You should have .006" clearance on your intake valves and .011" on the exhaust, with .014" on the decomp lever.
If you have 0" clearance you will have to use the smallest shim and measure from there.
If the head has a lot of time on it, it would be a good idea to remove it and inspect the valves and seats. Replacing the stock valves with the Kibblewhite stainless steel valves is a good idea and they will last a long time if you keep your valves adjusted. Be sure to use the Kibblewhite spring kit.
The '02 engine should have the exhaust valve rocker arm replaced and the cam chain adjuster upgraded if it has never been done. Check the ex rocker roller for wear or scoring. A new cam chain is a good idea on an older engine. Also, check your cam for wear. If the valves have been running tight for very long there may be wear on the cam.
Probably not the answers you wanted to hear but, there ya go. :cool: