Coil quit...or maybe something else

So i unload at the hillclimbs saturday, warm the bike up and get ready to ride, put it in gear and it dies. Start it up and try again, it dies. Start again and it runs super crappy, then refuses to start. I pull and replace the plug, no spark, check, clean and reconnect all connections, nothing. I am assuming its the coil, any thoughts?


Its a 2001 cr500 af if it matters

Edited by ddewey78

Did you try a brand new spark plug? if not, do that first. If a bike is warmed up at low rpm for too long, it will foul the plug and no amount of cleaning it will fix it.


You did good by checking all the connections- sometimes if a connector comes loose in the ignition system, it will create the exact problem you are having.


Then, make sure the spark plug cap is properly installed onto the spark plug wire/coil. The spark plug cap has a screw in it with very small threads that screws onto the spark plug wire. Make sure that it has not come loose. standard threads = righty tighty :)


If that doesnt fix it, make sure your engine kill switch on the handlebar is not the problem. A stuck kill switch (ground to stop system) prevents the coil from firing. Unplug the two bullet connectors that are located right near the steering stem (follow the wires from the kill switch down until you find the 2 connectors).


If you still cannot get spark at the spark plug, get your multimeter out and check the resistance for the coil and stator. Check the factory service manual to see what the correct resistance values are.  The ignition control module cannot be checked. If the igntion coil checks out fine and the stator checks out fine, then the igntion control module could be the problem. There are weird situations where a stator may check out ok but still does not work properly..... :)  I doubt you will get to that point but just be aware it is a possibility.

this may help you as well....... (from the factory manual)



Yup, tried a brand new plug, the kill switch was unplugged. I didn't have a multi meter on me so I couldn't check those things. Ill check them after work today. Coil will be here Wednesday because I ordered it immediately when I got home, before thinking it could be the stator or CDI

nice- you are on the right track.


my 1996 CR250 coil failed on the trail, 5 miles from the truck, about 2 months ago-  The bike would idle and run at low rpm with less than half throttle but full throttle or above 5000 rpm, the bike would bog out like you were pressing the kill switch. I had to nurse it back to the truck; im so glad I made it back.


I checked everything and the primary side of the coil showed twice the resistance that it should have had.  I went to buy a coil, but it had been discontinued.  I used a coil off of a 2001 CR250 and now it runs properly.


The coil usually fails first, then the stator, then the ICM/CDI.

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