I might mention that the CB500, when it first arrived, had progressive springs that were too soft. When a typical rider (150 lbs was considered 'typical' then) sat on the bike the forks sank over 2", leaving little travel for suspension use. Two-up riding left about 1" of fork travel (and 1" of rear shock travel, too). Somewhere in the timeline Honda made a little stronger springs in the front, but the 'hot setup' in the CB500 Four back then was to install straight-wound springs supplied then by Forking by Franks, accidentally from a dirt bike, that fit. We also cranked up the rear shock adjusters to their top positions. Riders all noticed that difference, and most liked it. The 500/550 with Vetter fairings got air fork caps when my shop installed the fairing. They needed it!