Sequential gearbox

Nearly every geared motorcycle sold in India, from a Splendor to a Himalayan, uses a constant-mesh sequential gearbox built into the engine cases. It works like a car's manual in principle, gear pairs on two shafts with the chosen pair locked to a shaft, but the selecting mechanism is different and simpler.

• The clutch lever on the handlebar disconnects the engine. Most bikes use a wet multi-plate clutch running in the engine oil.
• The foot lever turns a shift drum by one notch. The drum is a cylinder with zigzag grooves machined into it.
• Shift forks ride in those grooves, so each notch of the drum slides one fork sideways.
• The fork pushes a sliding gear along its splined shaft until dog teeth on its face slot into the neighbouring gear, locking that ratio. There are no synchronisers; the dogs simply engage, which is why a quick, positive shift works better than a lazy one.
• Drive leaves the output shaft through the front sprocket, by chain to the rear wheel.

Because the drum can only rotate one notch at a time, gears can only be selected in order: 1-N-2-3-4-5-6, with neutral tucked between first and second. A commuter typically has four or five speeds; sport and touring bikes have six. Honda's Gold Wing has a seven-speed dual-clutch version of the same idea.

What you notice: a definite click at the foot, the usual pattern of one down and the rest up, the need to find neutral at a standstill, and the fact that shifting up without the clutch is possible, which is what a quickshifter automates on bikes like the Apache RR 310 and KTM 390 Duke.