timing gears of a four-stroke engine Instead of toothed belts or a chain, 10 spur gears are used to drive the injection pump, the camshaft and the ancillaries. Injection pump and camshaft turn with half the crankshaft speed. description ordernumber 479 see also: 7-cylinder radial engine flat engine double-cylinder Stirling engine two stroke engine with diaphragm timing and control cylinder