Normal is between 25 and 40 ft-lbs, depending on how the loads will be, and which bushings are installed. With the original straight OEM phenolic bushings found in the 750K1-K6 and CB500/550K1/2 and CB350F the 25 ft-lbs is enough. The later flanged phenolic bushings (CB750F and K7/8, CB350F2, CB400F, CB650K) should be 25 ft-lbs, but often got tightened to 40 ft-lbs because there was confusion when the MIMs-metal injetcion-molded bearings got subbed in for the phenolic parts in a change by Honda's parts techs in the 1990s. This was too much: it caused many cracked-off phenolic flanges on those later flanged phenolic bushings.
If you install proper bronze bushings and matching collar (i.e., less than 0.0010" clearance between the two) then the 25 ft-lb number is OK. If you use bronze bushings that have the flange on them, you will have to first file the flanges flatter so that the collar can stick out past the bushing flanges in most cases (I've only seen 1 set of flanged bushings in the last 20 years that had a thin enough flange from its maker). The collar must be at least 0.002"/0.05mm longer than the ends of those INSTALLED flanges, and then you can tighten as much as 40 ft-lbs and the collar won't compress too far.
