The best way to understand how your motorcycle's transmission works is to ride a bicycle. Why? Because on a bicycle, you’re the engine, and you feel how the load on the engine changes as you shift gears.
Motorcycle transmissions (the most common manual-shift kind) use pairs of gears moving laterally on a pair of shafts to change the ratios between the engine and the rear wheel. Pushing the foot-shift lever pushes or pulls these gear pairs into or out of engagement. Here are some of the principal parts, and what they do.
PRIMARY DRIVE Power from the engine’s crankshaft flows into the engine through these gears or chain.
CLUTCH Couples or uncouples engine power to
input shaft.
SHIFT LEVER Used to change gears.
SHIFT DRUM Converts the up-and-down motion of the gear shifter to the shift fork's horizontal motion.
SHIFT FORK Moves gear pairs into and out of engagement horizontally on shafts.
INPUT SHAFT Power flows through this shaft to a selected gear pair and then out through the countershaft.
GEARS Multiply force from the engine.
DOGS Gear pairs slide laterally on their shaft, and the dogs connect adjacent gear pairs.
OUTPUT OR COUNTERSHAFT The power-out shaft.
FINAL-DRIVE Connects the transmission to the rear wheel. Usually a chain, but can also be a driveshaft.
The best way to understand how your motorcycle's transmission works is to ride a bicycle. Why? Because on a bicycle, you’re the engine, and you feel how the load on the engine changes as you shift gears.
Motorcycle transmissions (the most common manual-shift kind) use pairs of gears moving laterally on a pair of shafts to change the ratios between the engine and the rear wheel. Pushing the foot-shift lever pushes or pulls these gear pairs into or out of engagement. Here are some of the principal parts, and what they do.
PRIMARY DRIVE Power from the engine’s crankshaft flows into the engine through these gears or chain.
CLUTCH Couples or uncouples engine power to
input shaft.
SHIFT LEVER Used to change gears.
SHIFT DRUM Converts the up-and-down motion of the gear shifter to the shift fork's horizontal motion.
SHIFT FORK Moves gear pairs into and out of engagement horizontally on shafts.
INPUT SHAFT Power flows through this shaft to a selected gear pair and then out through the countershaft.
GEARS Multiply force from the engine.
DOGS Gear pairs slide laterally on their shaft, and the dogs connect adjacent gear pairs.
OUTPUT OR COUNTERSHAFT The power-out shaft.
FINAL-DRIVE Connects the transmission to the rear wheel. Usually a chain, but can also be a driveshaft.