Rigid & Plunger A Group, S/arm A & B Group and all 4 speed C Group

This design covers five gearboxes that are based on the ‘Plunger A10 Gearbox’ with minor variations to the cam plate pivots, gear selector mechanisms, cam plate plungers and casings. The change to various parts of the plunger A group gearbox (mainly the gears) took place after engine number ZA10 1214 (1950 650cc) and engine number AA7 101 (1951 500cc). These gears are not interchangeable.

The B group changed from a 1/4 wide rear chain to a 3/8 wide one in 1958. If in doubt as to which sprocket to use, look at the rear wheel sprocket.
Although the C10L/12 gearbox is of a similar design to the others, most of the parts are different.  The gears however are of a different design, so the illustration is not accurate.

N.B. All parts are listed but are not necessarily available, click on a part number for current availability.