As a long shot.... May just be down to a shortage of fuel in the carb float bowl having evaporated over the time spent standing, that is where an electric pump can help if prior to cranking one listens for the ticking of the pump to stop which informs one that the carb float bowl has been replenished.. Old style mechanical fuel pumps had a lever which could be used to manually pump the fuel prior to cranking in order to achieve the same ends... I guess a modern way round a similar problem could be a short squirt of easy start to initially fire things up...? Though be careful spraying that stuff around as it seems engines may get somewhat hooked on it... or you can set fire to things...!!!
Also modern fuels are quite a bit different and can perhaps loose some degree of their combustibility if left for long periods of time..?
Just thinking in type. Hopefully someone more knowledgeable comes along in time..
Good luck in finding a solution to your issue x 2.. (-:
