we have the same problem with a 85 225 dx atc, and i couldn't figure it out for the longest time. Then i changed the spark plug and the problem was solved. I also changed the stator, cdi and coil before coming to this $2.25 solution!! not happy!

 

well i replaced the stator and it fired up on the first try with the electric start. thank god.

 

great glad to hear it.