Time limit for titanium valve stretch?

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12/31/2017 12:27 PM

As I’m rebuilding my 08 CRF450, I’m wondering if there should be a time limit or overall length service limit dimension to compensate for creep length increase over time on the titanium intake valves? Wear on seat face is negligible, slight pitting less than .001” depth, 57 hours on the valves, but concerned the stretch (if any) may lead to plastic deformation and failure? A service limit dimension would require a gage point on the angular seat surface to the collar feature? Idk, probably over thinking it and should just recut the seats with new valves, but everything looks good and mating surfaces are worn in and sealing looks good. Would like to assemble tonight and finish the job, but also want peace of mind that it’ll hold together for another 60 hours....

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12/31/2017 4:58 PM

If you have had to do a shim job or 2 previously , then I would suggest do a valve replacement and cutting the seats.

Paw Paw

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12/31/2017 6:48 PM

Paw Paw 271 wrote:

If you have had to do a shim job or 2 previously , then I would suggest do a valve replacement and cutting the seats.

Paw Paw

No, have not shimmed yet. I think i'll just replace them, don't like the pitting on the seat surface, although it is minor.

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1/1/2018 4:50 AM

At 57 hours on the valves and no adjustments with them still in spec i would run them until they started to move. Unless of course you are a person that runs the bike on the rev limiter , in that case id replace them while it is apart.

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1/1/2018 7:16 AM

i have 140 hrs on my 08 crf 450 stock valves, never adjusted did a piston and cam chain at 100 looked at the valves and ran them, mostly to see how far it would go , which is much longer than i thought

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