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.