Oil Tank: Why do all air-cooled Harley single and twin cylinder bikes have a separate tank for the engine lubricant?

Harleys do not bunker the engine oil in a wet sump like cars or competing motorcycle brands do. Due to engine design there's no space. Instead there's a separate tank, that was housed in the same tin canister as the gas tank. You can tell this design apart from all later makes by the manual oil pump and its pull-and-push knob on top of the oil tank. From the second half of the 1930es on, the motor oil was store in a separate container. On the 750 cc models the complete right half of the split tanks was reserved for the oil, the big Twins got that legendary oil tank under the seat area, between rear wheel and rear cylinder that soon enough gained the name of horseshoe. Only later model design of the 50es to the 70es (Sportster, Eletra Glide, FXR) came up with more and more model-specific oil tanks. In the beginning 90es the oil tanks started to sort of disappear again, as the engine oil was bunkered down in the cellar, in a separate compartment of the gear box. First were the Dynas, then from the 2000s on the Tourting models and last but not least the Softails from 2018 on. Only the good old air-cooled Sportsters retained their separate oil tanks until the very end of the model series.

Oil tanks, oil tank mount and all that stuff

Oil tanks fro and on Harleys have supports and latches. Moreover there are base plates, silentblocs and other kinds of rubbers that kill vibrations, mounting screw kits and many pieces more to prevent the oil tank to fall from the frame. And, of course, not every Harley-Davidson that one might meet on the streets has a stock oil tank. So one may need a certain choice on more or less universal straps and mounts to keep away from the dead end streets of custominzing.

What else does one need to connect an oil tank?

Tubes and tubings to connect them to the engine, oil coolers to keep the lubricant from thermal stress, oil temperature and pressure gauges for consciousness's sake, and filters to keep residues and debris from circulating in the engine.

Just to grant a long life to the best of all Harley-Davidsons — yes, exactly: yours!