I was wondering what the proper peak rpm is for these machines. Its a 1990 650 and I have changed the gearing to 20/39 and put a 1.25 track on it. Oh yes, its peak rpm is 75-7700, and I think there suppose to run at 8000?

650 Wildcat peak rpm is supposed to be 8250-8500 per the 1988 Wildcat 650 Service Manual.
I know a racer who SAYS he tuned his to 9000 for radar runs and ran over 100mph.

Definitely follow the OEM spec for peak RPM, or if you have aftermarket pipes, then follow the pipe makers spec. You will not get more power by overrevving, you will get less, unless your engine and exhaust has been rebuilt/tuned specifially for it.

8000 and not a rev over will be your most power, if anything go 7900 to 8000. After 8000 the power drops off dramatically if I recall and 7900 is only a little less then power then 8000. This is with stock pipes.

8000 and not a rev over will be your most power, if anything go 7900 to 8000. After 8000 the power drops off dramatically if I recall and 7900 is only a little less then power then 8000. This is with stock pipes.[/b]
Please post your source for your rpm/hp claims.
Arctic cat service manual says 8250-8500 for 1989 Arctic cat 650-no hp claims.

For the 700, which is virtually identical in configuration, PSI Performance says 8200 with stock pipes for 120 hp, 8100-8200rpm with PSI pipes at 128 hp, 8300-8400rpm, PSI Pipes and PSI porting for 135hp.

Snowtech magazine showed some rpm/hp charts for the newer 800cc AC powervalve/ casereed twin that gave the rpm range you stated. Are we talking the same engine?
Do you have some data that shows that AC and PSI performance don't know what they are doing?

Edit: that may have been a 900 AC Twin that snowtech dyno'd- can't locate the magazine right now.