WR400 won't idle w/o choke

Hi Everyone,

I have a 2000 WR400 that I bought used about a yr ago. I rode it all last winter and stored it through the summer.

Now when I start it it'll start fine with the choke on but dies as soon as I turn the choke off. It'll run if I hold the gas on while I turn the choke off but dies as soon as I let off the choke. I tried turning the idle up but I have to turn it up so much to get it to idle that then I can't start it b/c the gas is always on.

I've tried adjusting the pilot screw... starting at 1 1/2 turns out and going in 1/2 turn increments out to 3 turns out. Didn't change anything. Also pulled the carb opened it up pulled the jets and sprayed it all out with carb cleaner... also didn't help.

Any ideas?



I had the same problem on my 98 YZ 400. i took it to a shop and they told me the motor needed to be rebuilt and that the bike was abused. The motor had just been gone through. I took it to Yamaha and there was on o-ring in the carb that had gone bad. It cost me over $300 but it runs like a champ now. It may be the same issue. I hope this helps.

drain your gas from the tank. Then clean all your jets, I am betting your pilot jet is plugged, I had exact same prob after lettin it sit for awhile then used some crappy gas I had sitting around.

I should clarify, I cleaned my jets but didnt change the gas, so I ended up cleaning the pilot 2x, because I didnt change the gas.

Youd be suprised at whats sitting in the tank

rotten gas in the carb. i have seen it 100 0000 times. in the spring that is what pays my paychecks :banghead:. when gas evaporates it leaves nasty slime in all the small jets and holes of the carb.

i would suggest taking the carb off and bringing it to a good local shop for a "full carb clean". if it is a good shop/tech, they will:

-completely dissemble it

-soak the carb body in a hot tank

-blast out the body with brake clean then air

-soak all the removed parts in "carb clean"

-clean all parts with brake clean and then air

-re assemble

-bench test

the process takes a few hours but just because of soaking time. it only takes about 20 min in hands time. shop should charge any where from .5h to 1h @ there shop rate.

also if it has been sitting for a while change the oil and drain the gass tank!

I agree w/ the bad gas. My 98 WR400 had the exact same problem. It sat for awhile, and I took it out to play without putting new gas in it. :banghead: All the crap at the bottom of the tank sucked through the carb and jammed it up. One good thorough cleaning did the trick! :banghead:

I agree with the other posts about bad gas and clogged jets. I just had this problem. Take the carb out and clean it thoroughly. Take the jets out and make sure they are not clogged. Chances are they will be, that's what I found with mine.

Thanks everyone. I pulled the carb and the pilot jet was completely blocked. I blew it out along with all the jets, put some fresh gas in and it's running perfect now.

Looks like I'll make it to Superstition this coming weekend after all!

Thanks again,


that happened to me just today. me and my dad went to take it out so i can get used to it and it wudnt idle so after hrs of trying to fix it we took it in and in 2hrs the had it back ti us it cost 110$ and we took it out and it started on 1st kick and didnt giva anymore truble

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