Piston hitting spark plug

Discussion in '2-Stroke Engines' started by kcpoloman, Jan 12, 2009.

  1. kcpoloman

    kcpoloman Member

    I have an 80cc motor that I have about 80-100 miles on. I broke the motor in properly not getting into the throttle to much keeping the revs down and using proper gas/fuel mixtures. Worked great, no issues. But today I coudnt get it to start. I pulled the plug and it was closed, no gap. I regapped the plug stuck it back in and no luck. Pulled plug out again and it was closed again.

    Not sure why it would run fine the last month with no issues and all of a sudden it doesnt. Should I put another washer on the spark plug to pull it up in the cylinder a little higher? I pulled the head off and rotated the piston a few times and it doesnt appear that it is going that high. Looks like there should be clearance between the spark plug and piston.

    If anyone has any idea what I can do, please help me. Thanks in advance.

  2. try a new plug.... the center electrode may have come loose and is closing the gap.
  3. kcpoloman

    kcpoloman Member

    Okay, I'll go get a new one thanks for the tip.
  4. kcpoloman

    kcpoloman Member

    Yep, you were right. The electrode is slipping down. What do you recommend in a replacement spark plug?
  5. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    NGK B6HS Spark Plug for use in ambient temperatures of 80 to 110 degrees F

    NGK B5HS Spark Plug for use in ambient temperatures of 40 to 80 degrees F.
  6. Skyliner70cc

    Skyliner70cc Active Member

    Was this your stock Chinese plug that was hitting the piston? If so, another reason to support my belief that the stock plug is best used as a paper weight.

    Thanks for sharing your experience.
  7. kcpoloman

    kcpoloman Member

    I just picked up the NGK B5HS from the auto store. Thanks for the help everyone.
  8. kcpoloman

    kcpoloman Member

    I thought it was because everytime I pulled the plug out the gap was closed. But it turns out it was just the electrode sliding down when the spark plug was up side down. I was using the stock plug that came with the kit. That thing is probably better off as a paper weight. I didnt even get 100 miles out of that thing.
  9. Mountainman

    Mountainman Active Member

    piece of plug in the jug can do some damage

    the guys that sell these kits
    should replace those (defective) spark plug THINGS
    is there any good reason why they don't ???????????

    I think that this falls under MB suppliers -- MALPRACTICE issue

    a little broken off piece of plug in the jug can do some damage

    makes it hard to ride that THING
    Last edited: Jan 13, 2009
  10. kcpoloman

    kcpoloman Member

    Ya, I hear ya. I just invested in a NGK B5HS plug and she is up and running again. I feel alot better knowing I am using a quaility plug now. I would have switched a long time ago had I known what pos the stock plugs were. Again, thanks for all the help guys.