MY '00 400EX WILL IDLE FINE, BUT WHEN I GIVE IT THE GAS, IT DOES'NT PICK UP ANY RPM'S. I ALSO NOTICED WHILE LIMPING IT BACK HOME THAT WHEN THE FRONT TIRES ARE OFF THE GROUND THE MOTOR QUITS AND STARTS BACK WHEN THE TIRES COME BACK DOWN. I WAS IN SOME WATER THAT DAY, BUT NONE IN THE AIRBOX. REPLACED SPARK PLUG, CHECKED ALL WIRING
AND EVEN CLEANED THE CARB. THE NEEDLE IS INSTALLED CORRECT CORRECT ALSO. STILL THE SAME PROBLEM EXISTS! ANY INPUT WOULD BE A HUGE HELP! THANKS!

Hmmmmmm, that's weird?! What kind of gas are you putting in her? That might be doing somehting?! Sorry if i'm not much help

I think this problem has come up before in other posts so you might research it, but as I remember, the solution had something to do with a clogged vent tube on the carb. It sounds like your flooded. Also check to see if the float is sticking.

Thanks for the replies, guys. I am running 93 octane gas. I cleaned the carb well, put it back together and had the same problem.

gary if you've been running in sand your carb might have some in it....i know you cleaned it but sand could be stuck in the throttle cables(if your 400 has a throttle cable) my friends did the same thing last night and we cleaned the cables and carb with some WD-40, my friends throttle got stuck a bit and was hard to push

The check valve in the overflow needle fails quite often (always). Usually you can drain the carb several times and it will correct itself. I foyu have alrteady cleaned the carb (disassembled) I would suggest cleaning it again using yamaha carb cleaner. If you are going to ride in water over the bowl of the carb, plug off the drain line at the bottom of the carb, but just when you are riding, the overflow needle is there for a reason.

gregsims@excite.com

check the fuel hose for anything that might have got caught in there

My 400ex had the exact same problem you described and I found that my jets were clogged. After having the carb on and off twice cleaning them I put an in-line fuel filter on it and haven't had any problem with it since.

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Jhall,

I bought a simply built clear plastic Fram filter. I haven't installed it yet. It is not that big, but not that small either. What did you use? I guess it doesn't hinder fuel flow, huh? Was it difficult to install? Etc? Fill in anything I may need to know. Thanks.



Garyc400ex,

You may want to check your ignition coil located under the gas tank behind the right fender. I know people in the past have had problems with their 400's running smoothly when the coil is dirty/wet. Check it out, be sure it is clean; this could be your problem. I think "Tree Farmer" posted a post that references this problem. He took his bike to the dealer and that was the problem. I think he covered his with something to avoid a repeat of the problem.