engine wont start!!

Discussion in 'Motorized Bicycle General Discussion' started by kolomootro, Aug 18, 2011.

  1. kolomootro

    kolomootro New Member

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    so i finally got all the parts together on my bike but the engine wont start.

    earlier,i was pedaling hard and trying to make it start,but i forgot about the primer so it didnt start.on the way back i hit a bump and the chain came off and broke,luckily it wasnt the one that came with the kit,so i still had that one to use.now i can pedal easily,so im riding towards my house,and then i realize the bike has no brakes so i almost crash into a tree!(i had removed the coaster brakes wheel cause the sprocket wouldnt go on it,so i am using a wheel from a 10 speed bike)

    READ HERE FOR PROBLEM:now i figure out how to prime and use the choke so i try to start it again,still nothing.i know it has spark cause i saw it the other day,not sure about fuel,but i put some drops of fuel in the cylinder and still nothing.
    so the only thing i can think of is an AIR LEAK.I noticed when i got the kit there were gaps between the head of the engine and where it attached to the rest of the engine.I CAN SEE THE HEAD BOLTS!!!.ALL of them.The head gasket isnt bieng pinched ,its just sitting there!
    Anyways ill try to put some pictures and hopefully someone can help me.
    in this picture you can see the gap ,especially on the right side.

    EDIT:I got it to start!!i held the throttle and it started,then i adjusted idle screw so now it idles too.
     

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    #1 kolomootro, Aug 18, 2011
    Last edited: Aug 19, 2011
  2. kolomootro

    kolomootro New Member

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    any suggestions?
     
  3. ddesens

    ddesens New Member

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    Without compression you cannot have combustion. There needs to be a good seal where the head meets the cylinder. Make sure its torqued down.
     
  4. The Busted Nut

    The Busted Nut New Member

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    Try a bit of Permatex Ultra Copper from Any Ace Hardware, Lows, or Homedepot. I Know for a fact that all Aces have it.
     
  5. GearNut

    GearNut Active Member

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    That gap is common due to the way the head is manufactured.
    The head is machined with a raised ring right at the edge of the cylinder that compresses the head gasket. This ring is what some folks sand off to raise the compression ratio.

    As for not starting, check the basics.

    Adequate fuel flow out of the fuel tank valve.

    Did you install an in line fuel filter between the fuel valve and carburetor which is highly recommended? Is it clogged? The fuel tanks are well known for having rust and debris in them straight from the factory.

    The carburetor, is it actually assembled correctly from the factory or did they leave the fuel jets loose and the float height adjusted incorrectly (both are common).

    If you have no inline fuel filter then rust and debris could also be clogging up the fuel jets.

    Air leaks. Have you read up on air leaks yet?
    It looks like you have an NT carburetor. They can have air leaks where they clamp onto the manifold. Also the gasket between the manifold and cylinder is known for being made of a horrible wanna-be gasket material that is very brittle. Get rid of it and make yourself a good quality gasket out of good quality gasket paper.
    The gasket surface of the manifold can also be curved or wavy which will not let any gasket seal no matter how high of a quality it is.

    You already said you have spark, but check for it again.
    Have you cut off the factory plug in connectors and soldered the wires together, insulating them with heat shrink tubing or electrical tape?

    Have you tried disconnecting the kill switch?

    In closing, have you read any of the the beginner's threads?
    They cover alot of the issues that these engines are known to have.
    Here's a good one to start with:
    http://motorbicycling.com/f30/guide-bicycle-motor-preparation-care-354.html
     
    #5 GearNut, Aug 18, 2011
    Last edited: Aug 18, 2011
  6. kolomootro

    kolomootro New Member

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    i never untorqued it and i have no torque wrench though.
     
  7. ddesens

    ddesens New Member

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    At this point just put a socket on em and see if there snugged up good.
     
  8. kolomootro

    kolomootro New Member

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