Just normal 10w40 motorcycle oil. Like maybe Mobil or something? It's definitely designed for wet clutches and is not car oil.
1200s do have hydraulic clutches, 1000s and 1100s do not. :wink2:Billy: I acquired and restored an 85 Aspencade last year and have the same issue. Hammer down 3rd and 4 Th. gears heavy acceleration the clutch slips. With a wink to other Insistent posts here- Mine is certainly hydraulic.
What's the JASO rating?
Personally, I don't think it is oil causing your slippage. You will probably want to decide if you can get the swing arm off, or if you will need to pull the motor.
Either way, the clutch is going to have to come out. The damper plate is no longer available new, so you'll need to figure out how to rebuild yours.