If I was to change the oil as you suggest, should I need to disassemble the clutch and soak the plates in oil before reassembly, or is that only for a new, dry clutch?The simple answer about M__ is the friction index. Low value = low friction. High value = high friction.
DFI is Dynamic Friction Index, SFI is Static Friction Index and STI is Stop Time Index.
MB is lowest friction oils, used in dry-clutch bikes like Ducatis and some BMW's. The clutch is not swimming in it.
MA is for wet clutch, but tolerances on index are high see sample 4-9 above.
MA1 and MA2 both qualify as MA oils, but have tighter specifications.
MA2 has the highest friction. This is the only oil to use!
See table above.
Read on the label when shopping. Should say: Fully synthetic. JASO MA2. API:SM. Brand or price is not relevant!