Many 500/550 riders are resigned to always needing to increase the engine idle during warmup and subsequently lowering it again early in the ride. As a career mechanic I have never found this acceptable and neither of my CB500s have been treated this way. Professional mechanics view raising and lowering the idle as indicating a problem in the engine. And it is observable that few of these bikes are properly tuned, at the very least, and this is why idle fiddling is necessary.

Of course, raising and lowering the idle may be mandatory if the bike is being ridden in very cold ambient conditions. But this is mostly if not completely overcome by using the appropriate grade of engine oil. A heavier than normal oil will affect warmup even in temperate climates. Simply put, outside of these exceptional cases, you should not have to play with your idle. It's considered gauche in technically knowledgeable vintage Honda circles.

It is noteworthy that speaking specifically of those SOHC models having the original, first-generation series carburetors, only the CB350F/400F received a fast idle mechanism as part of its choke system. Many a first-gen CB500/550 and CB750 rider has wondered about that. Of course, the last year or two of the 550 and then all the 650s and the last couple 750 models eventually got different carburetors with fast idle capability. But those are different carburetors and to most including myself not as desireable as the original carbs.

Some folks are also retrofitting the 650 primary chain tensioner to their half-litre Hondas. There is of course a good reason to fit that part, and it's not hard either. But the goal should be reducing driveline snatch, which a 500/550 is particularly prone to, not to reduce clatter at idle. Properly tune your engine instead. As to a CB500/550 fast idle solution, that's not difficult to do. There are a couple ways, including fitting all the choke linkage from the 350F/400F, which while expensive is the most elegant approach.