Hi my gs750 77 runs standard sprockets 15-41 630. But is seriously under geared, I can cruise around town in 5th almost down to walking pace & still pull away and when out on the open Rd it is so painful cruising at 60mph it is screaming it's head off! So I've gone to 16t on front it helps but not changed much. Is it possible that the gearbox has gears from another model : smaller engine with different ratios?