Valve life Q's and Head rebuild?

I have a 05 wr450f and the girlfriend has a 06 wr250. I just shimmed her intake valves last night (exhaust needs it soon, they are at the low end, but I didn't have 5 170 shims...) and I want to know what I will be in for in the future...

How many times should the stock valves be shimmes before they are toast?

What all needs done when it is time to replace them? guides, seats, springs, retainers, or just drop in new valves?

Where is a good shop to get this done, if I need machine work?

What are the pros and cons of using something like the po-x SS valve and spring kit? We mostly ride low RPM singletrack, though I let her rip more than the girl...

differences in rebuild procedure between Ti and SS?

Lastly, where is the best place to buy OEM Ti valves? (I assume TT store, but the buggers are expensive! I know it doesn't cost Yamaha that much, 1/16th of the purchase price in valves alone? I think not..)



I say shim them, and keep an eye on them. If they stretch again after only a little run time, then I would replace them. Yamaha's last quite a while, but that all depends on the riders abusive right hand!!!

I say run the stock OEM ones instead of the Stainless. Stainless will last longer, but you will lose some power on the 250f. More than I'd be willing to trade away. On the 450, that's a different story, seeing as how you have plenty of power.

You should be able to get away with just dropping in new valves when it's time. The valve seats usually are fine.

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