Types of Motorcycle Transmission

Manual Transmission:

Most manual transmission two-wheelers use a sequential gearbox with five or six gears to shift into using a foot lever. The clutch lever on the left side of the handle-bar operates the clutch. On a traditional motorcycle, a five-speed configuration would be known as "one-down, four-up" or "one-up, four-down" based on the manufacturers’ preferred shifting pattern, all in relation to the neutral gear.

The neutral gear is found "half a click" away from first and second gears, making it possible for the rider to shift to either first or second gear directly from neutral, but higher gears may only be accessed in order, hence the name “sequential”.

With modern performance motorcycles, a much simpler form of the same is installed in a race-style cassette transmission. Here, the crankcase will be designed with a cavity to accommodate a single gearbox unit that slides into it rather than being installed between the two case halves. This design allows the transmission to be removed and replaced with the engine still in the frame so it can be serviced quickly and easily that also allows playing with the gear ratios.

Inspired by MotoGP, Kawasaki has equipped its H2 series of monster performers with planetary gears (commonly known as epicyclic gear train) that has its in-line shafting and cylindrical casing. It is often recognized as the light alternative to conventional pinion-and-gear reducers. The dog-rings are lighter than traditional transmission gears and offer significantly lighter shift effort, facilitating quicker acceleration.

Automatic Transmission:

Mostly found on scooters, the automatic transmission is trickling down to custom cruisers and exotic sports machine with Honda been a pioneer in developing new forms of gear and clutch designs. Nonetheless, they gave automatic a new meaning to the two-wheeled world and were preferred mainly for their ease of use and decent performance for a very limited run. It became an excellent option for urban commuters, millennials, and casual riders.

1. No shift automatics / CVT

Famously known as CVTs (Continuously Variable Transmissions), it was introduced into mass production by Honda in 1973. You twist the throttle, and you are set to go. No shift lever, no neutral, no reverse, and no leg pulls/push.

The CVT has three parts to it – two conical pulleys, a centrifugal clutch, and a belt. As the engine rpm increases, the centrifugal clutch pushes the belt onto one of the conical tapered pulleys, and this causes the wheel to rotate. The speeds depend on the position of the belt on the conical pulley.

The faster the engine revolves, the more of the clutch is displaced, and this pushes the belt to a higher section of the conical pulley. As a result, accelerating with a CVT is an incredibly smooth, uninterrupted process.

All scooters available in the market are currently running on the CVT transmission, and every brand has its variations of the same. Of course, there are other players like Aprilia Mana and BMW’s C range of two-wheelers using this tech.

2. Dual clutch manumatics

Preserved for the four wheels, this piece of technology was brought into the biking world, again by Honda with their VFR1200F sport touring motorcycle in 2010. The engineers at Honda managed to take the Formula One-derived transmission and put this into the confined spaces of two wheels and make it change gears without any interruptions.

The DCT (Dual Clutch Transmission) uses two clutched instead of one. You get one for odd gears and one for even gears with benefits such as rapid and smooth shifting, genuine compression braking, and a stall-proof operation.

The thumb-operated shift controls negate the discernible clutch grab that would otherwise give the distinctive driveline lurch. This will also provide eminent fuel economy along with the ease of use and convenience and give motorcycles, especially the heavy ones, a reverse gear as well to crawl back from spots.

Honda’s DCT technology is now in its tenth year of production and gaining popularity year on year, having sold over 100,000 DCT equipped motorcycles ever since. Currently, Honda is running the maximum number of models with this transmission including the VFR1200 series, CRF 1000L Africa Twin, NC750X, CTX700 and the Gold Wing.

3. Centrifugal clutch designs

There is a surprising story behind Honda developing the unique automatic centrifugal clutch for its Cub series. The goal was to produce a bike that could be operated one-handed, as at the time, restaurant deliveries were made by bicycle riders carrying boxes with their right hand while steering with their left. The result was the birth of the revolutionary automatic centrifugal clutch.

They are not automatic in a true sense. This kind of system will allow the rider to manually change the gear with the push/pull of a leg, but there is no handlebar-mounted clutch lever. Also called as auto-clutch, they are predominantly found in all-terrain vehicles and entry-level dirt bikes.

This system allows the rider to stop and move in any gear and is activated only when the engine rpm increases from an idle situation. As the engine rpm increases, the centrifugal clutch pushes the steel shoes and then the driveshaft. Such a mechanism wears out sooner than others, especially in a stop/go urban traffic commute.

This clutch was seen mostly on all scooters and bikes you get in South East Asian countries like Vietnam or Thailand. Centrifugal clutches are also majorly used on go-karts, snowmobiles, and other vehicles of conveyance. BMW uses this on their K 1300 range of motorcycles as well.

Electric motors

Time and again, it has been proved that electric/hybrid vehicles have an overwhelming advantage, especially to ride within the town, and this evolution has been a gradual process for some – and an exciting start for others. With stalwarts like Harley Davidson, Indian, BMW and all significant auto-makers having electric powertrain technology in the pipeline, the future is going electric.

With a simple battery-motor principle, there is not much complexity regarding the number of parts used. The compact direct drive mechanism allows the electric motor to spin to all its glory with inputs from the throttle, just like in CVTs’. The added advantage here is that electric motors have instant torque and are much quicker than the CVTs’.

This is the simplest form of auto transmission one can see on a two-wheeler, and the manufacturer can have multiple iterations of the same principle. They can either opt for a single-drive setup or add gears for optimum control options.

Source: SuperBike