How do I remove the clutch backplate on my Suffolk Punch Mower?!!!!!?

Hi, I have removed my engine from my old Suffolk Punch. I would like to get the valves out and re-seat them. I undid the 6 or 8 bolts holding the crank case together, stupidly not draining the oil first(!) but need to get the clutch backplate off, I think, to remove the case cover and get to the guts. I have found this impossible. Does anyone out there know how to do it, or is there another way from the other side where the big fan thing is held on with a bolt (which I removed and nothing moved?)?. HELP!!!!