Your Yamaha 440ss only runs with choke on?
Clean your carburetor's main circuit. Your carburetor contains
two "circuits." One is the main circuit, and it puts gas into the
engine with the "choke" off. The other is the enrichment circuit,
which puts more gas into the engine because a cold engine needs a
richer fuel/air mixture than a warm one. If your engine only runs
with the choke on, that means no gas is coming in via the main
circuit, which means it's clogged. Clean that out good and it
should fix the problem.