Worn out primary Chains
The primary chain is not my concern. As a matter of fact I'm on my way proving how long it can last (now: 135.000 kms). Haven't seen or heard of an oil gally that was
actually cut open by it. The morse chain itself is oversized and well capable of handling much more HP than the 50hp the CB550 delivers. No, my concern is the camchain tensioner. It's by far the weakest point in the engine design (mind you, back then this was the case for almost every motorcycle). Ón mine the tensioner was replaced at around 45.000 km and at around 80.000 km and if I'm not mistaken I can now order number 3. The CB500/550 bottom end is practically undestructible.
Carbs: the less you touch them, the better. Cleaning is OK and sometimes inevitable but tampering with floattangs and raising/lowering of jetneedles - I know that manuals like Clymer are happy to fill pages with it - but I'd stay away from it. Bear in mind that we all, looking at these impressive exploded views, sooner or later, fall victim to some degree of delusion of reference. For an experiment I raised my needles but I think of returning them to the 3rd and middle position, maybe with a thin shim. If your floatlevel is not as it should, try to elimenate other causes like non original fuellines, sticky floatneedles and obstructed vents. A sticky floatneedle is hard to detect by the clear tube method, but you
will notice it when you check the floatlevels the way Honda described. Adjusting the tangs IMO is only needed if the PO was a reader of this forum.
Use genuine Honda parts and your Honda will
remain to be a true Honda, a very reliable and tough bike.
All in all I liked the first CB550K (small blinkers and taillight) best. Only change the handlebar for the euro version and it's a perfect allrounder. However, I don't know if that first model had the improved swingarm bearings yet. K3 and F2 I dislike most. Good things were changed (wiring inside the handlebars, frontfork protectors abandoned) for inferior (PD carbs, horrible oversized blinkers and taillights) and all them tubes all over the bike (K3-4), yecch!