Eh, the smoke could be anything really, water, burning oil, etc... But yes 270 really should be the max. Can you start it when at running temp ok? Thats when you can tell it's going out. Other way to tell is if it has lost it's power, compaired to when you bought it.

Try and richen it up at LEAST an 1/8th of a turn and see where it goes from there, won't hurt to go 1/4 of a turn.