Norton 850 Commando Mark 3 1975 Workshop & Parts Manual Set (P/N 00-4224)

The workshop manual provides the service procedures, while the illustrated catalog supplies component references, part numbers, and quantities for identifying replacement parts before repair.

Model coverage: The workshop manual is devoted to the electric-start, left-foot-shift Mark 3. Earlier Commando versions require the corresponding earlier publication.

PDF Access, Navigation, and Diagram Detail

Search and wiring detail: PDF text search is not available. Two embedded bookmarks open the workshop manual and parts catalog; they do not provide chapter-by-chapter navigation. Small wiring codes require enlargement, and some lettering around the master-switch connection diagrams remains blurred. Some workshop pages are repeated or out of sequence.

The set is supplied as one printable, 259-page PDF. Both publications’ covers, introductory material, indexes, and the workshop section dividers are included in that total, along with two repeated workshop pages.

Engine Overhaul, Electric Start, and Chassis Service

The following selected topics show the scope of the workshop material. Additional subjects include fuel-tank removal and exhaust-system installation.

• Engine repair: Cylinder-head servicing, valve-guide replacement, decarbonizing, crankcase dismantling, crankshaft inspection and reassembly, and lubrication-system service.

• Primary drive and starter: Diaphragm-clutch work, automatic primary-chain tensioner assembly, starter reduction gears, the sprag freewheel, and the overload backfire device.

• Gearbox overhaul: Removal, gear-cluster dismantling, selector-fork and camplate inspection, countershaft-sprocket replacement, and reassembly of the left-foot-shift transmission.

• Amal carburetors: Type 932 removal, dismantling, component inspection, mixture adjustment, twin-carburetor synchronization, and air-filter servicing.

• Frame and suspension: Adjustable Isolastic mountings, the suspensory head-steady spring, frame checks, swinging-arm rebushing, Roadholder forks, and steering-head bearing replacement.

• Norton-Lockheed brakes: Caliper and master-cylinder overhaul, hydraulic bleeding and flushing, rear-pedal adjustment, wheel-bearing service, and tire removal and fitting.

• Electrical diagnosis: Alternator, rectifier, Zener-diode, ignition-coil, and capacitor tests; Prestolite starter-motor overhaul; wiring diagrams; and Interpol alternating-horn checks.

The workshop manual was written for distributor and dealer staff as well as enthusiastic private owners; major overhaul work assumes suitable tools, facilities, and mechanical knowledge.

Cylinder Head, Crankshaft, and Lubrication

Cylinder-head instructions extend to recutting valve seats after guide replacement and checking valve sealing. The valve-guide tool 063964 is identified, while crankshaft regrind drawings relate journal sizes to replacement bearing shells. Torque references cover engine mounts, cylinder-head fasteners, and crankshaft components in lbf/ft and kg/m.

The dry-sump lubrication material covers the oil pump, pressure-relief valve, crankcase breather, and oil separator. It explains why the Mark 3 anti-leak valve makes pump and feed-pipe priming essential after rebuilding: an unprimed supply risks lubrication damage.

Primary Transmission and Starter Assembly

The primary-drive section distinguishes the rigid gearbox mounting from earlier arrangements. Its sprocket-sleeve alignment and seal-protection guidance addresses a specific repair trap: misalignment can shorten the primary-chaincase oil seal’s life.

Step-by-step procedures cover clutch dismantling with diaphragm-spring tool 060999 and assembly of the starter drive. Illustrations include the primary-chain automatic tensioner exploded arrangement and the starter gear-reduction diagram.

Carburetion, Isolastic Mountings, and Brakes

Mixture checks are organized by throttle opening, with separate guidance for sustained high-altitude operation. Carburetor illustrations identify the jets, needle, float components, and intake connections.

Frame-checking charts support alignment assessment, and the Isolastic sections explain mounting clearances and assembly differences. Girling rear-suspension coverage includes spring and mounting-bush work; the damper units are factory sealed and cannot be serviced.

Brake illustrations include the caliper group and master-cylinder exploded views. Power-unit lifting, fuel handling, and electrical service require secure support, ventilation, and electrical isolation as specified in the manual.

Charging Tests, Market Differences, and Parts Identification

Electrical test diagrams connect meter readings to fault checks for the charging and ignition systems. Separate material explains early warning-light equipment, the Canadian automatic lights-on arrangement, and Interpol horn circuits.

The parts catalog contains 35 illustrated groups with reference numbers, descriptions, quantities, and maker’s or superseded numbers where listed. Variant-specific seats, fuel tanks, handlebars, cables, and hydraulic hoses help distinguish configurations when selecting parts.

Selected Valve-Clearance and Ignition Test Data

Cold valve-clearance data lists 0.006 in. for intake and 0.008 in. for exhaust. The ignition section specifies 28° BTDC at full advance, with stroboscopic checking at 3,000 rpm.

For Lucas 17M6 ignition coils, the electrical chapter gives a primary-winding resistance range of 1.7–1.9 ohms at 20°C. These examples accompany the manual’s component inspection dimensions, adjustment data, and electrical test procedures.