take the plug out and the side chain cover off and see if you can crank the motor over using a wrench on the clutch, go gently, the motor should spin easily, if this doesn't do it then the starter mechanism n=may be jammed so remove and check.
If no fault found then it is oil down the spark plug hole and wind over with a wrench on the clutch time - I wouldn't think the engine would seize through standing but the above should help just don't use excesive force.
Steve
March 2009