New build. Engine won't start. Any words of wisdom?

Discussion in 'General Questions' started by I need some help, Dec 16, 2014.

  1. I need some help

    I need some help New Member

    Hello everybody. I have built one of the motorized bikes using the standard 80/66 cc 2 stroke engine kits that seem to be popular. I put it together and it did not start. I switched out the kill switch but, it still would not start. I get spark to the plug when it is resting on the head of the engine, and the carburetor sends fuel to the engine when the clutch is engaged (I can hear and see it doing so). As soon as I put the spark plug into it's slot and tighten it, the carburetor no longer sounds like it is working and the engine won't turn over. I am in the break in period and am currently using a 16:1 ratio. The spark plug has been replaced. Do y'all have any advice?
    Last edited: Dec 17, 2014

  2. dougsr.874

    dougsr.874 Active Member

    Don't know what carb. pumps means......could be the clutch is not tight enough and engine is not turning over with the plug installed.....
  3. crassius

    crassius Well-Known Member

    first start can be hard sometimes - single-speed bikes are harder to get good turns of the motor - be sure motor is turning, then try choke a few times, then no choke - be sure carb slide is hitting bottom of carb (you should be able to hear it hit when you back off throttle) - don't adjust idle screw before first start as you can pull slide up a bit with the throttle grip to find a good starting opening
  4. bluegoatwoods

    bluegoatwoods Well-Known Member

    I have heard that sometimes a bad spark plug can spark in the open air, yet fail to spark under compression. It's probably a fairly rare occurrence. But for the price of a spark plug, testing this out with a spare plug would probably be worth your while.

    I'm guessing, though, that that's probably not the trouble. It is sounding like a fuel issue. I'm also confused about the term 'carburetor is pumping'.

    But maybe that's not important. Can you confirm that fuel is getting into that carburetor?

    If the answer is 'yes', then I'd start leaning toward the spark issue again.
  5. I need some help

    I need some help New Member

    To clarify: when I say "the carb pumps", I mean that with the spark plug resting on the engine, I can see and hear it sending the fuel to the engine. As soon as I place the spark plug back in, the carburetor no longer sounds like it is sending the fuel to the engine.
  6. crassius

    crassius Well-Known Member

    I'd guess your clutch is slipping & not turning the motor at all.

    look for 'clutch adjust' here
  7. Think i can help, 1 the clutch shouldnt have anything to do with sending fuel thats the carbi's job once the vacuum happens when she fires up, if you remove the intake manifold and push it along with clutch ingaged you will be able to see the piston moving and spark plug in, if its not moving properly straight away you will know its the clutch slipping and just needs to be tightned, thats what happend to me and then she fired up 1st go