Motor dies after intial warm-up...help??

Discussion in 'Motorized Bicycle General Discussion' started by DoubleUgly, Apr 14, 2012.

  1. DoubleUgly

    DoubleUgly New Member

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    I am stumped.... any assistance or suggestions are most appreciated!!

    Heres what I have:
    A 5 year old 80cc. 2 stroke china engine. Roughly 400 miles on engine.


    What the issue is:
    After the intial 2 minute warm-up, the engine will stutter, then completly die. Will not fire untill after after a 2-3 minute period, then will run for 30 seconds...then die suddenly.

    What I have replaced:
    Magneto, carb, CDI and spark plug, and intake gasket on carb....all new parts.


    Should I be looking deeper? Maybe a blown gasket on the lower end of the engine. This engine has given me no issues at all... then suddenly, it doesn't like me ;)

    Thank you for any ideas that may come my way. Please let me know if more information is needed.
     
  2. GearNut

    GearNut Active Member

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    Welcome to the forum! You should introduce yourself so we can get to know you a little. Click me!

    Hmmm.... bad fuel delivery could cause that. The engine runs long enough to use up the fuel in the float bowl and then starves and dies. After 2 minutes the float bowl gets refilled enough for the process to repeat.
    A partially clogged fuel valve? Also could be the fuel valve screen that fits up inside the fuel tank. Said screen should be discarded anyways and an in line fuel filter used instead like this one: Click for link to filter example.
    What type of carb do you have? Some have a fuel valve on the side of them that can clog up just as easily as the fuel tank valve.

    If you have no fuel filter at all, there also could be junk blocking the fuel inlet in the carb too.

    A fuel tank cap that does not vent properly will cause that too. No air in = no fuel out.
    Slow air in = slow fuel out.
     
    #2 GearNut, Apr 14, 2012
    Last edited: Apr 14, 2012
  3. rustycase

    rustycase Gutter Rider

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    those were my thoughts exactly!
    rc
     
  4. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    Did you take the choke off after warm-up?
     
  5. 2door

    2door Moderator
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    All good advice you've been offered. Let us know if it helps.

    Tom
     
  6. mapbike

    mapbike Active Member

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    Yep, sounds like fuel delivery issue.

    One other thing that has caused a few people headaches also is the kill switch, probably not an issue with yours but I'd sure cover all the bases and be sure it's in good working order and not grounding on occasion from vibration or something.

    Best wishes, hope you get them wrinkles ironed out soon.

    Map
     
  7. DoubleUgly

    DoubleUgly New Member

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    Thank you all for the great feedback! I did get a few spare moments (from a bathroom remodel) to empty the gas tank and inside fuel filter. The filter did have some debris trapped. Approx. 10% covered with crud. Do you think this is enough debris to cause issues? I will order an inline filter as Gearnut suggested before I reinstall.

    I will also take the suggestion to introduce myself. I am from the Midwest, Chicago to be specific, and have had my motorized Schwinn Jaquar for 5 years. Love the think to death, not many motorized bikes up here in Chicago, so I do get the "Looks" from envious bystanders ;).

    I will also troubleshoot the killswitch. Will let you all know how much luck I have.

    Thanks again for all the great advice, and I am proud that there is a community of likeminded bike enthusiast, so give a helping hand.
     
  8. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    I'd try running it with the gas cap loosened first.
     
  9. GearNut

    GearNut Active Member

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    Pay close attention to the direction of flow arrow on the side of the fuel filter. If you install it to flow the other way it will still work but clog up alot faster. They are cleanable and re useable by the way. Just flush out the junk by flowing fuel backwards through it and re-install.
     

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