Hey Rick if you’ll do the 9750 rpm I’ll watch.
Greg speed really isn't my goal with the 66cc China girls so I run 48 t and 44t normally for daily, no pedal riding, but I do have two motors that will crack that 10,000 rpm mark with ease. One is a modified reed motor and the other a piston port which has been highly modified. The piston port has a twin brother which decided to part with it's rings a few years back at 12,000 plus. When it came up on pipe it felt like I'd shifted gears (using a tuned KTM expansion pipe) but while doing back to back to back runs of a half mile each at the airport it decided enough was too much. I felt really destructive that particular day. They do blow or don't last long when you push them past 8,000 rpm very long or very often. I test with a 48t sprocket to keep the speed down, rpm was my interest, but I was still zipping along pretty good that crisp fall morning.
I'm thinking of changing my 48t out for a 36t sprocket on my hybrid for a less busy motor between 30 mph and forty...at least I have a sprocket on order for it. I'm hoping it won't be too herky- jerky at 10 to 15 mph, but I'm not holding my breath. The piston port engine was never a daily rider & became almost un rideable at legal town speeds (under 25mph) even with a 48t sprocket, just too high strung. Since I use the electric hub for all my takeoffs I still won't have to pedal with the 36t sprocket, unless I want to, from dead starts such as at stop signs etc. The reed valve engine on the hybrid isn't anywhere near as high a tune as the piston port I described, but still the 36t may not work well enough for in town daily duty.
I'm aware anyone (me) can claim anything, when it comes to performance; so for those that doubt just have a good laugh at my expense and consider the tall tales of the Old guy as entertainment alone!
Still just having fun, Rick C.