Constant Mesh Type Gear Box : Most of the gearboxes on motorcycles are "constant mesh". That means all the gears are constantly meshed with one another and are always spinning. The four/five gear constant mesh type gearbox is employed in Hero Honda Motorcycles.
In the motorcycle gearbox, there are two shafts, the one with the clutch on its one of the ends is the main shaft and the other is the countershaft and it has the countershaft sprocket on one of its ends.
Some of the gears are fixed and/or machined on the transmission shafts. The other gears slide or spin on these shafts. The gears that slide back and forth on the shafts are called Dogs. These Dogs are knobs of metal that fit into holes in the gears beside them, locking the two gears together. The sliding gears are moved back and forth by Shifter Forks which in turn are moved by a shifter drum. The Shifter Forks are usually attached to the Shifter Drum or move in a groove machined in the Shifter Drum. This drum is turned or rotated through different styles of linkages, by the gear Shifter Shaft. As the gears move back and forth they lock the main shaft and counter shaft together through each set of gears, giving us different gear combinations, e.g. 1st, 2nd, 3rd, etc.