Spec Number | Flywheel | Hopper Cooled | Tank Cooled | Industrial | Suction Carburettor |
| A10, A11, A12, A13, A14, A14a, A14c, | Single | Yes | No | No | Yes |
| A50, A51, A52, A53, A54, A54a, A54c, | Single | No | Yes | No | Yes |
| A15 | Two | Yes | No | No | Yes |
| A16 | Two | Yes | No | No | No |
| A18, A20, A23 | Two | Yes | No | Yes | Yes |
| A21, A22, A24, A29 | Two | Yes | No | No | No |
| A26, A27, A28 | Two | Yes | No | Yes | No |
| A55 | Two | No | Yes | No | Yes |
| A56 | Two | No | Yes | No | No |
| A58 | Two | No | Yes | Yes | Yes |
| A60, A63 | Two | No | Yes | Yes | Yes |
| A61, A62, A64, A69 | Two | No | Yes | No | No |
| A66, A67, A68 | Two | No | Yes | Yes | No |
| A117 | Single | Yes | No | Yes | Yes |
| A157 | Single | No | Yes | Yes | Yes |
NOTES:-
1) Industrial Engines from Spec A26 and A66 onwards have the Fuel Tank attached by straps to the crankcase and have Heavy Flywheels.
2) Agricultural Standard engines do not have the fuel tank attached to the engine, and the flywheels are lighter.
3) Engine Rotation is anti-clockwise as standard, viewed with the magneto on the right. The letter C is stamped on clockwise rotation engine plates.
Flywheel | Diameter | Face | Spec Notes | Quantity |
| A74 | 18 inches | 2½ inches | A10 to A14, A50 to A54, A17, A57 | One |
| 2/474 (Replaces A74) | 17½ inches Industrial Engines | 3¼ inches Flat Face | A20, A23,A26 onwards except A29 A60, A63, A66 onwards except A69 | Two |
| B274 (Replaced by 2/474) | 22 inches | 2½ inches | No Spec Information Fitted to few engines | Two |
| A381 (Replaced by 2/474) | 22½ inches | 2¾ inches | No Spec Information Lighting Plant engines | Two |
| A274 (Current fitting) | 18 inches | 2½ inches | A15, A16, A18, A55, A56, A58 A21, A22, A24, A61, A62, A64 and A25, A29, A65 & A69 to date Not used on A117 and A157 | Two |