When I put it away last year it was behaving itself, second run of 2018 and the mis fire returns.
It seems to be directly linked to throttle opening, and when the engine is under a heavy load - going up hill is a good example.
I have visions of a small pin prick in the carb diaphragm, or a small air leak on the intake side perhaps.
As I was bimbling along today, I thought to myself yet again it is fuel related and wondered if perhaps there was a problem with fuel flow to the carb.
Plenty in the tank so I turned it onto reserve - what a huge difference, no matter how hard I tried I could not get it to mis fire, and it felt like it was goig better than ever before.
So, is there a problem with the fuel tap - vacuum operated or has it once again lulled me into a false sense of security?