Three things. First, you can see from this reproduction of the parts book how unusual the CB500/550 Four cam chain arrangement is. Specifically the cam chain guide near the front of the engine. It is not like any other Honda SOHC Four. The difference is in the cam chain guide (1), which faces outward instead of inward as it does on most other Hondas, and thus installs inside the cam chain run instead of outside it.

Second, the cam chain wears fairly quickly. A worn cam chain delays the cam's timing relative to the crankshaft, reducing engine power. Replacement cam chains are available, including Honda's own, the preferred one, and are easily installed without removing the engine from the frame by using a master link from the 70s CB450 twin.

Third and most amazing, the sohc4 forum says the cam chain tensioner screw (4) should never be rotated. As usual, they are wrong. No one who says this could have very much experience with this bike. Note the screw slot. With the engine running--of all the 70s fours, only the 500/550/650 cam chains are adjusted running--one simply loosens the 6mm locknut just enough to free the screw, and then the factory valve adjust tool is used to apply counterclockwise force on the screw until any cam chain noise subsides. Before releasing pressure, the locknut is snugged up using a long 10mm open end wrench.

In fact, how anyone who positions himself as an expert in vintage Hondas could act like this is quite the mystery. The Honda name is alnost synonymous with vintage cam chain tensioners that work poorly. What is plain is that the "experts" on sohc4.com have had deplorably little experience with this model Honda. They're fake experts. They haven't serviced the CB500/550 engine, and just as certainly they have never disassembled it. The rack and pinion design of the tensioner, with its stamped out sheet metal housing, sloppily-mounted pinion gear, relatively wimpy spring, and the one part that every Honda mechanic with even a little experience knows must be removed and thrown away for the tensioner to work its best, just can't do the job on its own. Some experts.