Motorcycle engineer Brian Woolley was one of Britain’s foremost two-stroke engine specialists and is perhaps best remembered for helping to develop the Greeves Silverstone production racer. The unique machine offered here was created by Brian in collaboration with Bob Stevenson and first raced in 1966 by Trevor Burton. It is powered by a 1964 Yamaha YS-1 roadster engine modified by the addition of a water-cooling jacket in the interests of reliability. Tuning work consisted of the usual ‘port job’, fitting an 18mm Dell’Orto carburettor and replacing the rotary inlet valve’s compressed paper disc with a Tufnol part giving longer opening. Small capacity engines with relatively narrow power bands are best served by multi-speed gearboxes (Suzuki’s 50cc RK67 twin used 14 speeds!) and Woolley ingeniously doubled up the Yamaha’s four ratios by using an auxiliary transmission in the form of an American-built ‘Gomatic’ high/low unit, carried on the swinging arm’s left leg. Motor Cycling explained the change procedure when its tester Bruce Main-Smith rode the Woolley Yamaha at the end of the 1966 season: ‘In reality, the rider starts in low and bottom, changes three times on the gearbox to reach top, then shifts into high. Total five. It is not “practical” to run through all eight ratios on the trot but the Gomatic’s half a ratio is useful on hills to get exactly the right cog.’ The modified YS-1 engine was installed in a purpose-built spine-type frame equipped with Suzuki front fork, Bianchi front brake and Itom rear hub. BMS found that the bike ‘steered impeccably and held the road like glue. The brakes were entirely adequate and the gearchange light and neat.’ Completed in the summer of 1966, the Woolley Yamaha with Trevor Burgess aboard had won twice at Cadwell Park, once at Darley Moor and finished second in the Temple 100 in Ireland by the season’s end. Motor Cycling estimated the Yamaha’s top speed to be the same as that of Honda’s CR110 over-the-counter 50cc racer – not bad for a home-built ‘special’. Kept on museum display for the last 15 years, this unique racing ‘50’ is in running condition but will require re-commissioning before returning to the racetrack. The machine is offered with a copy of Motor Cycling’s article and a quantity of spares.
Motorcycle engineer Brian Woolley was one of Britain’s foremost two-stroke engine specialists and is perhaps best remembered for helping to develop the Greeves Silverstone production racer. The unique machine offered here was created by Brian in collaboration with Bob Stevenson and first raced in 1966 by Trevor Burton. It is powered by a 1964 Yamaha YS-1 roadster engine modified by the addition of a water-cooling jacket in the interests of reliability. Tuning work consisted of the usual ‘port job’, fitting an 18mm Dell’Orto carburettor and replacing the rotary inlet valve’s compressed paper disc with a Tufnol part giving longer opening. Small capacity engines with relatively narrow power bands are best served by multi-speed gearboxes (Suzuki’s 50cc RK67 twin used 14 speeds!) and Woolley ingeniously doubled up the Yamaha’s four ratios by using an auxiliary transmission in the form of an American-built ‘Gomatic’ high/low unit, carried on the swinging arm’s left leg. Motor Cycling explained the change procedure when its tester Bruce Main-Smith rode the Woolley Yamaha at the end of the 1966 season: ‘In reality, the rider starts in low and bottom, changes three times on the gearbox to reach top, then shifts into high. Total five. It is not “practical” to run through all eight ratios on the trot but the Gomatic’s half a ratio is useful on hills to get exactly the right cog.’ The modified YS-1 engine was installed in a purpose-built spine-type frame equipped with Suzuki front fork, Bianchi front brake and Itom rear hub. BMS found that the bike ‘steered impeccably and held the road like glue. The brakes were entirely adequate and the gearchange light and neat.’ Completed in the summer of 1966, the Woolley Yamaha with Trevor Burgess aboard had won twice at Cadwell Park, once at Darley Moor and finished second in the Temple 100 in Ireland by the season’s end. Motor Cycling estimated the Yamaha’s top speed to be the same as that of Honda’s CR110 over-the-counter 50cc racer – not bad for a home-built ‘special’. Kept on museum display for the last 15 years, this unique racing ‘50’ is in running condition but will require re-commissioning before returning to the racetrack. The machine is offered with a copy of Motor Cycling’s article and a quantity of spares.
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