Stumped, PLEASE HELP.....

Background: 1999 YZ 400F Ran bike last Sat. (ran great) for 3hrs. Started raining, bike sat until it stopped. When it stopped raining I got the bright Idea to go play in the mud. 5 mins into the ride, the bike starts studdering and lerching and having some serious bogging issues. Got so bad that the bike wouldn't even take off from a stand still (would start though very easily). Got it back to camp and It sat for the remainder of the weekend.

What I have eliminated I think: Drained about half a gallon of fuel out of the tank thinking water somehow got into the tank. ran it up and down my road for a couple laps and a serious bog issue is still very apparent. I'm thinking water in fuel not the issue?

Problems I am considering: Clogged jet/ needle? Bad throttle pos. sensor (if it has one, no Idea)? CDI unit?

Please help with any other problems you all might think may help me solve this grand mystery. I feel the bike had plenty of time to dry out before the run through my neighborhood 2 days ago. Could it be just an electrical connection some where?

Help Please!!!!

Just because water isn't in the tank doesn't mean it's not in the carb. Drain the float bowl, and put 4 oz of ethyl (preferably) or isopropyl alcohol in your tank to absorb any left overs.

I never thought of that. I'll be doin that this weekend. Thanks for the tip!

Also check the neck from the airbox to the carb and get some compressed air through there.


check your plug wire and make sure your pet cock isnt being restricted by some foreign debri.

All great suggestions. Thank you all.

Finally got to tearing into my bike tonight and what did I find........ My plug wire somehow became dislodged from it's intended position. I guess I was freaking over nothing. Thank you for all the great ideas.

Glad it worked out well and painlessly.. :thumbsup:

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