I'll "me too" with Dennis' comments on break in. I wish OS would update their instructions. Btw, the best break in info I've seen came from the Jett website. Dubb Jett is a guy who KNOWS engines, so I trust his word on such things.

2 cycle is the engine firing on every revolution, in 4 cycle, the cylinder only fires on every other revolution of the crankshaft. Basically you get 4-cycling on a 2 stroke engine by richening it up. You can really hear the change, starting rich, from a 4 stroke, to a transition range where it's firing on most revolutions but still missing on some, to a "clean" 2 cycle. Once you hear it, you'll know it.