66cc suddenly lost power

Discussion in '2-Stroke Engines' started by chancecube, May 1, 2011.

  1. chancecube

    chancecube Member

    i was out for a ride and about 30 miles in my bike started what sounded like 4 stroking. could only go about 10-15 and wouldn't run up hill. i switched out parts one at a time to narrow down why it went south. i switched out the carb, the spark plug, the cdi and even emptied the tank and remixed new fuel all with no change. there's about 200 miles on the motor. any ideas?
     

  2. chancecube

    chancecube Member

    ok i changed out the magneto and it wouldn't start at all so i switched back the the original magneto and it now it wont start at all. i have no idea why it wont start
     
  3. motorpsycho

    motorpsycho Active Member

    have you checked all of your wiring connections?
    did you use the kit supplied push together wire connectors?
    if so, those connectors are junk and they will break and vibrate loose. I would suggest soldering all wire connections and get rid of those connectors (if you haven't done that already).
    another thing is that if you have anything hooked to the white wire (like a headlight) disconnect it and try to start the motor. also check to make sure that none of your wires have rubbed through the insulation and have bare wire touching the frame or anything else.
    is there spark at the spark plug?
    is there gas flowing into the carb?
    if you have spark, spray a small amount of starting fluid into the throat of the carb and try to start it.
    if it fires, then you have a fuel delivery issue.
    check to make sure that your float is not stuck in the up position keeping the needle and seat closed. this will not allow any fuel to get into the float bowl.
     
  4. chancecube

    chancecube Member

    all wires are good. i am getting spark. i have 2 carbs an nt and cns both doing the same thing. i will try some starter fluid to see it it turns over any.
     
  5. GearNut

    GearNut Active Member

    Key missing from the mag rotor and the rotor slipped on the crankshaft?
     
  6. chancecube

    chancecube Member

    the mag looks fine and turns fine the rubber seal under it appears to be ok. should i take off the mag and examine the mag better?
     
  7. chancecube

    chancecube Member

    i think i found out what was wrong. the first picture is the piston at its lowest point. doesnt come down far enough to even see the top ring. the second picture is the piston at its highest point. so high you can see the bottom of the piston and underneath the piston. this cant be right. and prolly why im not getting any gas.
     

    Attached Files:

  8. motorpsycho

    motorpsycho Active Member

    well I'm pretty sure that's not the problem. The gas-oil mix is taken in under the piston where it lubes the bearings, and then it gets forced up into the cylinder though a port. (Someone please correct me if i'm wrong here).
    if this was the problem, your engine would have never ran.
    piston position can't just change without having a major mechaincal failure.
    if you are thinking that the piston moved or is not going down far enough anymore, the engine wouldn't even turn over.
     
  9. chancecube

    chancecube Member

    i have another motor and its piston goes well below the carb port (picture below) and doesnt go high enough to see the bottom of the piston like the motor pictured above
     

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  10. motorpsycho

    motorpsycho Active Member

    hmmmmmmm. I have no idea
     
  11. GearNut

    GearNut Active Member

    You have the cylinder installed on the engine up-side down. That is giving you a wrong impression of how they work. The top of the piston on these little engines should never, ever uncover the intake/ manifold port. They do not have a boost port like a modern 2-stroke motorcycle.
    Although this animation shows the intake and exhaust on the same side of the cylinder, the action of how it works is identical to these little Chinese piston port engines. The Chinese engine has the exhaust on the more traditional, other side of the cylinder and the transfer ports are on the sides of the cylinder is all the difference.
    http://library.thinkquest.org/C006011/english/sites/2_taktmotor.php3?v=2
     
    Last edited: May 2, 2011
  12. chancecube

    chancecube Member

    so the fuel oil mixture drops down into the motor and is forced back up through the ports. well **** i dont know whats wrong with my motor, i still havent tried the starter fluid. i gotta go get some.
     
  13. chancecube

    chancecube Member

    show you guys what im working with. i would really like to get it fixed. nice weather is here.
     

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  14. GearNut

    GearNut Active Member

    WD40 makes for a good starting fluid for 2-stroke engines. Very flammable and oil for lubricating all in one spray can.
     
  15. GearNut

    GearNut Active Member

    A 2-stroke engine needs the following to run well:
    1. Fuel and air mixed at the correct ratio by a well working and tuned carburetor.
    2. No intake, exhaust or crankcase leaks.
    3. Good compression in the combustion chamber.
    4. Good, strong spark ignition timed to happen at the correct moment in relation to the position of the flywheels (wiring problems are most common).
    5. An exhaust that is not plugged up.

    Anything wrong with any of the above can make a 2-stroke engine run poorly or not at all.
    Check each and every issue carefully and you will find the problem.
     
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