2001 yz426 running rough

My 426 is running terrible. The bike is sputterring (running rough)and it actually backfired when I shut it off the last time I took it out. The rpm's seem to surge while idling (rough,good,rough,good). It seems to get worse the longer the bike runs. I changed the plug and this really didn't help. Everything on the bike is stock (jetting, exhaust etc.) I have done the blue wire mod. The coil lead popped off of the plug cap when I was changing the plug. I put the coil lead back on and everything seems to be ok. I would think that it is a relatively simple problem based on the fact that this happened overnight. Took the bike out and it ran great, the next time I start it I have this. I'd appreciate any help.

You might have somthing in your carb. Take it off and clean it, it could just be a piece of grit in one of the jets. Welcome to TT!

Thanks, glad to be here.

I'm pulling the carb tonight.

My 426 is running terrible. The bike is sputterring (running rough)and it actually backfired when I shut it off the last time I took it out. The rpm's seem to surge while idling (rough,good,rough,good). It seems to get worse the longer the bike runs. I changed the plug and this really didn't help. Everything on the bike is stock (jetting, exhaust etc.) I have done the blue wire mod. The coil lead popped off of the plug cap when I was changing the plug. I put the coil lead back on and everything seems to be ok. I would think that it is a relatively simple problem based on the fact that this happened overnight. Took the bike out and it ran great, the next time I start it I have this. I'd appreciate any help.

If this seem to happen after the cap issue, did you wash the bike after your ride? May have a miss fire happening due to the cap not being securely fastened or water trapped creating a path to ground..... Or the carb.

If it seem to rear it's ugly head after the cap issue I would start there. :)

Thanks,

Cleaned the carb and the bike is back to normal.

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