Variant Engine:
750 Combat, 850 Mark II, 850 Mark IIA, 850 Mark III (Electric Start)
Production Years Covered:
1970s (specific years depend on Mark II/IIA/III evolution)
Target Audience:
Owners and mechanics seeking to maintain, repair, and restore Norton Commando motorcycles from the early 70s to early 80s.
Value Proposition:
Provides essential technical data and procedures crucial for the upkeep of these iconic British motorcycles, often unavailable in simplified owner's guides.
Uniqueness:
Covers multiple Commando variants including the transition to electric start and engine size increases, offering broad utility for this model range.
Engine:
Engine overhaul, disassembly, assembly, tuning, carburettor adjustment, ignition system, lubrication system, cooling system (air-cooled).
Transmission:
Gearbox disassembly, assembly, troubleshooting, gear selection mechanism, clutch operation and adjustment.
Electrical:
Wiring diagrams, lighting system, ignition system (points, coil, capacitor), starter motor and circuitry (for Mark III), battery maintenance, charging system (alternator/dynamo).
Chassis And Suspension:
Frame inspection and repair, front fork (Roadholder) overhaul, rear shock absorber replacement and adjustment, wheel bearings, steering head bearings.
Brakes:
Front and rear brake system overhaul (drum or disc depending on variant), brake pad/shoe replacement, hydraulic system bleeding (if applicable).
Fuel System:
Fuel tank maintenance, fuel lines, fuel tap, carburettor types (e.g., Amal Concentric) identification, cleaning, and adjustment.
Bodywork And Trim:
Body panel removal and refitting, seat mounting, mudguards, instrument cluster, exhaust system installation.
Routine Maintenance:
Oil changes, chain adjustment, spark plug replacement, air filter cleaning, brake adjustments, lubrication points.
Troubleshooting:
Diagnostic guides for common starting, running, and electrical issues. Symptom-based fault finding.
Major Repairs:
Engine rebuilds, transmission overhauls, suspension component replacement, electrical system repairs.
Special Tools:
Identification and use of specialized tools required for specific tasks.
Depth:
Comprehensive workshop-level detail, suitable for experienced mechanics and dedicated enthusiasts. Includes step-by-step instructions, diagrams, and specifications for complete overhauls.
Searchability:
Likely text-searchable if scanned from a high-quality original, facilitating quick access to information.
Printability:
Designed to be printable for workshop use.
Original Quality:
Dependent on the source scan, but aims to reproduce original factory manual clarity.
Original Binding:
Typically a stapled or perfect-bound booklet for original factory manuals.
Original Paper:
Factory manuals were typically printed on durable paper stock to withstand workshop conditions.
Type:
Air-cooled, OHV parallel-twin
Displacement:
749cc (750 models), 828cc (850 models)
Bore X Stroke:
73mm x 89mm (750), 77mm x 89mm (850)
Compression Ratio:
Approx. 8.0:1 to 8.5:1 (varies by specific model and tune)
Horsepower:
Approx. 50-60 bhp at 6,500 rpm (depending on variant and tuning)
Torque:
Approx. 45-50 lb-ft at 5,000 rpm (depending on variant)
Carburettor:
Typically Amal Concentric (single or twin, depending on model variant and original specification)
Fuel Type:
Unleaded gasoline (modern equivalents with appropriate octane rating recommended, or lead substitute additive for older engines).
Type:
Positive earth, battery-coil ignition with contact breakers (points) and mechanical advance unit.
Type:
Wet sump (integrated with gearbox for earlier models, later models may have separate oil tank/pump arrangements).
Type:
4-speed constant mesh manual gearbox
Variant Options:
While not strictly optional, later Mark III models featured electric start integrated with the transmission/engine casing.
Clutch:
Dry, multi-plate clutch, cable operated.
Gearbox Oil:
API GL-4, SAE 20W-50 motorcycle gear oil recommended.
Crash Test Data:
Not applicable for motorcycles of this era in the context of modern automotive safety ratings.
Braking System:
Disc front brake (Dunlop or Grimeca typically) and drum rear brake on most models. Later models might feature dual disc front. Early models may have drum front brake.
Lighting:
Halogen headlamp, taillight, brake light, and indicator lights.
Oil Change:
Recommended every 2,000-3,000 miles or 6 months, whichever comes first. Check manual for precise intervals.
Valve Clearance:
Typically checked at 2,000-4,000 mile intervals, depending on use and manufacturer recommendations.
Chain Lubrication:
Frequent lubrication is essential, ideally every 500 miles or after riding in wet conditions. Adjustment as needed.
Engine Oil Capacity:
Approximately 4 imperial pints (2.27 litres) for the 850cc engine. Consult manual for specific variants.
Recommended Oil Viscosity:
SAE 20W-50 or SAE 20W-40 motorcycle-specific oil, often with zinc additive (ZDDP) for flat-tappet engines.
Brake Fluid:
DOT 3 or DOT 4 (if hydraulic disc brakes are fitted). Check master cylinder for specific recommendation.
Isolastic System:
Wear in the rubber mounting bushes can lead to increased vibration and handling issues. Regular inspection and replacement are advised.
Oil Leaks:
Common across many vintage motorcycles, particularly around the crankcases, gearbox, and cylinder head. Gasket and seal replacement is often required.
Carburettor Tuning:
Amal Concentric carburettors can be sensitive to altitude, temperature, and wear, requiring regular adjustment for optimal performance.
Electrical Reliability:
Older wiring looms can degrade, leading to intermittent electrical faults. Check for brittle insulation and corroded connections.
Gearbox Selection:
False neutrals or difficulty finding gears can sometimes indicate wear in the gearbox or a misaligned shift drum/cam plate.
Legacy:
Norton is a legendary British motorcycle manufacturer with a long history of innovation and racing success.
Commando Development:
The Commando was a revolutionary motorcycle for its time, known for its 'Isolastic' frame mounting system designed to reduce engine vibration. The 850 models represented an increase in displacement and refinement over the earlier 750 variants, with the Mark III introducing electric start.
Manufacturing Era:
The Commando line was produced from 1967 to 1977, with the variants covered by this manual (750, 850 MkII, IIA, III) falling within the later years of this production run.
Manufacturing Location:
United Kingdom
Historical Impact:
The Norton Commando is widely regarded as one of the most iconic and significant motorcycles of the 20th century, often featured in 'greatest bikes' lists and celebrated for its performance and handling in its era.
Contemporary Reviews:
In its time, the Commando was praised for its powerful engine, refined handling thanks to the Isolastic frame, and sporty performance, though early models faced some quality control issues.
