Spark or fuel?!?

3 replies to this topic
  • DrDeuceman

Posted January 12, 2008 - 08:58 AM


(this is 2001 YZ426)ok last saturday after a good 22miles of single tracks and open aryos we were on our way back to the truck when my bike just shut off like if i had hit the kill switch, while just sitting at idle while we were stopped waiting for a friend. i kicked it countless times and acted if it had no spark. we towed the bike out.

after about a day of sitting i gave it two kicks and it fired right up ran for about 3mins or so and died like hitting the kill switch. i have gone throught the top end (about 10-13 rides ago) on the bike and it has great compression. cams are in proper timing. so after siting for a little while the bike will start run for minute or 2 and die. ive checked the spark with and inductive pick up timing light, the old fashion pull the plug wire out connect the plug ground it and kick it over. no spark. ive Ohm the coil, cdi magneto, neutral switch, and kill switch. all ohm to spec. i found the light blue wire(from the neutral switch) cut and taped(looks like it has been like that for a while) although it had nothing to do with the running of the bike(connected or disconnected). i also have pulled the carb and set the foat lv(wasnt far off) and clean the jets out, no change same problem. now ive tryed a different coil and cdi black box from an 2001 wr426 and same problem.

next steps is to start tracing the wires in the harness its self to search for any shorts to ground and also pulling the cover to the cdi magneto to check for any thing loose. im banging my head on the wall with this one. any help, tips, and ideas are more than welcome PLEASE! i just wanna ride(dont we all)

Thanks, D Man :banghead:

  • grayracer513

Posted January 12, 2008 - 09:20 AM


Get it to shut down on you, and then quickly shut off the fuel tap and drop the center plug out of the float bowl (careful of fire). Observe how much fuel comes out. Turn the tap on with the bowl open. Does the flow seem normal?

If you are going to find a fault with the electricals with an intermittent condition like this, it will need to be in a failed state when tested, so again, get the bike to quit, then test the stator and signal coils while it's down. Also test for output voltage as appropriate. The problem is probably in the ignition coil or stator, but it could be the CDI, too.

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  • scalejockey

Posted January 12, 2008 - 10:47 AM


The pulse coil will act like this when it's bad but normally it has to get hot first. Take ohm reading then take a hair dryer to each coil and re-check.

  • sirthumpalot

Posted January 12, 2008 - 04:39 PM


To add to the above, it's possible your kill switch is going bad or a wire leading to it is pinched. Next time it dies, unplug the kill switch and see if it fires right back up. Be careful, don't ride it without a working kill switch!

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