1938 TYPE 438
There was a new four-cylinder engine for the 1936 model year, but it was a flop. Called the ‘upside-down’ engine because the exhaust valves were now on the top, it looked ugly and the high exhaust pipe needed a steel guard to stop it burning the rider’s leg, so for 1938 the Model 438 reverted to the original overhead inlet/side exhaust configuration. The cylinders were now cast in pairs – testing proved that eliminating some of the air gaps between cylinders allowed the heat to be pulled into the airstream more quickly. The aluminium cylinder heads were detachable with the valve mechanism fully enclosed and automatically lubricated. There was a streamlined muffler to keep things quieter on this 95mph motorcycle. Although a left-hand throttle and right-hand gearshift was standard, a right twistgrip and left gearshift was a factory option.