If it sat all that time with fuel in it, then it needs a dose of Sea Foam fuel additive. This engine had a 24 month warranty and it just passed by on the 13th!!!!
I recommend 30 Kawi engine oil, give it a dose of Sea Foam in the fuel tank, if it is surging at high RPM then it probably has a fuel problem in the carb from sitting. Run it and get back to us!!
My equipment is stored in my cargo trailer and if I go thru a slow period of lawn mowing of as short as three weeks, the fuel in the carbs can start to turn sour and need a dose of Sea Foam. I also use Star Brite fuel additive and a carbon softening additive when mixing fuel for my 2 stroke equipment.
Mad Mackie in CT