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My 1936 500cc BSA Q8 Empire Star and the 1935 500cc BSA W35-7 have split port single cylinder engines, both utilize a sort of half way house design between vintage and more modern oil delivery systems. The oil is pumped to the engine big end via a crank driven gear pump, the flow rate can be manually adjusted. However, there is no pump to recover the oil back to the oil tank. The oil tank is cast into the engine crankcase at the front of the engine, as the crankshaft rotates the (large) crank webs picks up the oil from the bottom of the crankcase, the oil is then scraped off the crank by a knife edge design at the top of the crankcase oil tank, thus returning the oil back to the oil tank. It works well. The only other direct gear pump oil supply is to the rear inlet valve area, which has it own cover, the front exhaust valve is exposed and has to be lubricated by hand periodically. All other internal engine lubrication is by splash feed.
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