Right, dropped and emptied the fuel tank.
Also removed the carb for a refresh. During the process, I because less than confident of one of my floats. So it's all back together, but I've decided to wait until I replace the float during the week before I fire it up.

The only times I have ever had this problem is if I pulled the distributor out and "put it back in exactly the same position as it was before". Yea right. I always had the timing retarded too far. Usually bump it up and it will be fine. Never had to drain the tank of fuel and put fresh in it. Yes it does burn differently when old, but I never had a problem with it.