From the outset in 1921 until the 1960's road production was of horizontal single cylinder design starting with exhaust over inlet overhead/side valve and integral gearbox before settling on overhead valves for both. Most had external flywheels as well. EOI example below, I believe a 500S.

[Linked Image]

There were almost every conceivable design for racing though including the famous 500 V8, water cooled triples, fore/aft boxer twins etc. A wide range of military equipment as well.

Peter (Gambalunga) is the expert on TM though as his late FIL, Duilio Agostini raced them as a works rider.

Richard

2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone