Had a 1200 v low mileage that ran like a pig. All it needed was new plugs, the ones in it were barely touched but had got wet. Odd. Very sensitive to plugs.
However flooding carb would make the plug wet.
Take carbs out, connect to a remote tank, let them fill up. If fuel starts pissing out its needle floats sticking or shagged (they go in the end). Floats should be fine because they don't adjust themselves.
OEM is a good way to not have problems. Anything else good luck.