Engine Trouble No start.. used to run fine.

Discussion in '2-Stroke Engines' started by wevie, Nov 16, 2014.

  1. wevie

    wevie New Member

    Greetings and salutations. First post here.

    My son drug home this 2-stroke bike this summer. He had it running and I guess it ran fine for quite some time. I personally never messed with it at this point.

    A couple weeks ago he asked me to order him a new CDI. He said he was just riding down the street and it died - wouldn't start - no spark.

    I checked it out. Magneto checked out good with ohm meter. New plug. No spark. I ordered a CDI from bike berry. It started and he rode it up the block and back. Now it won't start.

    This morning I helped him clean up the wiring and do some troubleshooting.

    1.) New spark plug. New spark plug wire. (had this stuff laying around so why not) We have a good blue spark at the plug.

    2.) Pulled carb. Removed bowl. Verified fuel in bowl. Needle/seat work fine.

    3.) Pulled magnet and verified the key was still in place.

    ***We have NOT tried to tow start it yet. Woke up to snowy roads.***

    The durn thing should start right up. Fresh mixed fuel. Have fuel in carb. Have good blue spark.

    Only thing is ever since he brought this home it has been operated without a muffler. There is just about 4" of pipe coming off the head and pointed down.

    Any guidance at all would be appreciated.


  2. butre

    butre Well-Known Member

    those carbs are notoriously leaky, make sure there isn't an air leak after the carb. also make sure there's no oil inside the clutch cover or the magneto cover as that would indicate blown crank seals
  3. crassius

    crassius Well-Known Member

    check compression, look for oil around seam between head & barrel, look for oil where barrel meets cases, look where butre said

    hopefully you don't have the dreaded 'good spark CDI at wrong timing' that is hard to test

    BTW, is the spark plug wet with fuel after trying to start it?
  4. wevie

    wevie New Member

    No oil leaks.

    What numbers should I see on a compression test?

    Spark plug is wet with fuel after trying to start it. I get a bit of smoke out the exhaust, but no audible clues to the motor trying to fire.
  5. crassius

    crassius Well-Known Member

    depending on motor, compression may be between 120 & 160

    smoke out the exhaust with no dripping could be timing gone bad - if dripping is present, it may just be an engine full of fuel from not turning off petcock when stopped
  6. Robot

    Robot New Member

    Well the worst of all possibilities, If the magneto points top dead center timing it is likely correct a broken connecting rod will throw out port timing before total failure repair or replace the crank a drill press would help in this case if that's no good get a new engine.. I've yet to totally disassemble one of these engines but they are easy to understand more or less. The engine is likely broken but you would know it for sure it will run poorly before it fails completely unless it stopped suddenly in which this is likely as well. You get a better engine by welding the crank anyway but that's my opinion..
    Last edited: Nov 21, 2014
  7. crassius

    crassius Well-Known Member

    I've often seen a bad CDI make a good spark that is at wrong time