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Just like the transmission, the clutch plays a crucial role in making your motorcycle run.
But why do you need a clutch?
What does it consist of?
And what is the “clutch friction zone” anyway?
Tune in to discover:
- Why you need a clutch at all
- 3 common clutch component
- What the “clutch friction zone” is
Hello, and welcome to another episode of 30-minute motorcycling – a podcast for those riders who are at the beginning of their own Dual Wheel Journey, where you’ll discover something new about how your motorcycle, moped, or scooter works – in less than 30 minutes.
And in the previous episode, we talked about motorcycle transmissions. As I promised, it’s now time to talk about and demystify the clutch – specifically, you’ll discover why you need it, what it consists of, and while we’re at it, why not finally explain what the “clutch friction zone” is.
There’s a lot to go through and digest, so first, let’s talk about what the clutch does.
To change gears, the engine has to be disconnected from the rear wheel. Otherwise, the only way to change gears would be to come to a complete stop – something which would be fine for the first or maybe second gear, but not so much for any higher gear.
Have you ever tried to pull away from a standstill in fourth gear?
So how can you disengage and reengage the engine from the rear wheel?
Here’s where the clutch comes in – while it’s engaged, power from the engine to the rear wheel is temporarily disengaged so you can change gears.
Of course, the engine’s still running – it’s just not delivering power to the rear wheel while you squeeze in the clutch.
Most bikes have clutches that are cable operated, which is easy to maintain. However, some motorcycles from KTM and Husqvarna have clutches that are hydraulically operated.
Similar to a hydraulic brake system, a hydraulic clutch system uses fluid to operate the clutch – meaning that the clutch doesn’t feel as stiff when you squeeze the clutch lever.
But there’s a catch – and that catch is that a hydraulic clutch is more expensive to maintain since you have to buy the fluid separately and replace it every 2 years.
If you’d like to know more about cable vs hydraulic clutches, I’ve put a link in the show notes to a video from the Motorcyclist Magazine YouTube channels about the topic.
But either way – what’s inside a clutch that makes it possible to disengage the engine from the rear wheel?
Aside from the clutch hub, a typical clutch consists of 3 parts:
- The clutch plates
- A diaphragm or a set of coil spring
- And a clutch housing
The clutch plates sit between the housing and the clutch hub and come in two types – “friction” and “steel,” along with a pressure plate.
The smaller your clutch is, the more plates it will have.
The friction and steel plates alternate between one another – so if you’ve got four friction plates, you’ve got four steel plates as well.
Along with the friction and steel plates, there’s also a pressure plate.
If you engage the clutch, this pressure plate separates the friction and steel plates.
When you disengage the clutch, the friction plates press the clutch hub against the flywheel which transfers the power to the transmission.
While the clutch is disengaged, the clutch plates are pressed together through either a set of coil springs or a diaphragm spring.
For motorcycle clutches, a coil spring setup with between 4-6 springs is the most common – although there are a few that use a diaphragm spring – similar to the kind most cars use.
And before you ask, it’s called a “diaphragm spring” because the shape of the spring resembles a diaphragm.
And finally, the clutch housing holds all of the components together – and that’s about it.
And since we’ve talked about the clutch, now’s a good time to mention what the clutch friction zone is, and what happens when you find it.
Unless you’re riding a scooter with a CVT transmission or a motorcycle with an automatic or even a semi-automatic transmission, you may have noticed that as you ease off the clutch lever, the bike will start to move slowly – even though you’re not rolling on the throttle.
But when you let go of the clutch without rolling on the throttle, the engine stalls. Why does this happen?
Here’s where the clutch friction zone comes into play.
The “clutch friction zone” or just “friction zone,” refers to the point where the engine and the rear wheel start to connect.
And when they start to connect, the engine will partially transfer power to the rear wheel – this is why the bike will start to move slowly once you find the clutch friction zone.
There you have it – now, the clutch and the clutch friction zone have both been demystified. So now, you’ll know what the clutch does and what happens when you stall the engine.
If you’d like to read more about motorcycle clutches, including how long they tend to last, and the difference between wet and dry clutches, I’ve included a link in the podcast episode description to a blog post on The Dual Wheel Journey about it.
Until next time, keep your helmet on and your eyes on the road. Bye!