I just received a cub cadet 73 from my grandfather that is bogging the engine down when I engage the blades. All the pulleys move freely and the belt can be moved by hand at the front of the engine. I had the deck off and checked that the pulleys were not binding and that the blades were free. The compression is around 70 lbs but I dont know what it should be on this engine. It is a model K161 and serial # 1003658. Any thoughts on where to look next will sure be appreciated. Thanks, Chuck