HIGH idle

I have searched and searched, tried things, but no luck. My 99 WR400 was running fine, then after about 2 hours or riding I noticed the bike idling very high. I turned out the idle adjustment all the way and no help. Things I have messed with are: idle adjustment, throttle cable adjustment, air "screw" adjustment, hot start troubleshooting, air leakage around the carburetor clamp area. The only thing that seems to lower the idle permanently is to pull out the choke (thereby cutting off air, right?). All help appreciated.

I just got this bike last week, and do not have a repair manual or owner's manual. I have not checked the ohms on the TPS but I have read that a "bad" TPS would not cause high idling.

take off your carb and inspect the carb slide (or what the manual call as valve pin)

its a floating metal plate found on your carb slide. if you find a crac....its a must to replace it.

Thanks!! You were absolutely right. My part has a big chunk missing. I've run the bike at least 30 minutes since I noticed it idling high. Therefore, I'm assuming that whatever broke off, has left the motorcycle.

Any suggestions on a replacement (stock or aftermarket). Any thoughts on checking the motor, etc. for that broken piece?


if the broken bit went in the engine, and the engine still runs well (with good compression),you are a very lucky man :) If there is a piece missing, I'd pull the head off just to be sure. Only takes a few hours to do, then you'll know for sure :D


Broken Carb slide is thought/proved?? usually to be a symptom of too short throttle stop. Did you remove or file down - this is one of the 'free' mods. May reoccur if you dont fix that.

Just to clear up (maybe): The 'air screw' you refere to is probably the fuel screw, if you were adjusting the little bitty screw in the recess on the underneath of the carb. If I'm worng, scuse me.

The "airscrew" os only such if you changed the Pilot Air Jet to an adjustable 'screw' one, which means messing with the innards of your carb.

I bought this bike used and rode it a few times before this incident and before I needed to find info here at thumpertalk. After reading some of the free mods articles I looked at my bike. The throttle stop isn't even there. So I will replace it with a shorter than stock one soon.

But that leads me to a question. I would think that by letting the throttle slam shut (releasing the throttle grip) would be what causes the carb slide to weaken (continuously smacking the bottom of the carb), if so how would that have anything to do with not having a throttle stop? I can't see how increasing the throttle (twisting the grip open) causes the carb slide to weaken?

Oh, you were also right about the small screw on the bottom of the carb I was turning. I've yet to learn the correct terminology for all this "stuff".


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