When To Replace Valves ?

3 replies to this topic

Posted August 06, 2005 - 09:18 PM


I'm looking at an 03 450 yzf and it appears as if it was well taken care of.He replaced rings and said the valves looked good. He is or was a more of a trail and play rider and did regular oil changes . It would be nice to know what to look for and some tell tale signs. Thx .

  • Anssi

Posted August 06, 2005 - 11:11 PM


The tell tale sign is that the valves go out of spec. The coating on them is extremely hard-wearing, and when the clearance starts to go down, it probably means the coating is gone and so will the valves pretty soon. However, the valves can fatigue and just break with little warning when they have enough hours on them. I replaced mine at about 135 hours, still in spec, but I wouldn´t have had the guts to go any further on titanium valves.

I would replace the valves on any F I bought if the seller didn´t give me proof they have been replaced a reasonable time ago or the bike had not been ridden for long.

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  • grayracer513

Posted August 07, 2005 - 09:08 AM


My '03 still has never required its first ever valve adjustment. What I recommend is that once the shim size is .20mm smaller than the original shim, the valve has completely worn through the hard coating, and should be replaced.

Our 250F went to around 400 hours before it got to that point. It is my opinion that almost all valve failures in YZF's can be traced to weak or broken valve springs, and are not the fault of the valve itself. They simply weren't made to be bounced off the piston. :D

  • Fastkid591

Posted August 07, 2005 - 02:55 PM


I do mine about every 8 months. (full engine rebuild)

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