Nigel,
Is the kickstart shaft sloppy through the bushing in the outer cover? Is the outer bushing still a tight fit in the cover. I am emabarrased to say that I let mine go with the outer bushing working its way toward the kickstart lever. Eventually, the quadrant spindle broke at the inner bushing. Even with it broken it would engage the ratcheting pinion and let me start the bike, but it also jammed up, sort of like you are saying. I didn't realize this is what was happening until the outer cover broke away around the bushing. These comments could be titled, "What I Did Last Summer", or, "How I Learned About A10's the Hard Way", or "A10's for Dumberers, an Autobiography".
Richard L.