You can see from this reproduction of the parts book how unusual the CB500/550 Four cam chain arrangement is. In fact 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. Sohc4 says the cam chain tensioner screw (4) should never be rotated. As usual, they are way off. No one who says this could have very much experience with these bikes. There actually is a special factory tool that fits the screw and adjusts the cam chain.