A motorcycle transmission is an essential component that allows you to control motorbike speed. It uses a series of gears and other parts to transfer power from the engine to the wheels according to the road conditions.
How Does a Motorcycle Transmission Work? Motorcycle transmission works by pressing the clutch lever to disengage the engine from the gearbox. Next, use the gear selector to choose the appropriate gear ratio according to your requirements. Releasing the clutch will engage the engine to the gearbox and transfer the power to the wheels according to the required torque and speed requirements.
This article will guide motorcycle owners regarding the working of the transmission system and its different parts.
Purpose of a motorcycle transmission
The primary purpose of a motorcycle transmission is to provide a mechanism to transfer power from the engine to the rear wheel, enabling the rider to control its speed and torque.
Without a transmission, it cannot provide enough power to propel the motorbike at different speeds and under varying conditions, making it less versatile and less functional.
Moreover, it allows you to change gears according to the power requirements of different terrains. For example, you need more torque and less speed on desert terrain and vice versa on highways.
Therefore, the transmission will allow you to achieve these characteristics by changing from low to high gears according to road conditions.
Parts of a motorcycle transmission
It consists of several essential parts transferring power from the engine to the rear wheel. They include the clutch, gear selector, gearbox, and final drive mechanism.
Several other parts include a set of gears, electronics and instrumentation parts, and drive chains.
Clutch
The clutch is the first component and connects the engine to the gearbox and allows the rider to disengage it from the gearbox when shifting gears.
You can apply it by pulling or pressing the clutch lever, which frees the engine from the gearbox. You will observe a change in the motorbike that sounds like no load conditions.
In this position, the role of the next part, the gear selector, comes into play to allow you to shift gears without damaging the transmission. You will not find clutch or gearboxes in automatic transmissions like CVT and electric bikes.
Gear selector
The gear selector is a mechanism that allows you to select different gears while riding a motorbike. You can easily find it on the lower left side of the engine as a lever pegged at the center.
Pressing forward will change gear ratios in the forward direction while pushing its rear part will reduce the gear ratios. The specific sequence of gears varies according to the motorcycle model and manufacturer.
When you shift gears, the gear selector moves a shifting fork inside the gearbox, engaging or disengaging different gears. Its purpose is to change the gear ratio between the input and output drives.
Gearbox
The gearbox is the heart of the motorcycle transmission. It contains a series of gears that provide different gear ratios, allowing the rider to match the engine’s output to the demands of the road or riding conditions.
When the rider shifts gears, the gearbox engages or disengages different gears, changing the gear ratio and altering its speed or torque.
Higher gears engage the largest gear set in the gearbox causing it to move faster while you accelerate at the same engine rpm.
Final drive mechanism
It transfers power from the gearbox to the rear wheel, resulting in motorcycle movement under different circumstances.
You can also call it the main drive shaft or output drive. According to the model and manufacturer, it can be in various designs and shapes.
Depending on the make and model, it can be a chain, belt, or shaft. For example, the 2021 Kawasaki Ninja ZX-10R has a chain drive, the 2021 Harley-Davidson Sportster Iron 883 has a belt drive, and the 2021 BMW R 1250 GS Adventure has a shaft mechanism as an output drive.
Belt drives require less maintenance than chain drives. While shaft drives are the most durable and require the least maintenance. However, they are also the heaviest and least efficient.
Working of a motorcycle transmission
The working of a motorcycle transmission starts as soon as you press the clutch lever and gear selector to move it from its neutral position. When the engine runs, it generates power to be transferred to the rear wheels.
It is called the neutral position. Pulling in the clutch lever frees the engine from the transmission, and you can only shift gears in this setting.
The next step is to use the gear selector with your left foot. It engages a shifting fork inside the gearbox, which moves a gear into place.
Now you release the clutch lever, and the engine will transfer power to the rear wheel according to the selected gear ratio.
When you want to shift to a different ratio, you have to repeat the process, pulling in the clutch lever, selecting a gear, and releasing the clutch lever.
For most motorbikes, pressing the gear selector in one direction will put it into higher gears, while pressing the other side reduces the gear ratios.
For automatic and electric motorcycles, using an accelerator appropriately selects the correct gear ratio or continuously changes it instead of in discrete steps.
Types of motorcycle transmission
There are 2 main types of motorcycle transmissions, including manual and automatic. Each one has further subtypes based on its working principle and transferring mechanism.
Manual
They require you to shift gears using the gear selector and clutch manually.
Moreover, they have pros and cons according to the rider’s requirements. They have some advantages, like being less complex and easy to maintain.
At the same time, they give you more control to change the gear according to the driving conditions, torque, and speed requirements.
However, you have to engage both hands to operate the motorcycle, which can be a problem for the delivery services-related personnel.
Sequential transmission
A sequential transmission requires the rider to shift gears in a specific order, typically from 1st to the highest number.
You cannot skip or downshift to a lower gear without going through each one in the sequence.
You will find them on low-end routine motorcycles, racing motorcycles, and high-performance sports bikes.
Constant mesh transmission
A constant mesh transmission allows the rider to shift gears in any order.
It uses a series of gears constantly meshing together, allowing the rider to change them without waiting for them to engage.
Therefore, there are no chances of damage to the gear teeth. Constant-mesh designs are the most common manual transmission type on most motorcycles.
Automatic
Automatic transmissions are the latest designs that eliminate the need to shift gears manually.
They use a series of sensors and computer-controlled actuators to automatically shift gears based on its speed and acceleration.
They have advantages like being easier to operate, and also, one-handed operation of the motorcycle is possible.
However, you don’t have control over the gear ratios, and it automatically selects the appropriate one according to the speed.
Dual clutch transmission
It is an automatic transmission that uses two separate clutches for odd and even gears.
When you rotate the accelerator, it preselects the next shift using the other clutch, allowing seamless gear changes.
Clutch activation and gear selection are automatic with the help of hydraulic actuators and sensors.
They are expensive, and you will commonly find them on high-performance and sport-touring motorcycles.
CVT
Continuous variable transmission (CVT) does not require clutch or gear change. It uses a belt or chain drive to provide an infinite number of gear ratios.
Moreover, it can vary the gear ratio continuously based on its speed and acceleration, providing a smooth and seamless ride.
You will find them on scooters and small displacement motorbikes as they can make the engine less fuel efficient because of the lack of control in the rider’s hands. Moreover, there is a delay in their operation when you accelerate the motorcycle.
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