BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: Mikey82 on 06 Aug, 2026, 19:19

Title: Sprockets
Post by: Mikey82 on 06 Aug, 2026, 19:19
I have a 19 tooth sprocket on the front and 42 on the rear
Rather than have to remove primary side clutch etc, could i change the rear sprocket to increase or decrease the number of teeth to reduce the higher revs in top gear.
Anyone done this?

GF swinging arm model 1963
Title: Re: Sprockets
Post by: neil1964 on 06 Aug, 2026, 22:21
If you want to raise the gearing (ie less engine revs per mph) then you need a smaller rear sprocket. Afaik 42T is smallest. If your speedo is right now then messing with rear sprockets will alter this.
Most people alter the engine sprocket as it does not affect speedo. Yes you have to remove primary cover and undo the cush drive but adding one or two teeth and extra link on primary is probably best option.