if you have to pull the choke, your engine is not getting enough fuel.
I've noticed carb problems on these 550s tend to happen quickly.
the first thing i would do is remove the fuel line from the carburetor and make sure the pump pumps when you crank it over, it'll shoot out in bursts.
if that looks good, i would remove the carburetor, two 10mm nuts, 10mm bowl screw, and spray out the main jet and all the air holes in the venturi with carburetor cleaner
I had recurring problems with my carb since the fuel tank is a little rusty, getting rusty looking sediment build up in the bowl. i installed two filters, one before the pump and one after the pump and i have had no more issues.