Has it been tipped on it's side? If so, the muffler will be full of oil - just let it burn off (and check the oil level since some of it will be in the muffler). This may take several minutes.
Is the oil level correct? Too much will smoke.
If niether of these applies, then the only answer is an engine strip, or replacement.
phil_saunders@bigfoot.com
Phil Saunders, July 2008