Engine dies when clutched, no idle.

Discussion in '2-Stroke Engines' started by john doe, Aug 12, 2014.

  1. john doe

    john doe New Member

    So, for some reason, when I grab the clutch to idle, the engine dies instantly. Like, from full spin to completely dead in about a second... Even if I keep the throttle open. Sometimes it will stay running if I open the throttle wide when clutching, but not usually.
    What strikes me as odd is that it otherwise runs fine. Same acceleration, speed, power, and noise as usual. Until I grab that clutch.

    Engine is a 66cc HT with the stock carby and a rag mount drive.



  2. dougsr.874

    dougsr.874 Active Member

    Your post makes NO sense....How do you start the engine & pedal it with the clutch pulled in....?
  3. john doe

    john doe New Member

    You depress the clutch and start pedaling. Then you release the clutch and the bike starts.

    The bike then runs just fine until you grab the clutch again, at which point it dies instantly. Even with the throttle held open.

    So you kickstart it again.

    Again, it runs fine....

    Until you grab the clutch again. Then it dies. Again. Even when holding the throttle open (again).
  4. dougsr.874

    dougsr.874 Active Member

    Damndest problem I've ever heard....I can't fathom a correlation between pulling the clutch in & killing the engine....my only thought is that perhaps the clutch cable is somehow grounding out the kill switch wires....
    john doe likes this.
  5. john doe

    john doe New Member

    I'll have to do some inspecting but I have my doubts on that one. Possible, but seems... Eh.

    The only recent thing I've done other than basic maintenance and adjusting lately has been replacing the spark plug. But I doubt that's the problem since it ran fine with the new plug until the next day.
  6. crassius

    crassius Well-Known Member

    is the plug cap still in one piece?
  7. KCvale

    KCvale Motorized Bicycle Vendor

    That simply has to be the clutch cable interfering with the ignition wiring somewhere.
    john doe likes this.
  8. john doe

    john doe New Member

    After further thought and intense staring, I've determined that doug and KC are probably right here. Now I just need to stop trying to handle this on my breaks at work hahaha.

    Thanks guys.
  9. john doe

    john doe New Member

    Yep, you were right on with that one, mates. I had used a decent amount of electrical tape to try and hold the cheap wire connections together better, but it just didn't stand up to the Arizona heat. The adhesive melted and one of the connections slipped out. It was contacting enough to give me spark as long as the rear wheel was still forcing the engine to turn. The fact that I ran the clutch cable, next to these wires probably didn't help.
    I should have figured it was, a) something stupid, and b) something electrical.
    I'm thinking of cutting the stock connections off, stripping the wires back a tad, and using nice automotive ones. Pretty easy modification and will probably hold up much, much better.
  10. KCvale

    KCvale Motorized Bicycle Vendor

    Glad that fixed you up, it was the only thing that made sense ;-}

    You are on the right track considering replacing the stock wiring, I re-wire all my 2-stroke builds with a 16g shielded wire pair from the magneto all the way to the CDI.

    Just cut the mag wires off and solder one end to the magneto lugs.
    NOTE: I use the new Skyhawk mags with no white wire, ground is the bottom tab, there is no 3rd ground tab.
    Also note the wire I use has a red and white wire not blue and black.
    Red is hot, white is ground.


    Then just tuck the wire up with the clutch cable all the way to the magneto.


    Stagger your wire cuts at the CDI and solder the kill button wire in with the mag wires and it leaves enough space to not use any e-Tape anywhere.


    Glue a cover cap on and your set, and you can even get fancy with a keylock switch in the CDI cover which basically just shorts the ignition like the kill button so it can't be started without the key.


    Use epoxy to glue the cover on if you put a switch in so it can't be defeated.

    One last tip...
    Get yourself an NGK 5944 (BPR7HIX) Iridium spark plug, they are perfect for our hot summer temps and all I use.