Hi Hal,
Everything you wanted to know about Whizzer clutches, but were afraid to ask....
The pulley on the flywheel is 2.5" [approx.], the drive pulley on the clutch [manual & automatic] is 5" [approx.] affording a 2 X 1 ratio. The output pulley on the manual is 3.5" [approx.] or 90 MM, and the automatic was offered as a 3.5" [90 MM] standard. Then a 50 MM [1.968"] was offered to owners who wanted a little more take off, more hill climbing ability, but had NO top end. Then the 70 MM [2.7559"] was introduced and was much closer to solve the take off problems and still have some top end. The rear sheeve is 15". If you do the math always count the rear sheeve as 15.75" becuase this correct the numbers to allow for the belts sinking into the pulleys. An example is 2.5" / 5" / 3.5" / 15" = 8.57 X 1, however the motor turns 9 times for every time the wheel turns once, therefore the actual numbers are 2.5" / 5" / 3.5" /15.75" = 9 X 1. If you want to carry this information to another level, try this... at 5000 RPMs on a 26" with the 90 MM clutch the bike will travel 42.969 MPH. At 6000 RPMs the bike would achieve 51.563 MPH. And at 7000 RPMs the speed would be 60.157 MPH. Or as we travel down the back roads of NC at 8000 RPMs the speedometer runs out of numbers, but the caculated speed would be 68.75 MPH [or the needle between the two z's in the word Whizzer at the bottom of the speedometer].
The hardened bearing race is installed on the output side of the clutch.
Have fun,
Quenton