what is happened when you turned it? did it get harder and harder to turn, or did it go clunk like the piston is hitting something?Pulled the cover and did a motor seize test: Motor will turn about 20 degrees in either direction but will not complete a full revolution.
When the spark plugs are in the motor will build compression just turning it by hand. The wrench will feel like you are loading up a spring (you are, an air spring...)
If that is the case you can either take the plugs out and try again, it should feel the same all the way around
or if you are sure its just the compression you can put a little more force on the wrench and push it past the compression stroke.
And again, only turn it clockwise. There is a timing chain on both cam shafts with a tensioner. The chain pulls the cams around in the clockwise direction, and the tensioner is past the cams. If you spin the chain CCW all the slack pulls out of the tensioner and the timing on the cams (valves) is off, and there will be slack in the chains.
You can back it off a little bit CCW, but not far.
If the crank feels like its hitting a hard stop when you turn it (and you have the bike in neutral - bike rolls freely while not pulling the clutch) then something is mechanically broken in there.