I went riding today and about half-way through my ride my engine started racing at with the throttle in a closed position. About 3-4,000 RPMs. When I got home I removed the Carb and much to my surprise there was a big chunk of metal missing from the thin aluminum plate that is located along side of the slide.

Evidently the missing piece went through the engine. Hopefully w/o reaking too much havoc along the way.

Is this aluminum plate available at the dealers and is this a common problem? my only thought on what would have caused the piece to break off is possibly a back-fire in the past.

Any thoughts on my little dilema would be greatly appreciated.


'98 WR400

this was a reasonably common failure on the 98 model. you can buy the alloy plate from a carb specialist. i believe they are better made now & there shouldn't be a problem again.

most riders have been lucky reporting no valve train problems etc.

so good luck


Hi Taffy, where can I get that alloy slide??



'98 WR400F, YZ timed, main:180, pilot:48, DVR needle 4th clip from top,

snorkel removed, YZ tank/seat combo, YZ front no.plate/rear fender,

DSP Ti exhaust system, Brembo front brake,steel braided hose, EZ clutch adjust perch,

Stroker billet rear brake reservoir

Did you check the intake runner of the cylinder head to make sure that missing piece isn't lodged inside? I can't imagine a piece of metal of that size passing between the intake valve and seats. If you remove the carb, you should be able to shine a flashlight and inspect the area around each intake runner. If that piece is caught in there, it's possible that it could eventually shift and get wedged between the valve and seat and prevent that valve from closing. Not a good thing!

Sudco ph#1-800-998-3529.

cutn' paste from somewhere else.

don't ask a brit we dunno nuffin.


By the way Taffy, I finally mailed that cracked slide to you. Sorry for the long delay!


99WR,WR timing,throttle stop removed,Uni filter,E-Series pipe,carbon air box,Pro Tapers,lights removed,YZ tank,13 tooth sprocket


if i told everyone iwas delaying YET AGAIN they would say i was a wuss!

glad you explained the delay.

thanks again


Nope, not your fault... mine.

My slide broke at 5000km and again 1000km (600mile)later. No help from Yamaha as to a fix. Just had to replace it and will now check very often. Not much fun on a ride if in the back of your mind your thinking "is it due to break again"

Hey I am about to mill out a stainless steel version of the slide. I will keep you guys posted on the result. Will start out this projet soon hopefully before end of Dec. :D I am facing the same problem and have break 3 times no kidding :)

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