I think all the cranks on these twins are balanced to 85%. Not sure on yours but my 68 T120R called for that %. There was a thread awhile back discussing the pros and cons between Dynamic and Static balancing that goes into detail about what to weigh and how to come up with the figures. Do a search in this forum. Some good information. I had mine dynamically balanced to 75% and it is really smoother. I let a friend that has several Triumphs ride it this morning and he said it is the smoothest Triumph he has ever ridden. I don't know if or how much smoother it might have been if I'd taken it to 85%.