WR400 carb slide breakage problem??

Hi guys juz got my 98 wr400.Hear alot abt the slide in the carb breaking.Discuss wif my mech. abt tis he suggest tat the slide broke because of the engine compression is too high n the stock exhaust is too restrictive hence the exhaust output bounce back n added pressure back to the slide to cost it to break.Not sure how true but I m now using a high flow exhaust wif min. restriction too play safe.

The thing that breaks is called the valve pin.

Most of the guys here get a replacement Valve pin machined out (last longer). The main reason for the short life span of the valve pin is due to a design fault as well as the high compression of the wr400. Another reason is that, the o-ring at the back of the valve pin is not replaced when it is worn down.

hope this helps


Check this out . I put this on my website years ago.

Hope it helps you.

Thankz for the info guys.But the machined valve pin seems to even cost a heavier damage cos there are alot of pple who changed it n had problems to their carb n had to change a new carb.Anyway the breakage is not due to the restriction of the stock exhaust? :)

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