I've gathered 5 CB750 pumps to try stuff like this with them, this winter. This pump is a 2-section, where the primary pulls oil from the tank and feeds the main journal. The second section scavenges the crankcase, then splits the output between the transmission shafts and the oil tank return.
My goal is to make a high-flow CB750 pump with a bit more pressure in commuter traffic. It's a selfish goal, for my bike, but the results will probably end up here at SOHC4 and in my upcoming 750 book...
The largest issue in these particular pumps: seals and O-rings, as Honda has never supplied the seals as a replacement part. The O-rings were changed (sizes) many times by Honda over the years (many K0 bikes had no locating dowels, some (2) actually got to Spring Honda in 1970 without O-rings, making a mess of a blue-green and a red 750K0
). The version found in the late K2 engines seemed to be where they finally settled on an O-ring size (with dowels) that made them hapy, and didn't leak.
The next issue: dirt enters the scavenge side and chews up the rotor-cover interface, losing tranny-scavenge pressure and flow. Third issue: similar wear on the main feed side.
The inlet/outlet tract on the 750 pumps isn't amenable to the technique shown above, but I wonder about the 500/550 pumps? Certainly the 500, in particular, could benefit.
