I've seen people do 50-55 without a clutch kit in high (really don't recommend doing), just think if your bike tops out at say 75 like these 850s (average top speed) and tracks top out at 50 your always pushing your bike around 20+ mph (engine wear wise) every where you go to get the same speed as tires.
Scrambler at the dealer put stm primary and secondary and they had it up to 65 in the parking lot, and it had way better throttle response from getting the lower gear ratio (belt sitting lower in primary and higher in secondary) and the higher ratio and it did not seem to put near the strain on the motor.[/QU
When you say you have seen them run this fast, are they and you going off what the speedo says or a GPS? The reason I ask is I have them on mine now and the speedo is way off says I'm doing 50 when I'm going 25-30mph. So what it shows on their speedo is not how fast they are really going. So 65 out of the scammy just can't be true.
remember the stm is MASSIVE amount of power gain compared to stock, its not just a clutch kit, it complete new billet clutches, lower gear ratio plus higher gear ratio, also for got to say exhaust and fuel tuner, but speeds where next to my 850 with 27in itp mulights