First of all, if you are talking about the exhaust power valves, you should disassemble and thoroughly clean them when doing a top end. As far as other things to look for, everything is pretty standard and similar to other bikes. The one thing that is VERY important (trust me from experience), is that when re-assembling the cylinder onto the engine, be absolutely sure that the linkage fork for the powervalve (on botton of cylinder) engages properly with the pin coming up out of the crankcase. If this is not done, your bike's performance will be terrible, trust me. I learned this the hard way, once.