i'm having some problems with my 99 400ex. the other day i was crossing a creek andmy bike stalled. when it finally started it would pop on full throttle riding and wouldn't accelerate correctly. later on that day it wouldn't even rev past half throttle. it would just die like it wasn't even getting gas. i figured water in the carburetor. nope. my plug cap was coming off so i put it on all the way. nope still doesn't run correctly. i drained my float bowl. nope still won't rev right. my exhaust is loose (white brothers). the rivits are coming out. could it be that. not enough back pressure. my air box was dry as can be so i don't know. could my main jet be plugged.or something holding my needle from going up all the way. any help is greatly appreciated.

 

hey fast400
how deep were you?did you take in water through your exhaust?or even through the air box?you might have water in the combustion chamber.take out your spark plug completly even out of the plug cap so you dont spark turn on/off switch to off,crank it over several times,put back together warm it up and change the oil.not sure if this helps but if you took on water in your motor your motor will appreciate down the road.
see ya papaw.

 

i had this problem with my 300trx and it was water in the gas. if not how i always fixed mine after flodding it was i would find out where it would die (u mentioned it wouldnt go over half way) and hold the throttle a little before that and let it run like that for a while. keep doin this until u get all the throttle back. im not sure if this will work but its worth trying.

 

My EX had the same problem when I crossed a deep water crossing. The water was up to my exhaust pipe and it died right in the middle of the crossing. It wouldn't start until I put the choke on all the way. With the choke on I was able to move the EX out of the water, but as soon as i took the choke off, it died again. All i did was pull the plug and used some sandpaper to clean off the electrode. Worked just fine after that. Give it a try, it wouldn't hurt.

 

I had a similar problem with my ex .. take the carb and look in to see if the "plunder" type thing is moving which means your not getting enough air, it came unhooked on mine and i wasnt getting enough air and the motor wouldnt rev past half.