Triumph 1925 SD 550 cc side valve frame # 342239 engine # 103811
The SD (Spring Drive) was in fact a somewhat modernised version of the famous model H, which had grown out of the “Trusty” veteran Triumph. By the mid-twenties belt drive was losing its appeal to many motorcyclists, so Triumph designed a model with chain secondary drive.
The primary chain is protected by a well-engineered aluminium case and runs in an oil bath to minimize maintenance of chain and clutch. The powerful 550 cc engine (bore x stroke =85×97) has lots of torque.
The machine is equipped with three speed Sturmey Archer gearbox, 26×3 beaded edge tyres and Bosch magneto.
There is a full acetylene lighting set on board.
This older restoration SD is an interesting example of a vintage British machine in the popular 500cc class. It’s a good runner.