i have a 1952 plunger roadtest from the motor cycle [weekly]. it suggests that manual advance was fitted to manage the revs using pool petrol from that period in time. the star twin was classed a sports machine that needed knowing to get the best engine performance. it was fitted with a long levered adv/retard lever on the left handlebar.for 1950/51 it had 7.2 =1 compression pistons and top speed 92mph. 1952 may have had higher compression pistons ?
