Ok here is where Tom the anorak chimes in....................Look up RC148 or RC149 Honda, it's there 5 cylinder 125cc four stroke GP bike from circa 1966 these revved to 22K. I've alway found bike engines to be more innovative (a prejudiced view of course) Also form the 70's there was honda NR500 oval pistons 8 valves per revving to 25K. Granted F1 engines have heavy valve trains than little tiny dime size valves in 45 year Honda GP bikes do. (check out 5 cylinder honda on You Tube.......wicked engine note)

One other note Dave sort of brought up, gearing. Keep in mind that bikes usually have a final drive that equates to 2.6 to 1 and are running on 17-18 rear wheels. I don't know what top gear is in a Hayabusa but in a Datsun with 13 inch wheels the gear ratio is likely much lower than the bike by maybe as much as 50%. So 6000 RPM's in first could be as low as 15 mph etc. In our Yamaha powered Sports Racer running on 13 inch slicks 12K in 6th was something like 142 MPH...............a solid 40 mph less than the bike.

Tom