motor wont start. please help

Discussion in '2-Stroke Engines' started by Juwalantz, Jun 10, 2011.

  1. Juwalantz

    Juwalantz New Member

    ok i was out riding when the bike started to spit and sputter a little bit and then died. i pulled the plug and cleaned it and the bike fired right back up for about 5 minutes then it died again. i went and bought a new plug and the motor still wont fire. i deffinately have good compresson, i know i have fuel, and i know i have spark, no cloggs in the air filter or nothing.oh ya and i disconected the killswitch and still no dice i have not checked resistance of the magneto, or coil yet, but im going to tomorrow. i figured i did not need to check them if i have spark, but i think i might have a weak spark. is that even possible anyone ever had to replace a coil or magneto even though they still had spark? let me know any thoughts. just for your info, this is a boy go fast 80 cc with the centifugal clutch and pull start. it has aproximately 150 miles on it.

  2. Al.Fisherman

    Al.Fisherman Active Member

    To me it sounds like fuel starvation, but you say it has fuel. What have you done to verify it has? Yes a weak current can cause a weak spark either from the magneto or CDI, or ignition wire/boot. You really seemed to do your homework as far as checking it out. If it was mine and since it is especially a pull start, I'd remove the air filter and give it a shot or two of either gas, throttle body cleaner, or starting fluid to the carb and pull the pull rope.
  3. cpuaid

    cpuaid Member

    Which carb were you using? Sounds like what my bike did with a high performance carb. My kit had less than 100 miles on it. It would start and run for 5 - 10 minutes then be impossible to start again even with starting fluid, which was weird if it was a carb problem. In case I was getting a weak spark or having intermittent electrical problems, I swapped out all of the electricals one at a time (no kill switch, CDI, Spark plug, Plug boot and wire, Magneto). Did notice dried rust residue in the magneto compartment which tells me water had gotten in there at some point (my bike was stored outside under a tarp). With the swapped magneto it started up intermittently but it still wouldn't run. Took the carb apart and had fuel in the bowl and float appeared to move freely, pin didn't appear to be sticking. Got tired of messing with it so swapped it out with an old stock carb and several squirts of starting fluid later she started right up again. Been running good ever since with swapped magneto and old stock carb.
  4. i had a cdi fired when it want to and i always sorder my conn's and i had a weak cdi fire blue without the plug but when i put the plug on it fired yellows/white i hope it helps
  5. parrformance

    parrformance New Member

    I had a cdi that gave a weak spark, I swapped it out the motor fired right up. will not return my calls :(
  6. graucho

    graucho Active Member

    I'm going with Al.Fisherman.

    Vaporlock? Tank's cap (venting) too tight restricting the flow. Starved for fuel.
    While you were fiddling with the plug a little gas trickled back into the carby's bowl.
    Then she fired back up after replacing the plug, until it starved for fuel again. Take the
    tiniest drill bit you can find and drill a pinhole through the top layer of the cap. Just my 2 cents worth.
  7. Juwalantz

    Juwalantz New Member

    Pretty shure i have fuel. When I built this bike my carb would not fit inside the frame so I attached a piece of clear hose between the carb and the motor so the carb fits just outside of the frame. The cool thing about this set up, is that it works great, always fired right up, and most of all I can see fuel entering the motor. I'm still betting on ignition problems. But thanks for the advice. I will try a little starting fluid or something and see if that helps. If it does then I will look over fuel system again.
  8. Juwalantz

    Juwalantz New Member

    Thanks for the replies. I know I'm not starved for fuel because I have a clear intake, and I can see gas entering the motor. I'm thinking cdi. I have heard of more than one person on this forum say that there cdi gave weak spark. And come to think of it, I tried to start the bike up a few times without the plug wire plugged into the spark plug. Oops. I guess this is supposed to damage the cdi. Also these things are just so damb cheap. I already have 150 miles on it. I'm going to test the cdi right now and see what she reads on a meter. I will post the results. Again thanks for the help. Oh ya just for ****s and giggles I might try a little starting fluid befor I go cutting my connections. They are all heat shinked and soldered nicely. I would hate to have to cut them and find out I didn't have to.