Weird, Tall Paul.
Are you sure the Bell-Hiller mixers haven't flipped over, they can do this if you have the bell mixer arm pushrods unhooked from the swashplate, and it is possible to re-snap them back in with the mixers upside down, and it will look right (mirror-image) but the thing won't fly for beans like that. If you've unhooked the one that doesn't fly from the swashplate, you can't even compare to tell if that was the problem because the links will be loose now.
I'd try putting the non-flyer back on, making sure the Bell-Hiller mixers get flipped the right way, and try it again. If it still doesn't work, we'll have to check something else.

Ahh, Palmdale, Plant 42, the wind, the sun, the wonderful airplanes, the wind, the winnnddd...