I noticed a small leak under the "dynamo" cover on my 1977 CB750F. I pulled the cover off to address a charging problem and noticed a coating of oil throughout the compartment and a small pool of oil at the bottom of the cover. The oil could be leaking past a seal in back of the rotor...which I don't have a removal tool for yet.
Any ideas where this oil could be coming from?
The 750 naturally carries oil in the alternator. No problem there. If memory serves there is no crank seal on that side, I'll check a microfiche. PS: I checked, don't see a crank seal on the alternator side.
If by leak you mean its leaking on the floor, that's likely just the gasket between the dyno cover and the crankcase. Fairly common.
Put the bike on its centerstand. Prop a sliver of wood under the foorpedal of the centerstand to give it a bias lean away from you so oil drains back into the crankcase from the alternator. Remove the dyno cover and replace the gasket.
PS I just reread your post and see you already have the cover off. All's well to reinstall. Be sure that gasket is in good shape as it has a job to do.