Gearing - gearbox sprocket teeth

I had a '72 Commando 750. When purchased, it had been fitted with a 24 tooth gearbox sprocket, which was far too large. I changed down to 22 teeth, which was far better, and was fine for road use, however too high a gearing to obtain max revs in top gear. Probably a 19 tooth sprocket would result in better acceleration, but too high an engine speed (and fuel consumption) for fast cruising. A 20 tooth is probably the best compromise.

I agree with John. When I first had my Commando back in 1975 it had a 19t sprocket on and accelerated like the clappers. I have a 22 on now which gives 70 MPH at about 4200rpm. (twin Jim Schmitt flatslide carbs and a pw3 cam) The mistake I made at the time was to have the ports opened up to 32mm, 30mm is the way ahead for a slick 750 on the road. The original Interstates were fitted with a 21T sprocket as standard for touring.

MyMk3 850 had a 20T g/box sprocket fitted when Igot it from the Kenya police - geared for good acceleration on presidential motorcade duties, but found it not good fornormal road workespecially on thelonger journeys with sustained high revs at cruise. Changed to a 22Twhichprovided much more practical gearing.