The stock gearing on the 550 was good when the rear tire was the stock 3.75x18 size. The more commonly fitted 110/90x18 today is taller, and the often-accidentally fitted 120/90x18 makes the bike WAY overgeared and real doggy, not to mention it is 35% heavier than the OEM tire.
The difference in sprocket life between steel and aluminum, with equal amounts of lube, is dramatic. The steel ones can easily exceed 30000 mile life on a 500/550 if flipped every 5000 miles and lubed every 1000 miles, and cleaned regularly. The aluminum rears will yield less than half that many miles, typically, and the aluminum fronts will struggle to make 5000 miles before the splines wear quite a bit, lube or not.
Aluminum got popular when they were cheaper than steel: they weigh a little less (about 60% of the steel ones) and are popular on race bikes for that reason. On road bikes that tour, in particular, the aluminum powder grindings will fill in the gap between the chain's rollers and sideplates and will jam the rollers: on O-ring chains the powder will slowly eat the O-rings. Frequent washing can mitigate this issue: it's just a little more maintenance.
When the chain alternates between tight and loose on the sprockets, it is more often the chain being irregularly worn than the sprockets. If an oval sprocket does this, the chain will tighten-loosen twice for one revolution of the rear wheel: if it takes more than that much wheel turn to tighten-loosen, then the chain is uneven.
Check the Thoughts of Hondaman FAQ
for more info on gearing the 500/550 bikes.
