MM
I had a hard time with mine so I removed the plug and checked it.  It seemed dry, and only smelled faintly of gas.  I resorted to an old RC trick of squirting about a 1/8 teaspoon of gas into the cylinder, reinstalled the plug and made sure the SP wire was connected correctly.  After this I left the choke open (and air cleaner off) and rolled down the road.  When I engaged the clutch I got a couple of  sputters.  This hinted at a fuel problem. 
When I checked out the carb I found that the (throttle) piston wasn't moving as I moved the throttle.   The little lead ball had come off the end of the cable!  I guess I should have checked this before squirting the gas in, but I didn't think that could happen.  
After replacing the ball the engine started...  Actually, I have a small hill in front of my house and I used up about a 100 feet of it (length, not elevation) to get the engine to kick over enough to run.
Good luck with yours.