Wingman,
There you go, put that Saito on a 46 size UCD. Missleman might have a point there, check the valves, maybe the old Saito is ready for a rebuild.

I think I remember reading they were a heavy old pig. The ST 61 should be much better than the 80.

If I had the cash I would go with a YS 110 on the UCD. My UCD would hover at about 5/8th throttle with the 91.