Originally Posted by miamijim

The 721a was originaly spec'd with a Shimano Mountain LX front derailleur and a Biopace crankset. typical FD setup call for it to mounted about a nickles width above the front chainring. With Biopace rings you simply align the crankarms with the seat tube, lower the FD so its about the thivkness of a nickle above the ring and tighten it up.

That can not be done of the 721a because the inner FD cage will heavily rub on the middle Biopace ring. to fix the issue you have 3 options:

1. Raise the FD high enough so it doesnt rub the middle ring. This isnt very feasable because it needs to be raised so high that shifting is compromised and so high that the chain will drag on the tail of the RD
2. Ditch the Biopace rings
3. Ditch the FD

My recommendation is to ditch the outer and middle Biopace rings and then lower the FD to its proper height.