I know this subject has been pretty well covered throughout the forums but there are a couple of potential make or break details that I cannot find a definitive answer for. Mainly on the subject of valve seat preparation and lapping. For a little bit of background, I have an '07 CRF450r with approximately 40 hours on it (Vet B weekend rider). The intake valve on the left has gotten tight on me twice so I figure it's probably on borrowed time right now. The last time the shim was a pretty big jump smaller to get it in spec. Not going to touch the exhaust valves or piston since everything else looks really good. I'm planning on going a little off the beaten path here and throwing in new OEM titanium valves and just touching up the seats. If I can get another 40 hours out of $100 set of valves I'll be happy to do it again whenever the need should arise. A friend of mine who works on performance car engines (he has a race car) says no problem to "touch" the seats for me to clean them up and get it ready for new valves. The tool he's using is a hand-held device that centers itself in the valve guide and applies an abrasive device to the seat surface to grind it smooth. Does this sound right? Normally then you would lap the new valves in after regrinding the seats. If you can't lap the titanium valves, what would need to be done in it's place or do you simply not do anything? Would it makes sense to buy a sacrificial valve (cheap steel one) to use only for lapping the seats or is that not necessary?