This weekend I'm going to be putting my 2006 YZ250F top end back together, and have a few questions. 1) I bought a piston kit for an '08 YZ250F. It has an arrow on top of the piston. Can someone verify for me which direction the arrow should point? 2) Valve shims - I'm curious, do valve shims just sit "loose" inside of the buckets? When I pull a shim from a bucket, and then reinstall it, do I just set the shim back in the center of the bucket? 3) Cleaning parts - I was told to use a scotchbright pad and bathroom cleaner to clean all of the parts before assembly. Just doing the top end (not doing valves), which parts should a clean and what should I not clean? Is bathroom cleaner ok? 4) Grease - the manual talks about putting some kind of grease on certain bolts? It looks like the head bolts, etc. What type of grease is this? Is it necessary? Thanks!