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Old 12-30-2012, 08:29 PM   #85
Loose Pre Unit
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Joined: Dec 2001
Location: New Zealand
Oddometer: 4,549
I just calculated it all out, and then lost it all....should've written it down the hard way. Anyway, my final point was that bore/stroke is about piston speed, and you can't compare a 650 to a 1,000cc engine....better to compare the R65 to a Triumph 650. At 7,250 the 82mm stroke Triumph has a piston speed of 19.8 m/s, or 3900 ft/min. The 61.5mm R65 is doing 14.86 m/s or 2925 ft/min, at 8,000 the R65 is 16.4 m/s or 3228 ft/min, at 9,000 18.45 m/s or 3631 ft/min.

At 9,000rpm the piston speed of the R65 is lower than the Triumph at 7,000rpm - and the Triumph was considered to be a revver in it's day.
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