the balance...and the drive...what sort of noises is it making?)