Took the engine apart on my '80 CBX to rebuild and paint, something to do while I'm awaiting surgery since had time on my hands. Been slowly re-assembling and yesterday rebuilt the clutch to install. When I went to install the clutch I turned the oil pump drive gear and after 1/2 a turn it stopped. Removed the drive and tried a flat screwdriver, with which pump turned fine. Tried drive gear again and pump stopped after about 1/2 a turn in either direction. Since pump turned fine when out and with screwdriver, I'm thinking it must be miss-aligned slightly causing the drive to bind in the pump slot. Turned pump with screwdriver, looking for any wobble and seen none. Tried getting at the mount bolts from sump to loosen but couldn't do it. So took about 1/16" off the pump drive shaft tab faces and now pump turns fine with the drive gear.
When I installed the pump, dowels were in place and the three bolts torqued properly. Just never thought the install the drive gear and give it a spin before putting the halves together. Sharing this as a heads up to others.