Just had the same issues with mine.

The main problem was all the green sludge in the carbs, whip off he float bowls remove your main jet its holder and the slow jets.

Soke them in full strength coke, yes coke and leave for 24hrs, the brass comes up like new, but I had to soke the slow jets for another day as they were full of shite and were very stubbon.

Give them a rinse, blow through for good measuer and try again, also clean the float's plungers they gum up to, ohh dont forget get to give your needles a whipe a they can attract the green stuff to.

And put a fresh battery in for good measure, and check how dry the air filter is.
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