Busted Valve Float #2!!!


3 replies to this topic
  • bdmmotard

Posted April 13, 2005 - 02:04 PM

#1

i know this is a common problem, but this is getting ridiculous. my 2nd valve float just busted on my 98 wr400 in 4 months!. I'm trying to get keihin to replace it (not holding breath). any suggestions for a stronger part? i remember hearing something about them updating it. I'm seriously thinking about going with a different carb. to get back on the road i guess i'll just order another along with the seal. best options for oem parts? AAAAAARRRRRGGGHHH!

  • Frostbite

Posted April 14, 2005 - 05:02 AM

#2

Are you talking about the Throttle slide plate? I heard of a few guys that broke 2 in a row. It may be that the rubber O ring was installed backwards. Backwards it may not provide a cushion to the plate causing it to crack sooner. I broke mine, replaced it and it has been fine for 2 years.

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  • bdmmotard

Posted April 14, 2005 - 08:25 AM

#3

hey how'd you get a pick of my plate! :naughty: for some reason yamaha parts catalog calls it a valve float and even a "valve needle" depending on the year, don't ask me why.

i installed it right, but it was the old seal. so this time i ordered both. glad to hear yours lasted 2 years. this is my daily rider so it takes a beating. but 2000miles of hard street riding/racing and the valves were in spec!

  • Frostbite

Posted April 14, 2005 - 09:18 AM

#4

The wear pattern on mine seems to indicate that the damage is being done when the throttle is closed. Pulses from the engine rattle the slide and plate back and forth in the carb body and at small throttle openings, the bottom of the slide plate is trapped in a slot. My humble theory is that the bottom of the plate is held snugly in the slot while the rest of the plate and slide is free to vibrate back and forth.This kind of wiggles the bottom corners of the plate and they crack off. With the O ring in properly there is a bit of cushion, backwards you have metal on metal. At 1/2 throttle everything is free to move together. Did the bottom corner/s brake off your plate like mine? Looking at your slide plate does the wear pattern seem to match the carb bore when the throttle is closed?




 
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