A65 Thunderbolt 5 speed conversion

[reedspeed]

I have a 1969 650 Thunderbolt. The bike badly needs a 5 speed transmission to enable it to be run on the Interstate highways here in Florida. What are my options?

Jim,
Vero Beacg, FL

[STAR TWIN]

What exactly is the problem? Is it undergeared for Highway use? If so, a gearbox sprocket with an extra tooth or two would solve the problem.
5 speed boxes (expensive!) generally don't affect top and bottom gear ratios - they just make the jump between ratios smaller.