Very Strange Engine Trouble

Discussion in '2-Stroke Engines' started by creede55, Oct 17, 2014.

  1. creede55

    creede55 New Member

    Howdy, I bought an engine kit, assembled it, and got it to run for about a week solid with no problems. Starting 3 days ago the engine started to get harder and harder to start but once I got it running it worked fine. Today the engine would not start at all. I drained and refilled the carburetor, check the spark plug for spark (tried a new spark plug to make sure there was enough spark), checked the timing on the magneto, checked the wiring, tightened down all the gaskets, tried starting with a lot of fuel in the carb, and fiddled with the choke. Still it will not run. The piston turns without effort and I can hear the engine turn over but no matter how hard I pedal it will not start.

    Has anyone else encountered a problem like this?
     

  2. piecepatrol99

    piecepatrol99 Member

    If you're using the stock ignition coil, they have a reputation for being a garbage part.
    Mine went bad. Though it was allowing voltage to pass to the plug (thus showing spark) the spark was too weak to fire the motor.
    I upgraded to the aftermarket coil and seperate ignition box from sickbikeparts.com

    Original coil lasted about 200miles spread over four years. The upgrade/replacement has 600+miles on it this summer.
    The only time I've had trouble starting it now have been issues with installing the motor in a new bike and adusting to new gear ratio at or behind the chainring(s).

    On a weird note: take apart your muffler to check for obstruction. Mud wasps started a hive in my tail pipe and blocked it off. The motor is too low compression to have blown it out.
     
  3. piecepatrol99

    piecepatrol99 Member

    Another issue I've heard mentioned is the main jet in the carb can come loose and fall into the fuel bowl. With an NT carb, the nut that holds the throttle cable to the carb can loosen too. Do you have a rubber washer in this fitting? It is another source for an intake leak. Though it is more likely to cause a high idle issue vs hard start.

    Hope this helps...
     
  4. creede55

    creede55 New Member

    I went out this morning and took the carb apart, everything was still tight and screwed in. I tried tightening the metal collar that connects the carb to the engine since I noticed the collar slid forward a bit leaving 4 1mm holes which could have been the problem all along. Got it all tightened and sealed up, still though, the engine wont start.
     
  5. Purple Haze

    Purple Haze Active Member

    You definitely have an ignition problem. Are you running the stock plug and plug wire? The end cap on the stock wire is notorious for failing. Get a good quality wire, they screw onto the cdi box, while you're there, get an NGK B6HS plug and install. I think this will solve your problem. If not, check your wiring connections, you're not using the stock cheapazz connectors, right? Could also be the kill switch, the have a poor reputation for failure.
     
  6. crassius

    crassius Well-Known Member

    how's the compression? could be head gasket or case gasket leaking, could be a seal leaking

    are you sure the carb is seated so that you feel it hit metal when you push it onto the intake?
     
  7. piecepatrol99

    piecepatrol99 Member



    Do you have a multimeter? Check the magneto loop and ignition coil for resistance values.
    If the black to blue reads less than 33ohms, your coil is bad. Its letting voltage pass through which will show spark. But its no building a charge to actually fire the motor.
    Remove the spark plug and connect the volt meter to the loop. Turn the motor using the back wheel. Volt reading should be about 6volts.

    These tests will confirm which part is bad and needs to be replaced, short of the plug being broken inside the porcelan...
     
  8. creede55

    creede55 New Member

    Thanks for the replies and advice. I put in an order for a new CDI and hopefully that will fix the problem, if it does then when I get the money I'll invest in better parts so my bike doesn't crap out on me again.
     
  9. piecepatrol99

    piecepatrol99 Member

    Did you test the loop and the CDI with an ohms meter?
    I've forgotten the exact specs you should get but if you shoot an email to sickbikeparts.com or try looking for a vid on youtube, you'll get the info you need to confirm or dispell those components as the source of your problem.
    Replacing the loop or stock CDI are relatively inexpensive but why throw good money after bad chasing a ghost...
     
  10. Fabian

    Fabian Well-Known Member

    The Jaguar CDI and coil is a "must have item" on any motorised bicycle engine.
    If the bike still misfires after installing the Jaguar CDI and coil, you will most likely find that you have a bad stator coil, otherwise known as a magneto coil. Having said that, i have only had one stator coil fail on me in 5 years.
     
  11. jaguar

    jaguar Well-Known Member

    I agree with Fabian, and not because of financial interests but because it's true. The stock CDI craps out easily and has too advanced timing, especially if you increase the compression and put a better carb on, and especially if you port the engine for higher speed.
    Unfortunately the stator coil craps out easily too and you should always have a spare on hand. But some people replace them without realizing the problem was bad metal to metal contact at the coil mounting screws which serve as part of the ground path.
     
  12. creede55

    creede55 New Member

  13. piecepatrol99

    piecepatrol99 Member

    this is the coil I upgraded to when my stock CDI crapped out in less than 200miles.
    the new coil has 500+ on it and counting...
    I don't joy ride either. when I fired it up, its going to run no less than 26miles round trip for the day. up to 90miles for the day depending on where I have to go.
     
  14. Fabian

    Fabian Well-Known Member

    The Jaguar CDI has adjustable ignition curves, which is an important feature, especially if you are going to use a higher compression cylinder head and/or different types of fuel.

    The ignition key is relatively pointless because it's another component in the electrical system that's waiting to fail, and should you lose your key, you won't be going anywhere, and as we all know you "WILL" (at some point) lose your key; when you desperately need to use your bike.
    Secondly, the lightning CDI doesn't have adjustable ignition curves, which doesn't make it much different from the standard CDI.

    You are better off spending money on a decent bike lock if you are so concerned about your bike being stolen.

    There is no significant difference in performance between aftermarket CDI's and the standard CDI, going from my experience, however the Jaguar CDI (from my experience) dramatically improves engine life, compared to the standard CDI.

    If you want a noticeably smoother engine (at the expense of slightly lower engine power) you can adjust the Jaguar Ignition curve to the lowest setting.
     
    Last edited: Oct 21, 2014
  15. jaguar

    jaguar Well-Known Member

    click on my signature link to learn more about the Jaguar CDI (now called the Performance CDI) and other options for upgrading these engines
     
  16. creede55

    creede55 New Member

    Well, turns out my coil was broken and the new one works. I checked it with a multimeter and got zapped pretty bad when I held the spark plug and turned the tire. I put everything back together and the engine still won't start. I did notice that if I hold the spark plug by the wire I won't get a spark, but if I hold onto it or hold it on the frame of my bike a get a very consistent and visible spark. So now I'm thinking something went wrong in the wiring, or possibly in the kill switch. What do y'all think?

    I have my wires set up like they were before - blue to blue, black to black, the yellow wire from the kill switch connected to the blue wire, and the black wire from the kill switch connected to a screw on my bike frame.
     
    Last edited: Oct 28, 2014
  17. piecepatrol99

    piecepatrol99 Member

    I've got blue to blue and black to black from loop to coil. My yellow from the kill switch goes to the front motor mount. Green from the switch to blue between the loop and coil.
    Doesn't sound as though it should make a difference with the kill switch being a momentary connection.
    You may be right on the bad switch idea...
     
  18. piecepatrol99

    piecepatrol99 Member

    I reread your post... you mention a dfference when holding it by the wire.

    Is the connector at the top of the boot fully engaging the top of the plug? Has it stretched or worn from instalation and removal? Is the wire broken inside the insulation?
    It may arcing some where before it gets to the plug...
     
  19. jaguar

    jaguar Well-Known Member

    when you say your coil was broken you don't say if it was the high voltage coil or the stator coil.
    not allowing the spark a return path via the frame of course would prevent its occurrence and does not indicate anything is wrong
     
  20. MotorMac

    MotorMac Member

    Disconnect ( cut ) the yellow and green wires from the kill switch and see if it starts.
     
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