Symptoms of a fouled plug?

Yesterday at the track, my bike ran like crap. It would start and idle just fine, and slowly rolling on the throttle was fine, but it would bog down & pop when I'd lay into it or try to roll on at high speed through the gears. Before tearing into the carb, I wanted to start with the least-intensive course of action: I pulled the plug and noted it was black. This is a new plug with ~4 hours on it.

SO, I recall my Thanksgiving adventure where 2 guys got their bikes mired in mud (to the point where we left the bikes there until the mud froze a couple days later) and I was the only guy (barely) able to ride mine out. I recall that my vent tubes underneath got so covered with clay-like mud that they weren't breathing, and my bike started running poorly (backfiring, hesitating, etc). I got the bike all cleaned up & made sure the hoses were clear, and started it up to make sure it sounded good, which it did...until I went to the track and realized it was running poorly.

My assumption is that the plug got fouled because the carb couldn't breathe and it burped extra fuel into the cylinder, eventually fouling the plug. The bike was running great up until this misadventure. I put in a new plug today, and am hopeful that this will fix the problem. Is that an overly optimistic assumption, or could something else be wrong? I also went ahead & made sure to route the top vent hoses into my airbox, based on other posts I've seen about mud & water.

Thanks for any insight. I just don't want to have to pull the carb and deal with that...

I find a fouled plug, its always hard to start. It will buck, shot ducks etc. Also, just starting it in the garage to show all your buddies your new Yoshimira will also foul it, as you just blip it a few times to impress them and shut it down. Anyway, I had enough fouled plugs over time and I just bought one of those plug sandblasters. Toss in a new one and see how it runs. I know if the vents are plugged, it will run rich and this could easily foul the plugs.

yep, that's my thought as well - it ran too rich and fouled the plug. Wish I would have confirmed this before I tried riding yesterday...that was a bummer.

So I could sandblast that plug and use it again, huh? Where do I find one of those plug sandblasters?

Yesterday at the track, my bike ran like crap. It would start and idle just fine, and slowly rolling on the throttle was fine, but it would bog down & pop when I'd lay into it or try to roll on at high speed through the gears. Before tearing into the carb, I wanted to start with the least-intensive course of action: I pulled the plug and noted it was black. This is a new plug with ~4 hours on it.

SO, I recall my Thanksgiving adventure where 2 guys got their bikes mired in mud (to the point where we left the bikes there until the mud froze a couple days later) and I was the only guy (barely) able to ride mine out. I recall that my vent tubes underneath got so covered with clay-like mud that they weren't breathing, and my bike started running poorly (backfiring, hesitating, etc). I got the bike all cleaned up & made sure the hoses were clear, and started it up to make sure it sounded good, which it did...until I went to the track and realized it was running poorly.

My assumption is that the plug got fouled because the carb couldn't breathe and it burped extra fuel into the cylinder, eventually fouling the plug. The bike was running great up until this misadventure. I put in a new plug today, and am hopeful that this will fix the problem. Is that an overly optimistic assumption, or could something else be wrong? I also went ahead & made sure to route the top vent hoses into my airbox, based on other posts I've seen about mud & water.

Thanks for any insight. I just don't want to have to pull the carb and deal with that...

Maybe if you didn't ride w/ such losers you wouldn't have these kind of problems.

I'd look inward Shuffler...what is the real problem here? Ask yourself.

A friend with an 01 yz426 had the same symptoms. Turned out he had dirt in his carb. Took it off and cleaned it, good as new.

I find that if I just start up the bike and not ride it that the next time will give me troubles. If you start it.....ride it.

I'm learning about that "if you start it ride it" the hard way...

I've had about 3 times now that after I started it I had to shut it back off and then play the "kick it until your leg is going to fall off" routine.

It's guaranteed to foul a plug if you do that.

And my experience with fouled plugs is that the bike won't start at all with one. I took mine out once and wire-brushed it and it worked fine afterwards.

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