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Lubrication

Lubrication

How It Works

On the timing-side of the engine, beneath and to the rear of the timing chest, is a large hexagon-headed brass plug which seals the pump sleeve flange down on to the crankcase. Within this sleeve there is a reciprocating steel plunger operated by a spur gear which is driven by the oil pump worm on the mainshaft. The rotary movement is used to produce axial motion by means of a scroll groove formed in the plunger. This engages with a fixed, hardened steel peg let into the crankcase wall. One end of the plunger act as a feed pump, the other as a scavange. The pump plunger (OP30) can be withdrawn with a ¼in. B.S.F. bolt after removing the scroll screw, the head of which is punch-locked. The sleeve can be extracted and renewed; sleeves and plungers are supplied only as mated pairs. 

There is a banjo union in the feed line secured by a hollow bolt (A22). On either side of this banjo there should be a 'Klingerit' washer (A27). Three such bolts are used in the twin-cylinder oil lines and one in the breather pipe. Drain the oil from the bottom of the feed line (the thicker one of the two) taking care that an airlock is avoided - do not tighten the bolt until fresh lubricant has been allowed to run through. Light-alloy feed bolts replace the early steel variety, so minimizing the risk of stripping threads in the crankcase. 

The felt filter element, located below the magneto, should be changed every 8,000 or 10,000 miles. Make certain that the pressurising plate seats squarely on the element. Soak a new element in engine oil; fit it, and lay the machine over to fill the chamber before the plug is replaced, so reducing to a minimum the period during which no oil is being delivered to the engine. Oil flows via the hollow feed bolt (A22/1) below the magneto into the timing cover. This bolt has a washer beneath it. It is similar to, but longer than, the other bolts. Within the cover, the oil follows two routes: some passes to the big-end quill and relief valve. The quill must be kept clear and renewed when wasted. At its end is a small screw by which to check that oil is reaching this point.

Oil Control Jets

The remainder of the oil flows vertically up the timing cover to a jet holder which meters the feed to the cylinders and camshafts. Reduction of the standard Amal jet used at this point to cut down the cylinder feed will also reduce the camshaft supply. Too big a jet will starve the big-end side. The best compromise is a 170 jet, though a persistent 'oil-burner' can be cut down as low as 140. Many riders go up to 180 or 190 during running-in to bleed a little more through the piston skirts. The holder is simply screwed into place; it is finally sealed by an acorn nut (OP40). No washer is used. 

Oil eventually finds a way down into the bottom of the sump wherein is located a small compartment of which one wall forms a flywheel scraper blade. The scavange pump keeps the compartment, and, therefore, the sump, dry. It returns lubricant by way of the overhead rocker feeds which bleed off oil according to the size of the orifices in the feed bolts. 

The tank has an effective capacity of five pints. On 'B' and 'C' models the level should be maintained so that the crossbar directly below the filler cap is kept covered. Returning oil issues from an orifice in the neck of the tank. A check on the flow at this point shows whether the pump is working, but it does necessarily prove that the big-ends are being supplied. 

Beside the return orifice is an adjusting screw, bleeding to a pipe at the rear of the tank to direct lubricant to the rear chain. The setting is determined by experiment; one turn open is a good starting basis but it may be necessary to screw it right down to reduce the flow to an acceptable level. 

Because the 1,000 cc. engine is a large one, working easily, the oil may not get as hot as it will in other power units. This may mean that combustion impurities are not evaporated quickly, especially on stop-start running. In these conditions, the oil-change interval should be 1,000 miles. Otherwise an interval of 1,500 to 2,000 miles is in order. A sump drain plug, threaded ¼in. B.S.F. is located in the left engine plate. The addition of colloidal graphite to all mineral oils is permissible.

Gearbox Lubrication

The gearbox is lubricated by splash, the box holding two pints. This brings the level to the bottom of the flat on the dipstick. To assist in determining the quantity of fresh oil to be added when the level is so low that it does not reach the standard dipstick, a home-made slick with a longer flat should be used-provided that the level mark is made in the right place, i.e. measured from under the head of the dipstick. The drain plug of the 1,000 c.c. gearbox is fitted horizontally behind the pivot plate. It is threaded ¼in. B.S.P. The change interval is 5,000 to 10,000 miles. 

Lubrication notes for the 'Comet' and 'Meteor' gearboxes, of Burman pattern, are dealt with under the section 'Transmission'. 

Engine-grade oil is used in the primary chaincase of all models, the case having a ¼in. B.S.F. level plug. No drain plug is fitted to the twins. The oil should be changed at least every 10,000 miles as there is a tendency for condensation to take place. This may result in sludge formation. 'Filtrate' market a sludge-inhibitor capsule especially for this machine. Too much oil may cause clutch slip. 

The speedometer cable should be oiled very lightly at the lower end every 10,000 miles. Too much lubricant too high up the cable inevitably results in dirty marks appearing on the mileage recorder numerals. 

The speedometer gearbox located in the front wheel can be greased with one stroke of the gun every 2,000 miles. Vigorous greasing will flood the hub and impair braking. Inside the hub are two gears. One is a simple interference fit on the hub itself and drives the spur gear attached to the gearbox. No lubrication is required for these gears. 

On the 'Black Shadow' a subsidiary gearbox is used on the back of the 5-in. head. No oil is needed. Cable breakage can usually be attributed to an early type of this gearbox and can occur if the machine is wheeled backwards, causing the cable to run the reverse way.