K161 ??
 

I tore down a 161 off my sons model 72 and while re-assembling, following the manual, when I torque down the governor bushing nut, it cinches the cross shaft and does not allow it to rotate, also per the manual it calls for a "plain washer", no gots, there was not one on there when I dis-assembled the engine so I'm thinking this may be the issue, does anyone have a nice clear picture of the parts breakdown for this. or maybe a clue as to whats happening??

The 72 should have had a K161-30564D engine.

Attached is the Governor image of that engine.

This is the complete setup, no washer is used.

What is/are the difference between the K161 on a 71, or a 72 and a k161 from an Original?
My son has an original that I have to rebuild and a 71 that I have not looked at to assess the condition of,
as of yet.

Nothing. The engines are the same. The setup on the tractor is different. The O belt drives the driveshaft, the others are direct drive. The O didn't necessarily have a front PTO, the others can/do.