WR 400 Carb Slide Problem?

I lost the top end of my 98 wr 400 last weekend. I pulled it apart to find out that the carburetor slide was breaking apart and pieces of it went into the piston and through the valves. Has anyone heard of such a thing before? Any suggestions on a cheap rebuild? Thanks for any replies.

Hey CJ22,

I have gone through two of those plates. (Is your throttle stop cut too short? I think that is what is causing my bike to go through those plates. They say that if the throttle stop is cut too short, it allows the slide to go to far up in the carb, and it starts causing vibrations that will crack the slide. Just a guess.)

But, on a positive note, I pulled the cylinder off the second time it happened, and the whole thing (cylinder walls, piston top and rings) looked great. No problems at all. I put it back together, with a new slide, and been riding ever since.

Do you have damage that you can see, or are you just thinking that you probably do?

Reason I say this is because that slide is some thin, brittle aluminum, and EVERYTHING in that combustion chamber is some tough stuff, and I really think the slide CAN NOT DO much damage in there (unless it holds a valve open, then there is a problem).

Good luck!

Thanks for the tip. I do not think there is much damage, but I know the engine has a lot of miles so while I have it apart I think I will put a new piston in it. I am concerned about the slide though. Do you know if anyone makes an aftermarket slide that is stronger. Or maybe Yamaha improved it in later years.

I think that they have redesigned the plate.

That, and somebody here on TT was making some at some point in time. Somebody from Singapore, if I remember correctly.


I think that they have redesigned the plate.

That, and somebody here on TT was making some at some point in time. Somebody from Singapore, if I remember correctly.



Your right. It was someone for Singapore. His user name was aremantroy or something like that. When I get home tonight I'll check and see what its is and post back here.

Ive kept his name on file... (you know, just in case) :D

Well, I thought I had his name on file but I dont. I know Im very close though on his name.

Brandon is right though. If your throttle stop has been removed or cut too short then your slide is hitting the top of your carb when you whack the throttle open and thats what is cracking the slide. Take off enough of the stop so that 9mm remains from the head of the bolt to the end. My stop stock was 17mm so I took off 8mm with a dremmel tool.

That will give you maximum performance and you will never have another cracked slide. :)

hi momilkman...... glad that you remember me...

I havent been posting on wr400 forum but did some posting on the yz forum.... but have always been actively reading the posts

i do have the carb slide made from aluminum (cnc)

let me know if you want it....


Hi aremean_troy,

Glad to see your still around. I dont hang around as much as I used to too, I just saw this guys post and your the only one I know of that has ever sold one of these slides made out of a better material than stock.

Id just PM CJ22 if I were you since he may not see this thread since I brought it back from the dead.

Take care. :)

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