| Manufacturer | BSA |
|---|---|
| Also called | BSA A50, Cyclone |
| Production | 1962-1970 |
| Predecessor | BSA A10 |
| Engine | 498cc air cooled twin |
| Power | 33bhp @ 5800 RPM |
| Transmission | four speed gearbox to chain drive |
| Wheelbase | 54.75 inches (139.1 cm) |
| Dimensions | L 81 inches (210 cm) W 11.7 inches (30 cm) |
| Fuel capacity | 4 gallons |
The BSA Royal Star is a British motorcycle that was a radical new design for BSA that paved the way for a whole range of very successful unit construction twins. As well as giving a clean look to the engine, with the pushrod passages part of the cylinder block casting, unit construction reduced the number of places oil could leak from.
Bob Fearon, Managing Director and General Manager of BSA recognised the need for a completely new look that built on the best features of the A10's but would succeed in the potentially lucrative but competitive US market. Working with Chief Development Engineer Bert Perrigo they developed the unit construction Star twins. Launched in 1962 the as the 500cc BSA Star and later the more sporty Royal Star The model was widely exported to the USA and Australia as well as becoming a top seller in the UK in the early 1960s.[1]
The Royal Star had a relatively small single Amal monobloc carburettor, and later Concentric carburettor, but in 1964 new pistons and a new gearbox improved performance. The machine had a top speed of about 90 mph and was relatively free of vibration. Sharing common engine and cycle parts with the larger BSA A65 Star 650 twin, it was an over-engineered machine and proved very robust. The only major fault with the engine design was a plain crankshaft bearing on the timing side which, when worn, would cause a drop in oil pressure. In 1965, BSA addressed the bearing issues with a roller bearing on the drive side, as it had been on the pre-unit engines, with an improved bronze bushing on the other end.[2]
Bacon, Roy "BSA Twins and Triples"