The 1972 and 1973 until mid-year are all but identical. The ones after that came in 2 ever-so-slightly different versions, with minor differences in the suspension being about the only way to tell them apart. All of the pieces from all of the years interchange.
Could you elaborate on these differences. What exactly were the differences in the suspension?
There are 2 different dampers ring sets in the front forks, early to late. One has more holes than the other, but at the moment I don't remember which is which, there. I suspect the later ones have less holes, though.
The swingarm pivot on the early ones had 2 grease zerks on the ends of the big bolt. Before 1973, this became one zerk on one side of the bolt. In early 1974, the zerk moved to the bottom center of the swingarm itself (like the CB400F). The phenolic bushings in the early ones came straight from the CB500, with felt washers and end caps like the Big Fours had, and the holes in the swingarm are bored 2.2" deep to accept the longer bushings, despite the fact that the collar has only 1.6" of bearing area. In the "middle" version the bushings changed to flanged ones that were 1.775" deep, with no seals. In the final version, they were shortened to 1.675" long total length over the flange, and the arm was not bored so deeply, accepting only 1.7" deep bushings. The latter 2 systems wear as quickly as the one in the CB400F, which yields about 10k miles of decent handling, followed by wobbly feelings.
I make whole bronze retrofit rebuilds for them, with new, hardened collars, all custom fitted. It's not a kit: I have to have the arm to do it. Honda's parts DON'T fit it today: there is some sort of error in their parts interchange system, and incorrect bushings are being sent out to folks when they buy the parts. I get a lot of those...
The tires also changed on the last year, as did the material in the rear brake shoes. The earlier ones often squeaked. The "new" rear shoes have little grooves cut across them, too, and the material is more smooth and stiff. It worked better.
The 3 things that really boost the suspension performance on the Baby Four:
1. Roller steering head bearings, a must.
2. Good swingarm bushings and collar.
3. Air forks, because the front springs sagged very quickly and travel ended up at 2.5" with loss of trail.
And, rear shocks with real damping improves the corners, too. The OEM ones lost all damping in about 5000 miles or 2 years, whichever came first...
