I just ripped the engine apart on my '04 CRF450R and will be shipping my head out tomarrow to mxtime to get a valve job done. The shims were down to 1.30 and 1.40,so I wanted to get it good for the summer. I'm also thinking about throwing in a new piston/rings while I'm at it. So,now that the head is off what points of interest can I look for? The cylinder is is excellent condition with crosshatch. I guess its to be expected that at the top of the cylinder has the rougher surface ring around it. So do you think its still a good idea to put in a new piston? And if so does the cylinder need honed and stuff. And do I just order a stock sized piston,or do I have to take it to a bike shop and get them to check the specs on it,or can I do that myself with my micrometer? And are there any visual signs to tell me how bad my valves and/or seats are without taking them out? I'd like to know just how bad they were before I ship it off for a makeover ya know. I could probly get them apart,but I think mxtime would rather have them the way they are. Any other things I should check out while I got it all apart?