possibly water in the carb bowls or tank. check that first. then checkout carbs for repair, maybe dryrotted seals and orings from sitting dry.

take carbs of and clean thoroughly with a good carb cleaner.
then the main body sit in for a few hours or even over night then blough through all the orifices with airline.
now before you think you have done it, you need to pop out the small freeze plugs on each carb as they hold crud in their tiny little orifices under there too.
you might of run the carbs dry, but did you undo the drain plugs on each carb before you tilted it up ?
what about the fuel sitting in the bottom of the plastic fuel manifold.
plus what about fuel in the main fuel lines ?
there will be fuel in there still that is trapped and will go bad and turn to varnish.
for the price of nice new fuel lines I would also change those.
go to auto store with old pipes and match for size its real cheap stuff.
also the old fuel in the tank will have gone real bad and will be sitting in the tank like a gung/varnish and will creep back into carbs and cause problems.
whatever is in there dump it..8 weeks and fuel is bad,very bad..4 months its not even petrol anymore.

seafoam is a good preventative, but wont clean what is already bad !!!!


phill