Oil is delivered by gravity to the feed side of a double gear pump fitted at the bottom of the timing case and driven by a skew gear on the crankshaft. The supply from the pump is fed through an oil way and to a pipe cast in the timing cover where it is divided, a portion of the supply being taken direct to the rocker bearings, the remainder being delivered through the hollow crankshaft direct to the centre of the crankpin. The oil passes right through the roller bearing big end and is thrown off to lubricate the cylinder, piston and the crankshaft main bearings, etc., ; that portion of the supply which is taken to the rocker bearings lubricates the rocker spindles, and, by means of oil grooves, passes out of the ends of the bearings to lubricate the push rod ball ends, etc. Oil mist is blown through the hollow rockers to lubricate the valves and guides. The oil, falling by gravity down the push rod cover, collects in the timing case up to a predetermined level, enabling the timing gears to dip into it and carry it round over the gears, the cams and cam followers. The excess oil flows into the oil sump through a hole in the partition between the crankcase proper and the timing case, and, after draining down to the sump, is taken back to the oil tank by the return half of the oil pump. An efficient filter is incorporated in the oil tank to prevent foreign matter circulating with the oil. An efficient scraper ring is fitted to the piston to prevent oil reaching the combustion chamber. Never keep the oil in circulation too long. Drain the oil from the tank at least once every 1,000 miles and fill up with fresh oil. With a new Machine we recommend changing the oil first at not more than 500 miles, once every 2,000 miles unscrewing the oil feed union from the bottom of the oil tank—the filter is attached to this union and screws out of position with it. The crankcase drain plug is fitted in the bottom of the crankcase right underneath and between the frame tubes. Clean the oil tank and the filter first in paraffin and then in clean petrol or benzol and allow to dry thoroughly before replacing and refilling up with fresh oil. Do not under any circumstances flush out the engine with paraffin. If it is desired to flush it out this may be done using one of the numerous flushing oils which are on the market.
It is a good plan after having changed the oil to leave the return pipe to the tank disconnected, the engine can then be started and it will be found that dirty oil will be pumped up through the pipe, this can be caught in a suitable container and the engine should be run until clean oil is seen to issue. The engine should then be stopped and the pipe connected up again to the tank. This is easier and better than attempting to flush out the engine.