The majority of motorcycles feature a sequential transmission, meaning that to reach the top gear you have to go through all of the other gears in sequence. You control the transmission by moving the shift lever with your left foot. The typical shift pattern of motorcycle transmissions is “1 N 2 3 4 5 (6),” which means the first gear is down while the others are up. (Neutral is between first and second gear).
Although manual transmissions are still prevalent in the motorcycle industry, more and more automatic bikes are coming on the market.
If you want to find out how a motorcycle transmission works, this post is for you. We at PowerSportsGuide have compiled the basics on this topic into one post.
Without further ado, check out this super informative video from MC Garage!
What is a Transmission on a Motorcycle?
Motorcycle transmissions are designed to change the drive ratio between the crankshaft and the driven wheel. In other words, the transmission adjusts engine power based on the rider’s needs. Unlike cars, in motorcycles the transmission is completely integrated into the engine and is often lubricated with engine oil. This part is a must on any bike, as their engines crank out a ton of power, which has to be controlled before it reaches the rear wheel.
(The transmission is often referred to as the “gearbox.”)
Surprisingly, the first motorcycles were manufactured without transmissions. This was possible because these vintage machines only produced a couple of HP and topped out at 20-25 mph.
According to CycleWorld, the first motorcycle transmissions appeared in the early 1900s, and the majority of bikes were manufactured with two and later three-speed transmissions.
But over the years the performance of motorcycles has significantly increased. To handle more engine power, 4-speed gearboxes became more prevalent on European and British motorcycles starting in the 1930s.
What Kind of Transmission Does a Motorcycle Have?
It’s safe to say that most mass-production motorcycles still have manual transmissions. However, you can also find some automatic bikes on the market. The majority of manual motorcycles feature a sequential transmission. This means you have to pass through all the gears before reaching the top gear. Most of these transmissions feature five or six gears, but a few small-bore bikes come with 4-speed transmissions.
Are you wondering how a motorcycle transmission works? Keep reading!
How Does a Motorcycle Transmission Work?
From the outside, a motorcycle transmission works in a very simple way. There is a little gear pedal on the left side of the engine, which is also known as the “gearshift lever” or “toe shifter”. If you pull the clutch and press this lever down with your left foot, you can shift into first gear. If you want to shift into higher gears you just move this lever up. (Or, at least on the majority of the bikes as on certain models you can find all the gears up or down.)
Now let’s get down to the nitty-gritty and see what’s happening inside the motorcycle transmission!
If you take a look into the transmission, you can see a bunch of sprockets sitting on a pair of parallel shafts (called gear shafts).
The input shaft is driven by the crankshaft, which means this shaft is constantly spinning when the engine is on. Or, to be more precise, it only rotates until you pull the clutch lever!
This is because the clutch is mounted between the crankshaft and the transmission, allowing you to start or stop the input shaft from rotating.
In contrast, the output shaft is stationary when the bike is in neutral. As its name implies, this shaft protrudes out of the engine and with good reason.
This is because on the end of this shaft you can find the drive sprocket (or the driveshaftif the bike features a shaft drive). This sprocket turns the chain that finally propels the rear wheel.
Back to the transmission, the two gear shafts sit side-by-side, and the gears on them are meshed together.
Some of these gears can rotate but stay in place on the shaft, while others can move side-to-side as well.
These moveable gears on the shafts are shifted by the shift forks, which are also connected to the grooved shift drum.
There is a little pin on the end of each shift fork that runs in a dedicated groove in the shift drum.
You can control the shift spindle with the shift lever, which moves the drum and eventually the gears.
Phew! Are you confused?
Let’s move on and see what actually happens when you start the engine!
Inside the engine, the pistons start to drive the crankshaft, which transmits power to the input shaft through the clutch assembly. At this moment, the output shaft is still stationary.
To put the motorcycle in first gear you have to move the shift lever down. When you do this, you actually rotate the shift drum slightly inside the transmission, which causes the forks to move.
Finally, the moving forks shift the required gear in the right direction. This is the reason why it’s called “shifting gears”!
On the sides of these movable gears, you can find a few small pegs. When these pegs (also called “dogs”) attach to the neighboring gear, the two gears engage and start to rotate the output shaft.
Since the drive sprocket is mounted on the end of this shaft, it starts to move as well and transmits the power towards the rear wheel.
Each gear delivers a different amount of power, which results in different speeds on the motorcycle.
Here’s a great animation showing how a motorcycle transmission works:
Why Do Motorcycles Have Manual Transmissions?
The four main reasons why motorcycles have a manual transmission are as follows:
- Most riders love to shift.
- Offers more control over the bike.
- Manual transmissions are lighter, smaller, and cheaper.
- Less complex design, easier fix and maintain.
Let’s face it, for many riders shifting is part of the fun, as manual bikes are always far more responsive and provider much better control over the machine.
If your bike features a manual transmission, you can leave it in a lower gear and ride hard. Or, if you just want to cruise around, you can simply use a higher gear for low RMPs.
What’s more, you can downshift anytime for more power or to use the engine to brake.
Another key advantage of manual motorcycle transmissions is their smaller dimensions and lower weight. Manufacturers want to keep bikes as lightweight as possible, which is why they stick to manual gearboxes.
On top of that, manual transmissions feature a far less complex design, which results in cheaper and easier maintenance and lower price tags.
Motorcycle Transmission Maintenance
How do You Check a Motorcycle Transmission?
Just like any other part of the bike, the gearbox can also go wrong in many ways. If you feel there is an issue with your bike, it should be inspected immediately. The best ways to check a motorcycle transmission are as follows:
- Listen to how it sounds.
- Take a test ride.
- Do a dyno test.
- Visually inspect it.
Let’s take a closer look at each in detail!
How Do You Know if Your Motorcycle Transmission is Bad?
If you can hear troublesome noises coming from the engine, it could easily mean that your motorcycle’s transmission is bad. Besides the noises, hard shifting or poor performance can also be a clue to transmission issues. Another common symptom of transmission failures is if you can hardly find neutral or it pops out of the gear.
That’s why you should always “listen” to your bike.
Excessive wear on the gears often leads to “gear lash” and space between the gears’ teeth. These issues often cause strange sounds, especially during shifting.
Besides gears, many other parts can go wrong in a gearbox. Shift forks are prone to bending, but even the shift drum can be damaged too.
If the pockets and dogs on the gears are worn out, it causes the bike to pop out of gear. This mainly happens under heavy loads when you accelerate aggressively or use the engine brake.
This means you can also check a motorcycle’s transmission by doing a test ride. Most transmission failures are noticeable through the shift pedal.
If you can’t test ride the bike for some reason, you can still put it on the dyno.
Unfortunately, in some cases, the only way to thoroughly inspect a motorcycle transmission is to disassemble the engine and visually check the parts.
If the internals are in bad condition, you will probably have to rebuild or even replace the gearbox.
Unless you’re an experienced mechanic, it’s recommended that you leave it to the professionals.
How Much Does It Cost to Repair a Motorcycle Transmission?
It’s hard to tell how much it costs to repair a motorcycle transmission, as it depends on many factors like the severity of the failure, the type of bike, and the cost of labor at the shop. But in most cases, fixing transmission failures is not cheap. If you’re looking for a ballpark figure, a complete rebuild may cost you $1,000-$3,000, or even more. (Again, it’s affected by countless factors.)
Because of the high prices of rebuild kits and labor costs, many owners consider a motor swap, especially on older machines.
In most cases replacing the engine is cheaper and much easier to manage by yourself than rebuilding the transmission.
Why are The Gears Hard to Shift on Your Motorcycle?
Hard shifting on a motorcycle is typically caused by the afore-mentioned malfunctions. Corrosion, wear, damage, or misalignment in the gearbox can make shifting hard or even lead to other serious aftermaths. Besides these issues, there could be many reasons why the gears are hard to shift on a bike. Let’s see what these exactly are!
- Shift pedal malfunctions (the pedal and the pawl return spring can go wrong as well)
- Clutch malfunctions (settings, drag, broken clutch lever)
- Cable problems (drag or cable tension)
- Chain issues (chain is dirty, tension issues)
- Cold engine (this can be a problem especially in cold weather)
- Size of the machine (if the bike is too small for you)
- Lack of shifting experience
- Poor transmission design
Would you like to shift like a pro? Keep reading!
How do You Make Your Motorcycle Shift Smoother?
In a nutshell, the best ways to make your motorcycle shift smoother are as follows:
- Improve your shifting skills.
- Warm up the engine properly before each ride.
- Inspect and adjust the clutch, clutch lever, and cables if needed.
- Make sure the shift pedal and the pawl return spring work properly.
- Clean and lubricate the chain, and adjust its tension if needed.
- Change engine oil (or transmission oil if it’s lubricated separately).
- Inspect the gearbox and fix it if necessary.
Keep in mind that the design of motorcycle transmissions varies from one model to the next. Some models offer a smooth shifting experience while others are harder to shift.
As an example, when you’re shifting on a Harley you can feel when its transmission is shifting through the gears.
In contrast, Japanese bikes typically feature much smoother transmissions. Yamaha in particular stands out from the crowd with its legendary transmissions.
Consequently, you can’t expect the same shifting experience on every bike, as it’s always dependent on the make and the model.
How Often Do You Change Motorcycle Transmission Fluid?
It’s a lesser-known fact that the transmission on certain motorcycles is not lubricated with engine oil. And just like engine oil, the fluid in these transmissions also has to be changed periodically. How often? The general rule is that you have to change the transmission fluid on a motorcycle after every 10,000-25,000 miles or once every one (or sometimes two) years depending on the model. The exact service schedule is always clearly stated in the owner’s manual, which all owners are advised to follow.
It’s commonly thought among riders that motorcycle transmissions are lubricated with engine oil. Well, that’s only partially true!
This is because the transmission of some motorcycles is separated and lubricated with a different liquid than engine oil. Some of these motorcycles are Harley-Davidsons, BMWs, or MotoGuzzis, which transmissions require a scheduled oil change.
Even if manufacturers specify a less frequent service interval for these bikes, many owners replace the transmission oil every year.
Annual maintenance is a must on every motorcycle, and changing this oil as part of it is not a big deal.
If you have a bike and its gearbox is lubricated with engine oil, you don’t have to worry about this. When you change the engine oil this means you change the oil in the transmission as well.
As a takeaway, we’ve listed the most common questions about motorcycle transmissions with the shortest possible answers.
Do motorcycles have transmissions?
Yes, it’s safe to say that all gas-powered motorcycles feature some kind of transmissions. Motorcycle transmissions can be manual, semi-automatic, or fully automatic depending on the make and model.
What is a transmission on a motorcycle?
The transmission on a motorcycle is one of the main parts of its engine, designed for adjusting the engine power. To do this, transmissions feature a set of gear ratios to provide different torque and engine speeds.
What kind of transmission does a motorcycle have?
Most motorcycles feature manual sequential transmissions, which means you have to go through all the gears when shifting to reach the top gear. But it’s good to know that automatic motorcycles are also available on the market.
How does a motorcycle transmission work?
Motorcycle transmissions feature a bunch of gears mounted on two parallel shafts. The input shaft is driven by the crankshaft while the output shaft protrudes out of the engine and rotates the chain. When you put the motorcycle in gear, the input shaft starts to rotate this output shaft, which transmits power towards the rear wheel. The power delivered by the output shaft depends on which pair of gears is engaged. Riders can control these gears with the shift lever to reach the desired speed or acceleration.
Why do motorcycles have manual transmissions?
Manual motorcycle transmissions are smaller, lighter, cheaper, and far less complex than automatic transmissions. Another important factor is that riders love to shift, as manual transmissions are always more responsive and offer more control of the bike.