My 6spd gearbox works very well, but I do miss shifts on occasion. My attempt at a remedy is threefold.
1) Because the 6spd CB360 shift drum cam has an extra detent roller slot (6 compared to 5) there isn't need for quite as much "travel" of the 550 shifter shaft. I machined a bushing to fit over the end of the return spring pin which will reduce both shifter shaft travel & drum rotation. I believe with slight over rotation the detent roller didn't always center in the cam slot and would result in a false neutral.
2) The cam plate seems to be a stamped piece and as a result isn't a smooth surface for the detent roller. Hondas rollers also wear with time and can become quite sloppy. I picked the best of the ones I had but wasn't really happy. The 550 main detent roller is only 2.3mm wide but the cam is fully 3mm wide. I decided to try 3mm wide mini ball bearing rollers so the rolling surfaces matched widths.
The larger CB550 roller's OD is more than 1mm larger than the CB360 counterpart, potentially not locating the drum into position as well as should be. So now the bearing roller OD is smaller plus it and the cam rolling surfaces were smoothed and polished as well. Both bearings are identical, but just pressed on a machined piece to enlarge one.
3) I felt a slightly stiffer detent bracket spring might help as well. I haven't yet tested the spring rate difference. The neutral roller spring is ok.
This picture shows some of the mods, the relocation of the shift fork shaft, (not centered in the old case hole) and the modified shifter shaft. It sure doesn't look like the intricate Honda manufacturing we're used to, but it works, and hopefully now will work even better.
