Bike engine skipping, not as powerful

Discussion in '2-Stroke Engines' started by ShiFuBill, May 2, 2009.

  1. ShiFuBill

    ShiFuBill New Member

    Hi, I'm having some trouble with my bike. It was running fine, but I noticed there was an oil leak. The muffler wasn't on well and oil was leaking out. It didn't fit quite right because the muffler was against the frame. I cut
    a piece of cardboard (very thin) in the shape of the piece that is fitted between the muffler and the engine and fitted the cardboard between this piece and the engine. This fixed the lead, however there is another problem that may or may not be related.
    When I'm running engine, it runs smoothly for a while, but then feels like it pulls back every few seconds. Like it's missing, or skipping or something.
    Also, it seems like it isn't getting as much power as it used to. I'm not sure because I didn't run it for a while, but seems like it's just not going as fast as it had been. I'm not sure if the fix I mentioned above has anything to do with it, it doesn't seem that that would do anything, but I thought I'd mention it.
    Another issue is that I also added a new tension piece (that piece that adds tention to the chain from the engine). Could it be that it has too much/little tension?
    I've adjusted the carbourator adjustment screw and the air intake lever, but I'm not sure if I'm helping it.
    Also, since I added the cardboard piece it seems to be running quieter. I don't know if that's a symptom or a benefit.
    Any ideas?

    Thanks!!!
     
    Last edited: May 2, 2009

  2. arceeguy

    arceeguy Active Member

    Sounds like the engine may be running a little too rich. As things warm up from winter to spring/summer, the jet needle may need to be adjusted. In this case, raise the clip a notch to lower the jet needle and lean the mixture a little.
     
  3. ShiFuBill

    ShiFuBill New Member

    Interesting. What's the jet needle and what's the clip? And how do I adjust them?
     
    Last edited: May 2, 2009
  4. arceeguy

    arceeguy Active Member

  5. ShiFuBill

    ShiFuBill New Member

    Well, there was nothing about a jet needle or a clip, but I think you meet the part that regulates how much fuel enters the chamber. As I understand it, turning the throttle makes more fuel go in, so if it needs to be more lean wouldn't you just not turn the throttle as much, and wouldn't that make it even less powerful?
     
  6. gerichardson

    gerichardson New Member

    Too much Too little chain tension

    ShiFulBill,

    Your chain should have some play. Roll your bike a bit and take a ruler to measure the movement. An inch or so is okay. That's what I have.
    The chain shouldn't be tight with no play. Check the forum for more specifics on the best adjustments.

    Ride on!
     
  7. arceeguy

    arceeguy Active Member

    Whoops sorry - go to the point where it says that "All Skyhawk GT kits come with throttle cable pre attached". The photos of the carb slide assembly are there. The jet needle is the brass needle that moves up and down with the slide. There is a circlip that adjusts the level of the needle.
     
    Last edited: May 2, 2009
  8. ShiFuBill

    ShiFuBill New Member

    Once again, I think that this just regulates how much fuel is coming into the chamber. I can understand how this would affect it when the engine was idling, but not how it runs.
     
  9. ShiFuBill

    ShiFuBill New Member

    There is another thing I forgot to mention. It doesn't start as quickly as it used to. It seems to pull without firing for a second before it begins to start. It feels like it's dragging or something.
     
  10. arceeguy

    arceeguy Active Member

    The jet needle controls idle mixture to about 3/4 throttle, that's when the main jet comes into play. Some folks have posted that their engines run too lean with the stock main jet and some post that they run too rich. It all depends on your operating conditions and the phase of the moon when your carb was manufactured. :D Is your engine "skipping" at part throttle or at full throttle?
     
  11. ShiFuBill

    ShiFuBill New Member

    I guess part throttle. I tested it just a few minutes ago. When it gets up a good speed it suddenly seems more powerful and no longer seems to be dragging or skipping. You said it controls the idle mixture, does that mean when the clutch is on or off? It's when the engine is moving the bike that the problem is. I thought idle meant it wasn't moving.
    Anyway, if I do need to adjust this thing, do I need to move it up or down?
     
  12. arceeguy

    arceeguy Active Member

    When it gets up to speed, it is the main metering jet that controls the mixture. (there is overlap from the needle jet)

    You want to raise the clip one notch, this will lower the needle (note that it is slightly tapered) and that will lean the mixture a little. You may need to adjust the throttle stop screw (idle speed) after you adjust the jet needle. The idle will probably go up.


    Most of these engines tend to run a bit rich at part throttle, but it shouldn't be too "slobbery rich".
     
  13. Junster

    Junster Member

    Check the Intake also. You might have developed an air leak. Try a few squirts of wd-40 at the cylinder where the intake attaches and where the carb connects to the intake when the engine is running. Listen for the rpm to change. Also check the head bolts and around the base of the cylinder. If my carb comes even slightly loose when I'm riding I can tell right away.
     
  14. ShiFuBill

    ShiFuBill New Member

    What's the idle stop screw and adjust it how? Sorry but I'm not up on all the terms yet.
     
  15. crazeehorse

    crazeehorse Member

    thats the small screw sticking out of the left side of the carb,beside the primer button. turn it clockwise to increase the idle speed. turn about a 1/4 turn at a time till your get your desired idle rpm's.
     
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