the worry is if there is rust on the cylinder walls.... I doubt there is but their could be.... and the cylinders are probably still full of gas ( it takes a while for it to seep past the rings to get into the bottom end.)
but just play it safe and lube up the cylinders with either alot of WD-40 or just plane o'l oil.... take the exhaust pipes off first though so you don't get a bunch of oil in them.... LOL
I expect it will turn through fairly easy which is a good thing... but if it doesn't make sure it is in neutral first and then rock the wrench back and forth to try and brake the rings loose of the cylinder wall ( they rust to the cylinder wall and get stuck ) usually just a few tugs back and forth will brake the stuck rings loose from the wall.... and you'll notice a crunchy hard spot when turning the crank 360 deg. as they come back to that same rusty spot.... that will go away
without having to tear it down and honing the cylinders.... but if you have to tear it completely down anyway, just hone the cylinders and replace the rings
as part of the rebuild.
....
I remember making a major blunder in my youth, I was trying to set points on a Zundapp 200cc but when I took off the cover the crank wouldn't turn very far and then sprung back ....so I could not figure it out so I took off the clutch cover and tried to turn it again and saw that the transmition was engaged !!!! I felt like an Idiot ! put it in neutral and it turned real easy !
one of those lessons that you never forget !
....
Bob......