It's been sitting for 2 years...
First thing to do is a full service, including a new set of spark plugs and a water pump impeller. I would also pull the carbs, fuel pump and fuel lines and give them a good clean. Replace the pump diaphragms and the fuel filters.
While you're doing the service, check that everything that should move, does. Many pivot points dry out and get sticky, throw some grease around while you're at it.
What year (or serial number) is the engine? I can give you a link to the service manual with that information....
Chris............