Hobot, I don't think it was a matter of 'getting by' with a lower balance factor when using isolastics. I believe the intent was always to reduce vibration. A factor of 58% was used so that the bike did not shake at low revs. The isolastics were also used to dampen vibration, and isolate the rider from the motor. The effect was to make the motor unsatisfactory at high revs, the centrifugal loads cause the cases to fail by cracking through the drive side bearing housing. The isolastics produce a handling problem and require adjustment if the bike is to handle well. The whole thing was a different approach to the Manxman 650, but it had to be because of the increase in capacity. A rigidly mounted commando motor with a high balance factor, in a non-isolastic frame is unsuited to riding in traffic on public roads. But I believe it is the only way a road racer should be constructed, however the vibration at low revs must be allowed for. I seriously believe that if you want a road commando to go fast, you need two bikes - one for slow riding in traffic, the other for blasting around twisty back roads . With my racer I use a factor of 72%, and the motor rigidly mounted but with allowance for some spring, so the forces don't stress the frame and crack it. It vibrates like hell at low revs, but going up through the gears,and flat out, it is difficult not to over-rev it, it is so smooth. It is a really nice bike to ride in a race, I love it. It causes no anxiety, and inspires confidence . Dennis Poore might have been better off producing a sports version of the commando alongside his normal product. I believe the 750cc short stroke production racer used isolastics and was a bit of a fail. I suggest the compromise required to reduce vibration at low revs was a bad move.
