Post by anon on Feb 1, 2007 20:10:10 GMT
From: rowlf Sent: 11/09/2002
Note: This applies to all bikes with a 'wet' clutch, not just the Diversion.
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An apparently sticky clutch and an excellent and very informative answer from RogerD.
If you experience the probems described it is worth pulling in the clutch a few times before engaging gear to exercise the clutch and reduce drag caused by vacuum. Alternatively pull the clutch lever in and wait a minute or so. It might also be worth trying a semi-synthetic oil.
Remember that the clutch is a wet clutch so is immersed in oil. Going to a fully synthetic oil or an oil with anti-friction additives (such as many car oils) may cause clutch and starter motor slip.
Oils such as Repsol Semi -Synthetic 10W40 state that they are :-
'Suitable for combined engine/transmission/clutch lubrication of the latest generation or 4-stroke motorcycles, ensuring excellant performance".
It even has an illustration of a Diversion on the front of the 4 litre container ;-)
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Q/
My XJ900S has an irritating sticky clutch. That is, whenever it has been stood for a good few hours or more the clutch doesn't disengage properly causing the bike to lurch forward when putting it into gear for the first time. After that first time it remains absolutely fine until it has been stood again. I have found that, after it has been stood, holding the clutch in and reving to about 4000rpm several times before engaging gear sorts it out. Does this sound familiar to anyone else? (BTW the local shop dosn't have any ideas). I can live with it but I wondered whether it was a peculiarity of the bike or a problem with my particular clutch.
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A/
The clutch is made up of several plates, which sit in a slotted basket. They alternate between driven plates and driving plates (ie the driving plate connects through to the engine via the basket, and the driven plates connect through the gearbox via the idler shaft, to the wheels). The driven plate will have a splined hole in the centre to lock onto the splined idler shaft, but no tangs on the outer circumference. The driving plate has tangs on the outer circumference to lock into the slots in the basket, but a smooth hole in the centre. It is the grip between the plates, pushed together by the clutch springs, which takes the drive through to the gearbox to the wheels.
If left for a while the oil is squeezed out from between the plates by the clutch springs, and this gives a vacuum effect between the plates.
When the engine is started with the clutch out, in neutral, all the plates turn as a unit. The drive through into the gearbox is turning an idler shaft only, so no drive through to the wheels.
(By starting the engine with the clutch in, the idler shaft won't turn, and this makes for less strain on the starter. HOWEVER, this is only beneficial if the oil is very cold (and therefore thick), and if the plates have separated and have oil between them. It works best for dry clutches, as in cars.)
Once the engine is running,the oil is getting stirred up. By exercising the clutch, or holding it in for a while, you are allowing oil to get between the plates and break the stiction.
The lurch happens because as you put the bike in gear you are locking the idler shaft into a gear (first gear), which goes through to the wheels. Because the plates are stuck together it's as if you have no clutch at all, and the drive goes straight through to the wheels.
Because most bikes with wet clutches are built in much the same way, they all tend to have the same problem. The only damage that occurs is the tangs get worn where they bang up against the basket slots. This also happens everytime you change gear, up or down, and is worse if you do not change gear smoothly.
Hope this all helps.
RogerD
