Wet clutch Q & A
Q: I know we have a wet clutch. And I know that means the clutch plates are in with the oil. What I don't understand is why. Why have a wet clutch at all?
A1: The reason is because it is easier and cheaper to have them wet rather than dry, due to where they are located. They live in the primary gear case, along with a lot of oil.
A2: The reason for using a wet clutch is to help lubricate and cool the clutch, thereby making it last longer. Automatic transmissions use multi-plate wet clutches just like the ones in our bikes for the same reasons, longevity.
Q: Why is the bike harder to push in gear with the clutch pulled in than when the bike is in neutral?
A: The oil is a viscous fluid that acts to "stick" the clutch's friction plates to its steel plates. This creates the excess drag you feel when you try to push the bike in gear with the clutch disengaged. There is oil between the plates and the plates stick to each other a little bit. Totally nothing for an engine, but humans can feel it. Once it is warmed up it doesn't drag much.