Just bought a beautiful 1976 750 F Super sport that is completely original down to the paint and exhaust. Bike runs great but clutch refuses to release, no matter what I try. I have pushed to get rolling and then started the bike, tried on and off the throttle hard with clutch lever pulled and going to a higher gear and really pulling down on the engine, nothing has worked. The previous owner tells me that it was fine last fall. I find it hard to believe that in one winter it has frozen up this badly! Suggestions, not a great mechanic.