WyldCFH
Drop a Gear and Disappear!
The shims will not spit out because of rpm unless there is a problem with valve springs etc. If any of you are old enough to have owned an early Z900 Kawasaki, they could be turned well beyond 9000 with no problem, TT350 Yammy 10K, FJ110 Yammy 11K. The reason for putting the shims under the bucket on a rocket is to save weight on the reciprocating valve parts and to enable a lager lift cam to be used. The cam is running on a 28mm bucket instead of a 25mm shim. If you want a rpm limit at 13000 it can be done, even with a PCV and ign module you could up it to 11k. There is no "secret". STOCK springs are beyond there design brief above 7000rpm especially for any length of time.
So it's not the shim placement, it's the springs working capability. Good info to know.