Selector fork (shift fork)

A selector fork or shift fork is a forked lever inside the gearbox. Its tips sit in a groove in a sliding gear, and its pin runs in a track cut into the rotating shift drum. When you press the gear lever, the drum turns one step and the tracks move the forks sideways, sliding gears so that their dogs engage the next gear.

Most motorcycle gearboxes have three forks. Worn or bent forks cause gears to jump out under load, missed shifts or false neutrals. Bending often follows forceful or half-done gear changes, or a crash on the gear lever.

Shift deliberately and fully, keep clutch free play correct, and change gearbox oil as specified. Replacing forks requires splitting the crankcase on most bikes.