Hey Doc! I finished the restore on the 650 yesterday and ran the engine under a mower load. It worked great! NOW -- with a load on the engine it runs at a very stable 1500 to 1600rpm at full throttle (throttle plate/disk against the stops). I think these Wisconsin S8D's have a max rpm of 2900. SO -- my question is what governor linkage parts do I need to push the rpm's up to operational speeds? Yes! This is the NOS engine I bought and YES! The engine gov. linkage seemed to be set up for a fixed speed. It mows just fine at those rpm's but does have a tendency to load up in tall grass.
See link below for the variable governor assembly: