Hi Keith, I just wondered if you had checked whether or not the plug gets wetted with fuel as it should do if the fuel is getting through but it’s not firing up?
If the plug is dry, try putting a few mls of petrol down the plug hole, refit the plug and try kicking it again.
If it fires into life just for a few seconds then it proves you have a spark and at more or less the right timing and shows that it’s likely to be a carb problem.
If the plug is really wet, is the carb flooding? If you have had the carb to bits to clean it, have you lost/misplaced the little rubber disk off the end of the choke plunger so fuel runs in all the time?
I would be interested to know the answer as my TS250/1 motor is also in bits at the moment for a new big-end!!