ding ding ding!!! I had a spare rotor lying around and decided to throw it in and see what happened. When I removed the cap I could see the tip of it looked spent. I then took 30 minutes trying to remove the old rotor , and had to go at it with a grinder and chisel! even with it half broken off the shaft it didn’t want to come off
Eventually got it off and put new rotor on. BAM fired right up. However now have a heavy knocking. So might have damaged a wire. I’ll get the tune up completed when the parts arrive in the next few days and replace everything