04 yz450f valves help

4 replies to this topic
  • Wildcard221

Posted April 17, 2012 - 02:19 PM


I just found out that if you have to reshim your bike more than .10 different than what you had in it you need to redo the valves.....
so how do i go about doing that..do i have to rebuild the whole top end or can i just do the valves..? Because all 5 of my valves are at least .10 different from what was in it, but after i changed the shims and re jetted it for my altitude it fires right up on the 3rd or 4th kick so do i really need to do all that work?

Edited by Wildcard221, April 17, 2012 - 02:22 PM.

  • jjhubbard15

Posted April 17, 2012 - 03:46 PM


depends on if your valves stretched or it the valve seat has worn in that far, you also need to know how much play the valve guides have in open position to know if you need to have them done. Sounds like you may need all of the above if you have adjusted that far

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  • grayracer513

Posted April 17, 2012 - 06:42 PM


If you doubt that it needs a valve job, run it for 5 more hours and check the clearance. You will most likely find that the clearance has already closed up even farther. This is because titanium valves depend on an extremely hard, but extremely thin coating of a titanium nitride compound. Valve clearances will stay the same for years until the coating wears through, and at that point, the underlying metal is too soft and wears very rapidly. What's the worst that can happen if you let it go? You'll drop a valve head at 9000 RPM and completely destroy the engine.

To repair the problem, remove the head and take it to a competent small engine machinist accustomed to doing precision valve jobs on motorcycles with titanium valves.

  • Wildcard221

Posted March 05, 2013 - 06:08 PM


well i know it has been a loooong time since i responded to this, but is it possible to have it recoated with that titainum stuff that your talking about grayracer or do they do something different when a machinist does his job

  • grayracer513

Posted March 06, 2013 - 07:34 AM


Titanium nitride coating is not something that can be done by a small shop, and if it could, doing a small job like a handful of valves would be very pricey.

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