Popping, missing, backfiring

I'm about at wits end here guys. I've got a '00 426, basically stock. About three weeks ago during a race, it began popping, misfiring, and backfiring. The plug has heavy, dry, black carbon. The exhaust has a terrible smell and black smoke. The bike ran fine during practice, but shortly after the start of the first moto the symptoms began. The jetting was unchanged from practice.

I took the carb completely apart, cleaned it, and blew out all passages. I drained all the gas and put in fresh gas and a new plug. Took it for a ride, same problem. I checked resistances for all electrical components per the owners manual and all were right in the center of acceptable ranges. Plug cap resistance was also fine. The local dealer checked it with the Y1 tester (I think that's what they called it), and the coil tested bad. The pulse coil also appeared faulty, with only 30% output.

So, first I bought the new coil and another plug. Took it for a ride and thought everything was fine. After about 5-10 minutes, the problem was back. Went and bought a new stator assembly and another plug. Took it for a ride, and again after 5-10 minutes, the problem was back. About the only thing left is the CDI and I really don't want to thrown away any more money than I already have. HELP!!!!!!!!

[ November 04, 2001: Message edited by: motobob911 ]


It sure enuff sounds like yer CDI is bad, tho, doesn't it? I have a 2000, and haven't had that problem yet, but I know that it was a bigger problem with the 2001. Good luck, let us know what you find out!


CDI and other control modules often work when cold, and begin to fail when they warm up, via usage.

If you chill the unit after the bike begins to fail, and it returns to normal operating status, you have a bad CDI.

You can obtain some spray on freeze-it (or whatever they call it) at a local electronics store.


[ November 05, 2001: Message edited by: DaveJ ]

all these circuit testers are all well and good but there's evidence of a dozen electrical units being out of spec and yet when replaced the fault is still there.

i would clean out my kill switch, clean a few earths, crimp a coupla wires.

check the air valve on your fuel tank.


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