My KV-2 turret now rotates. I separated the upper hull from the lower hull, cranked up the tank and still "no joy" on the rotation. It rotates freely without the motor assembly attached.
I balanced the turret with plane weights on the back of the turret and glued the clutch.
Had the same problem with the barrel not elevating. I added a couple of weights on the back of the recoil motor unit, glued the clutch and loosened the spring.
Either I received a couple of bad clutch assemblies, but I think the clutch needs some re-engineering. It seems weak for the heavy turrets and barrels.