what type of ski do you have first?
The PTO is different for 97 and newer xp's and hx's...
The best way I have found is set the motor on the ground and take some cotton rope. put about 10 - 12 inches of roap down the spark plug hole careful not to let it come out the exhaust or intake ports.
Slowly by hand turn the PTO till the rope is compressed in the cylinder and is evenly distributing pressure on the piston.
next, get a buddy, a pipe wrench, and a long braker bar (about 3-4 feet long.)
Have your buddy hold the motor in place and attatch the pipewrench and breaker bar extension about 4 inches off the ground.
now when your buddy is ready, stomp on the breaker bar to shock the pto off....
It will spin freely from there.