Make sure that you have fresh oil in the crankcase. Remove the spark plugs. Put the tranny in neutral. Using either a torque wrench or breaker bar and a socket that fits on the large nut of the lower crank pulley, see if you can rotate the crank by hand. If you can turn the motor over by hand a full 720 degrees (twice) without any binding or funny noises coming from the valves or crank, then it is probably safe to try using the starter. Install the spark plugs and try it with the starter.