Very interesting.. The progression of primary drive ratios from 500/550/650 have always been to a lower numerical ratio. The crank gear is bigger, the clutch gear smaller.
500 - 3.246
550 - 3.063
650 - 2.740
This spins the clutch and trans faster, then the adjustment is made in the final drive. Since HP is torque x rpm, a faster spinning clutch and gearbox sees less torque, and torque is what bothers clutches. On the downside, there's more frictional losses in a faster spinning gearbox.
The clutch hub shown goes the wrong way with a higher (numerical) primary reduction which will send more torque through the clutch, presumably this is why it needs an extra plate? I suspect the different hub was neccessary to accomodate whatever main shaft was used for the CR box? We can only conclude that these must be borrowed parts instead of purpose built because they would never choose a higher ratio primary drive.
Unless,... they were going for less friction losses in the gearbox and weren't so worried about clutch slippage? Actually I like this thinking for a race bike. Why not use an old cb550 primary ratio and add thinner plates from a modern sportbike? Two opposing strategies, one goes for durability, the other for more efficiency.
Does anyone know the primary drive ratios, diameter and plate counts for a modern 600cc sportbike? It would be interesting to see which way evolution took us?
