When things are normal, the oil tank maintain a more-or-less consistent level on your dipstick when the engine is running. There is some oil in the filter and the bottom of the engine (about 2/3 quart total) that can remain there unless you purposefully drain both during an oil change (and filter swap). Total engine oil from bone dry (like after a rebuild) on the CB750K0 (diecast) thru CB750K6 is 4.4 quarts. In the later 750 it is 4.1 quarts. Some of the sandcast 750 held only 3.7 quarts total, as they had a thinner oil tank.
If your tank level gets HIGHER after an oil change, it is because there was extra oil left in the bottom end of the engine (the oil pan). In many of these bikes now, the rubber checkvalve that closes off the pump when not running has become real hard an will not seal: this lets oil seep through the pump into the bottom end when the bike is parked after being run (the oil is thin then). It can even drain the whole tank! So, if you drain the tank, always use a container so you can see how much oil comes out - then you can tell if it is still holding the 3 quarts (in your engine) or if some escaped: if it did, then drain the oil pan (bottom end) at the same time. Then install 3 quarts of oil in the tank, start and run for 2-3 minutes, then check the level again. It might need a bit more. The "F" bikes all have the lesser oil amount in their systems (4.1 qts total).
