Put my YS 45SE on a Ripmax Rapier for some fun. With a Modified Macs muffler and a APC 10X8 she pulled 12,500rpm. Not too bad for a motor that has about 400 or more flights on it.

try a 9x7 and bet you will go 16 or better

I have a ys 45se with a ma 9/7 triple, running 15% with a MVVS pipe turning 15400. The pipe has not been tuned to the prop yet though. Oh, and the motor has only had about 6 tanks ran thru it. I am looking forward to see what it will do after it is truly broken in.