Norton Commando Workshop Manual

## Engine/Primary Transmission

# C

### SECTION C21

### ENGINE LUBRICATION SYSTEM

The Commando lubrication system is of the dry sump type, oil contained in the separate oil tank being fed through a wire strainer by gravity and by suction through the feed side of the gear type oil pump to the crankshaft. The oil pump delivers lubricant under pressure to the oil pressure relief valve and a bleed off the main feed supplies lubricant to the rocker gear. The main oil supply is delivered through the end of the crankshaft, (which is sealed by a garter type scal in the timing cover) to both big ends and escapes between the big end shells and crank journals to lubricate the cylinder walls, main bearings, camshaft and cam followers by splash. Oil collects in the crankcase sump, the inlet rocker box draining through a drill way in the cylinder barrel, and the exhaust rocker box draining through a drill way into the push rod tunnel and providing additional lubrication whilst returning to the crankcase between the cam followers to the camshaft.
The return side of the oil pump draws oil from the sump via the sump filter (or collecting area in later crankcases) and returns it to the oil tank. A bleed from the oil tank return pipe at the tank lubricates the rear chain via a regulator comprising a plastic tube and felt insert.

### SECTION C22

### OIL PRESSURE RELIEF VALVE

The relief valve is fitted to prevent oil pressure rising above 45/55 Ibs. sq. inch. It is fitted to the rear of the timing cover below the rocker oil feed pipe banjo. The valve consists of a spring loaded steel sleeve pre-set at the factory using shims to requlate the blow off pressure and the valve requires no attention. Oil escaping from the valve returns to the feed side of the pump.

### SECTION C23

### CRANKCASE BREATHER

A timed and ported mechanical crankcase breather is usad prior to 1972. In this design, a rotary disc with cut-away segment driven by the camshaft and backed with a light spring mates with a similar stationary disc fitted behind the left camshaft bush in the crankcase. An elbow with flexible pipe from the left crankcase leads to the oil tank. The oil tank breather is connected to the air filter back plate. 1972 models and later have a non-mechanical crankcase breather which is located on the back of the left crankcase and comprises a microcellular foam insert held in position by concave washers. The breather pipe is attached to the top of the breather outlet and the other end to the top of the oil tank. As with previous models the oil tank breather is connected to the air filter back plate.

### SECTION C24

### OIL PUMP

The oil pump is of the gear type and is shown in detail in Fig. C29. The return side of the pump, which is of twice the capacity of the scavenge to provide sufficient capacity to keep the crankcases clear of surplus oil, is identified by the wider gears. The oil pump is sealed to the timing cover bore with a conical rubber oil seal located on the pump body by a steel ferrule and compressed by the timing cover. Removal of the oil pump is included in Section C16 and the servicing routine covered in Section C25.

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