- Joined
- Nov 26, 2009
- Messages
- 3,171
When Norton went to their longer 89mm stroke they used a 5.875 length rod and ended up with a 1:68 rod length to stroke ratio. This was tolerable in the Norton 650SS but with the heavier 750 Atlas pistons it was a bone shaker and isolastics were necessary for the Commando. The Triumph 750 had a better 1:86 rod stroke ratio and they didn't have to use Isolastics. A 6.4" length Norton rod gives a 1:83 ratio to mellow out the vibes and stress.