Valves gone at 3700 miles?

6 replies to this topic
  • Mike_Hudson

Posted November 27, 2009 - 03:23 PM


Bought my 03 WR450 new. I just checked my valves again and the intakes are less than 0.0015 in (my thinnest guage). I have had to reshim the valves at ~1000, 2000, 2800 (intakes no clearance), and now at 3700 intakes slammed again. Considering the original shims were ~185s and now they are down to ~145, I have the motor apart now and will send the head out for new valves, etc. what to do now is obvious - rebuild the head.

My question is why did this happen. I know most folks are getting two or three times this mileage without valve issues. I run a twin air filter, normally use PJ1 or Bel Ray spray filter oil. I clean the filter every couple of rides. Air box always looks clean. In the area I live (alabama) almost all the gas has ethanol, so that is what usually goes in the tank (93 octane).

Mods to the bike are chopped up air box, JD Jetting (summer - 45 PJ/162 MJ; winter - 48 PJ, 168 MJ), FMF 4.1, Rekluse clutch. Bike doesn't pop on decel, so I don't think I am running lean.

Also looking for recommendations on a shop to rebuild the head and hone the cylinder.


  • grayracer513

Posted November 28, 2009 - 08:34 AM


I'm afraid there's no way to know why this came about so early, unless you spend a great deal of time in the lower gears, which would have run the engine some farther than the odometer would indicate.

As for a shop, ask around to see who does the head work for the local dealers, or try Engine Dynamics, or Millennium Technologies

  • Mike_Hudson

Posted November 28, 2009 - 06:14 PM


I would say I spend 90% of the time in 2nd and 3rd gear, so that may play some part. anyway, I'll be giving Eric a call to get the build rolling.

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  • TooFast

Posted December 01, 2009 - 01:52 PM


Have you been on the rev limiter a lot?


Posted December 01, 2009 - 02:56 PM


Have you been on the rev limiter a lot?

I beat the piss out of my 450's and got > 15,000 miles out of a set of valves. Somethings up to cause a a failure this early. My guess air filter or lean jetting but I think it would have to be very lean and by your numbers that doesn't look likely. Are you getting the bike real hot or boiling over regularly by chance?

  • Chas_M

Posted December 01, 2009 - 05:12 PM


Some folks attribute unfiltered carb vent tubes and crankcase breathers to at least partial reasons for premature valve recession.

  • RSAthump

Posted December 02, 2009 - 12:38 PM


how often did you change the oil?


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