I have a Clymers manual, which I've found to be very helpful. I've also probably got the same downloaded PDF that ccRider has. Somebody else posted a link to it here a few months back. It's on another forum, and I think you might need to register to download it. But it's worth having as a reference. Even though the scan quality leaves a lot to be desired, the exploded diagrams are VERY handy to have:
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=5It also has more specs and numbers than you'll find in the clymer's or haynes manual. But don't just rely on the PDF. Get an aftermarket manual too. What I've found is that they'll have useful tips in them that aren't in the factory service manual, because FSMs are reluctant to point out faults and weak points on their own bikes. For instance, the FSM doesn't stress the importance of not over-torqueing the oil filter bolt. But if you put much more than 23 ft/lbs on that bolt, you've got a great chance of breaking it.