I picked up on Sonny's mention of a positive stop mechanism. Fred Willingham used one on his early sprinters, they were fitted to kneeler type machines as changing gear with the right foot was not as sensitive as the left hand, and changing gear on a kneeler with handlebar controls could be downright dangerous! Positive stops were fitted to both Triumph and Norton machines particularly those models with separate gearboxes. They simply prevented the selector mechanism passing through more than one gear at once.
A few motorcycle sprinters use air shifters but not that many.
A properly set up gear change linkage and a spider without rounded off lugs will ensure fast changes without too many mistakes! Most scooter sprinters don't bother using the clutch when changing up to third and fourth gears.
