A distinctive feature of the 500/550 engine is the polished, rounded, pretty, but purely decorative covers at the left and right ends of the cylinder head. Though held in place by just one countersunk ("oval") Phillips screw, the part requires the rather intricate bracket behind it for support. The bracket in turn is bolted to the rockerbox or cam cover by means of one of the cam cover bolts, at each end of the head.

While I was employed at corporate Honda at the beginning of the 1980s, the service division in which I worked borrowed some office space located above the Western Regional parts warehouse. Upstairs. Huge picture windows allowed us to look down onto the warehouse floor below. I was able to convince someone in the Parts division to make a physical check of a part number discrepancy, and they did so, confirming my findings.

At that time, Honda still issued paper partsbooks for use by US dealers. And owning a CB500 at the time I discovered that Honda had unfortunately transposed the part numbers of two washers, one steel and one aluminum. These were the washers on either side of the bracket that the decorative cam end cap bolted to. The aluminum washer is supposed to be below the bracket and against the rockerbox, the steel washer should be above the bracket and under the head of the bolt. But in the partsbook, the numbers were swapped. Although seemingly minor, this could result in an oil leak at this bolt. This issue is what I was able to confirm that day.

Electronic parts diagrams may have this corrected. I have not checked. But the bottom line is, the aluminum washer goes at the bottom of the bolt, the steel one at the top of the bolt. Be sure to get them right.

On a related note, you will observe that not all of the rockerbox bolts and screws have washers on them. Only those fasteners that are inside the sealing area of the rockerbox o-ring have washers. Be sure they go onto the correct fasteners.