In the mid-1960s I rode a traditional British 500 pushrod single for a few months and intimately felt the role of flywheel mass. Such singles were described in their era as ‘firing at every telegraph pole’, and the rider was very much aware of it. Combustion in a four-stroke single delivers energy for about 100 degrees out of every 720, or 14% of the time. During the other 86% of the time, the bike is powered by the flywheels. This means that actual crankshaft rpm, displayed on
