have to ride today, checked all grounds on my 250r, no spark, tried 4 different plugs. this might be a dumb question but will a 400ex coil switch out? probably not im guessing

 

Last time I had the same problem on my R it turned out to be the Boot. I replaced the plug boot and she fired right up.

 

check all your butt plugs wiring conectors did it just all of a sudden do this ? you can check the mag assy and the impulse coil with a ohm meter i dont know the specs but if impulse coil has zip then its impulse coil now the CDI could be the dont know of a tester for them

also check your kill switch just unplug it to isolate the switch
good luck

 

I might be too late but I would change out the CDI unit, thats usually the cause.

 

check all the things everyone said and if theirs still no spark, pull the cover off the stator and see if water leaked in there.sand the tab and check the spark. i have an extra coil and cdi.

 

I had alot of problems with the stock kill switch assembly. Bypass it and see if that helps. I now have a simple bush botton kill switch from a XR on mine because of it.