iceman, if it is not a hydraulic system, then yes it can be a cable much like the clutch cable, which pulls a lever on a brake drum centered on the wheel hub...

If you happen to have a hydraulic system, and the bolt you mentioned has pinched the brake line, it can possibly still have enough open area to allow fluid to pass by and operate the caliper piston(s) well enough. If you think it is compressed too much where the bolt pinched the line, and it isn't moving the piston in the caliper adequately, I'd replace the brake line...

EDITED: Damn, sometimes I gotta laff when I get in my 'instructor' mode! Re-read your post, and I understand what you were asking better now!

 

i have worked on hundreds/thousands of them old bikes, probaly isnt the caliper, most of the time it is the mastercylinder,if you can clean it up good, there is rebuild kits for them, your best bet is a new universal mastercylinder from ebay. if you pull the lever and then the bike wont roll, then it is the caliper... all old jap bikes front brakes lock up after sitting a while

 

Get yourself a Clymer manual for this model, study it and you'll have no trouble learning how to fix it.

It could be as simple as bleeding the brake .


I had a 75 CB750F ( 4 into 1 pipe model) back in the day , went like hell after I put a supercharger on it.

The F model had front and rear disc, shorter rake and shorter gearing , respectable stock in its day.

The 76 had 3 versions an automatic , 4 pipe and the F1 four into 1 pipe style

Its nice to hear about one still on the road.

 

thanks for all the responses. i like the idea of bleeding the line first, makes total sense. if that doesnt help the situation ill probably tinker with the caliper, but bring it to the shop after that. i suspect that it is as some of you described: some sort of blockage or sludge somewhere in the line. (hoping, at least.)

clymer manual was ordered a few days ago, will have it soon. thats the first thing i buy for all my bikes.

reason for purchase: recently i bobbed out a suzuki savage and really enjoyed the project, enough to want to do another bike. at some point decided i wanted a cafe racer, but would rather do it myself than buy one already done, figured why not do it with a classic piece of motorcycle history.

the bike is in pretty good condition. everything works, kick starts fine, no rust on the frame, electrics are good, no leaks from the engine. theres some (ok a lot) of rust in the tank, but ill be replacing that anyway. only other issue is the front brake. oh, and the previous owner swapped the fork tubes for +8s, so the front end is raised quite a bit; i plan on going back to stock if i can find the parts. should be a fun project.