Motorcycle Transmissions & Parts

The majority of modern motorcycles use manual sequential gearboxes with five or six gears. “Sequential” means that the rider cannot select any gear any time. He or she has to pull up a shifting lever to select one gear higher or press it down to change gear from higher to lower in strict order. As standard, the shifting lever is positioned on the lower left side of the bike to be operated by the rider’s left foot. A clutch lever is located over the left grip so that the rider can operate the bike without taking his or her hand off the handlebars.

In a traditional “1 down 4 up” or “1 down 5 up” scheme, the neutral gear is positioned between the first and second gear because it makes the most sense. That way, by pushing the lever down several times, you know that you have reached the first gear and to put your bike in neutral, you have to pull the lever half a click up. From the neutral position, you can select the second gear when starting downhill. The construction of sequential motorcycle transmissions allows experienced riders to use the clutch only when starting from a complete stop while performing clutchless upshifting between higher gears.

Since the conventional manual gearbox with an H-pattern of shifting used in cars is too large to be fitted into a compact motorcycle frame, and shifting using hand lever on bikes is proved to be impractical, modern motorcycles use a compact “dog clutch” scheme where all of the gear teeth are always engaged. Some of the gears are connected to input and output shafts through splines but can shift from side to side. Some of them rotate freely. When the rider pushes the shift lever, it rotates the shift drum or barrel through a ratchet mechanism. The drum has grooves around its surface used to actuate shift forks.

As the drum rotates, these forks literally shift gears on transmission shafts to engage the needed gear pairs, thus the term ""shifting gears."" The engagement between freely rotating gears and those splined to the same shaft is performed through dog clutches. Some gears have pegs on their sides called “dogs.” They are designed to nest in corresponding recesses on adjacent sprockets. To complete the shift to an adjacent gear, you need to provide only a brief interruption of engine torque. A shift fork makes neighboring gears lock together and rotate as one. By pushing the shift lever up without clicking it, you can synchronize the rotation of two gears, which allows you to shift them after rolling off the throttle without disengaging the clutch and without causing damage to transmission components.

A smoothly running gearbox is essential for your success on the track or comfort on the road. If something goes wrong with the gears, you can tell with certainty that the problem is in the transmission. When it is time for repairs or upgrade, visit our online store and browse the catalog of motorcycle transmissions and components where we’ve gathered only high-quality products made by some of the most reputable manufacturers in the industry. We offer high-performance gearboxes with additional overdrive gears. Some models feature rear gears, which is convenient if you own a heavy cruiser. Here you can find rebuild kits, replacement shafts, gear, shift forks, drums, transmission covers, and much more.