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Discussion Starter · #1 ·
So im a newbie to motorcyle engines and was wondering after reading a few threads on clutch replacement, how does the clutch actually engage the transmission on these bikes. The clutch is on the far right of the bike and the flywheel is on the inside. i know the flywheel spins with the engine, and when the clutch is engaged, it spins with it, but how is it transferred to the tranny? i couldnt make sense of it from the piks and im one of those engineering students that has to know how everything works:D thanks for clearing it up
 

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the "flywheel" has nothing to do with the clutch. the flywheel is the rotor for the charging system and is on the left side of the engine, where the clutch is on the right.

the clutch basket is driven by the crankshaft by the primary drive gears. the primary drive gear is on the crankshaft. the primary driven gear is on the clutch basket. the crankshaft's rotation is transferred to the clutch basket by this set of gears. there are a series of steel plates and a series of friction plates. one set of plates is slpined to the clutch basket, the other to the clutch hub. the clutch hub is splined to the transmission input shaft. the clutch pressure plate uses spring pressure to hold the two sets of clutch plates together(friction and steels). when the clutch is engaged the frictions and steels mesh together and transfer power from the clutch basket to the clutch hub. since the clutch basket is directly connected to the crankshaft it is always turning as long as the motor is running. since the clutch hub is splined to the transmission input shaft it will always turn at the same rate as the input shaft(or not turn at all when you're sitting still with the bike in gear and clutch disengaged)

when you disengage the clutch(pull in the lever) you're overcoming the springs holding the pressure plate and allowing the frictions and steels to separate, thereby severing the power flow from the clutch basket to the clutch hub.




the transmissions in motorcycles are nothing like those in manual transmission equipped cars. they are a constant mesh design, which i will also be happy to explain if you'd like.
 

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Place the palms of your hands together, very lightly. Twist one hand a little. The other hand doesnt move. Imagine the hand that you're twisting is the clutch drive plate(s) and is attached to the engine..

Press harder against the other hand and it'll start to move. Imagine that hand is the clutch driven plate(s) and is attached to the wheel through the gearbox and chain.

Thats the basic priciple. Two sets of plates (two hands) Pushed tightly together by springs.

In the diagram the basket is the driving hand, turned by the engine through the gear teeth on the outside of it. The slots in the basket engage tabs on the outside of a set of steel plates with friction inserts - the drive plates - and turn those plates with the basket. Between the friction plates are the driven plates, which are plain steel plates. They're slotted on the inside and when they turn they turn the clutch centre which runs through them all. The basket and these plain plates can turn independently of each other.

The diagram doesn't show it very clearly, but the clutch centre sits on the gearbox input shaft and turns that. The pressure plate and springs on the outside does the job of pushing the two sets of plates (your two hands) together tight. When that happens, the basket turns the friction (drive) plates, the friction plates turn the plain (driven) plates, and the plain plates turn the clutch centre.

The clutch lever, via the cable and push rod, pushes the pressure plate away against the springs, just as your wrist can release the pressure holding your hands together.

At some point, there is enough pressure to allow the drive plates to start to turn the driven plates, but if the driven plates resist because of load - like a stationary wheel - pressure isn't enough to turn those plates without slipping. The wheel will start to move slowly and as it does you can increase the spring pressure pushing the plates together (by releasing the lever more on a motorcycle clutch) until eventually all the drive is transferred with no more slip.

Some clutches have the friction material on the driven plates, but the operation is exactly the same. Car clutches usually only have a single plate - you can do this because there's room for a much bigger plate which takes the load on its own. These usually have a release bearing sitting over the gearbox input shaft and operated by a fork instead of a pushrod that has to go right through the shaft, and a single large diaphragm spring instead of a set of coil springs.

In the car the gearbox output shaft is usually concentric with the input shaft and internally a gearbox layshaft has to used to facilitate this, whereas on the bike the shafts are seperated to allow mounting of the chain front sprocket and there's no layshaft in the box.

Rob
 

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Discussion Starter · #5 ·
nice writeup goingtoscotland thats exactly what i was looking for. im so used to the simplicity of manual cars, but its amazing the engineering that goes into bikes thanks for clearing it up, gunna have to do a report on this one for my next class probject..reppd!
 

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the transmissions in motorcycles are nothing like those in manual transmission equipped cars. they are a constant mesh design, which i will also be happy to explain if you'd like.
cars are constant mesh as well...most cars just aren't sequential like a motorcycle transmission.
 

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Explain to me cylinder flame combustion as a function of spray patterns/valve openings and piston surface. THAT is voodoo magic to me...
 
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