Engine won't start anymore

Discussion in '2-Stroke Engines' started by Canon, Apr 15, 2011.

  1. Canon

    Canon New Member

    There is no spark, I tried to test the spark plug by keeping it plugged into the cdi but sitting on top rather than outside of the actual engine, and pedaling with the back wheel up. I got no visible spark so I'm assuming the plug is bad, but also every time I try to tow start it i pull the plug and its all black and oily as is the spark plug hole. Will a new ngk plug fix this?

  2. GearNut

    GearNut Active Member

    It could be a number of things. You have to diagnose the ignition system as a whole unit.
    1. Bad kill button, stuck in the closed position internally.
    2. Bad connections between the engine and CDI box. The factory connectors are notoriously horrible. You need to cut the factory connectors off, strip the wires and solder each connection together and seal them with heat shrink tubing.
    3. Bad spark plug wire. They are known to fail at either end as well as randomly in the middle. They screw into the CDI box and into the spark plug cap.
    Best fix it to use an automotive wire or get a good NGK wire from a vendor. Either one has a good quality spark plug cap as well. Depending on the type you may need the threaded nipple on the end of the spark plug to allow the spark plug cap to snap on to the spark plug.
    4. Bad spark plug cap. The factory ones are notoriously poor in quality.
    5. Bad spark plug. The factory ones are not reliable. Some folks get 500 miles out of one, some get 5 feet out of one.
    6. Bad solder connection on the Magneto in the engine. These solder connections tend to be "cold" soldered from the factory. A cold solder joint will look to be good visually but in reality it is bad. The black ground wire that attaches to the frame of the magneto is the most common culprit. The blue and white ones are less so, but there has been problems reported on them too.

    The remedy is to unsolder the wire from the connection, clean the wires on both ends of the connection well, (Use a green scrubby pad and alcohol. Not drug store alcohol, not Jack Daniels either. Use 100% denatured alcohol from a hardware store) and re-solder the connection back together. Get the wires hot enough to melt the solder. Do not melt the solder on the soldering iron and flow it onto the connection. That is a cold solder joint when the wires themselves are not hot enough to melt the solder. Be careful to not overheat the wires though or you can melt the insulation.

    That should get you started on your way to repairing your ignition system.
    Good luck!
    Last edited: Apr 15, 2011
  3. Al.Fisherman

    Al.Fisherman Active Member

    Also check the magneto, for proper alignment.

    Last edited: Apr 16, 2011
  4. Canon

    Canon New Member

    It was the magneto. luckily I had a spare one in an old scrap engine that works perfectly. Now that thats fixed maybe you guys could help me with my current problem, the engine will only start with the choke up all the way. Once started I can slowly lower the choke as I increase speed, but if I do it too quickly the engine bogs down when I roll the throttle. I have adjusted the carb pin to both the highest and then lowest setting, but it still bogs down at low speeds. I have an expansion chamber and read that I might need a new jet. I haven't done a proper plug chop yet since I dont have a kill switch, but everytime I pull the plug its black and oily. Do I need a new jet? If so what size?
  5. retromike3

    retromike3 Member

    too much gas

    Sounds like you are getting too much gas. I would try moving the clip up one notch. I replaced my new carb with one I had used on a old motor because it was using way too much gas. The reason for these bikes is that you should get really good milage.

    It usually takes me about a mile or two before I can let the choke off all the way. Until then it does tend to bog a bit.

  6. GearNut

    GearNut Active Member

    With a black spark plug, it sounds like too rich to me. The jet size you will need depends on where you live (altitude), the expansion chamber you are running as well as what your particular engine wants. No 2 engines are identical, not 1 jet size is a fix all for them.
  7. Canon

    Canon New Member

    Well I'm in Charleston, SC so I'm at no more than 20ft above sea level. I use an expansion chamber from sbp and my engine is 66cc. I bought a new air filter from sbp and now It sounds like it can't idle fast enough. Even when I turn the idle screw all the way the engine can't maintain an idle at the same choke level I ride it on. I can kick start it by lifting the bike when the choke is all the way up but it dies after a few seconds, when I pull the clutch, or when I try to turn down the choke at all. Once I get going I can slowly turn down the choke to get faster and faster, but when I come to a stop and then try to accelerate it bogs down unless I turn the choke back up.
  8. GearNut

    GearNut Active Member

    It sounds like you definitely need a smaller jet.
    While I can tune nearly any motorcycle carburetor, I am not experienced enough with these carburetors to recommend a particular jet size for you to try.
    Ask SBP, I bet they can guide you very well. Or perhaps someone else here with more tuning experience with these carburetors will chime in.
    You can also do a search on this site for tuning info as well as soldering and drilling the jet you all ready have, a really low buck method that works awesome.
  9. Canon

    Canon New Member

    Thanks for the insight I just sent them an email.