NORTON 850 CommandO MARK 3 Digital Workshop Repair Manual 1975 ONWARDS

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Welcome to the essential guide for the Norton Commando 850 MkIII, a celebrated icon of British motorcycle engineering. Produced from 1975 to 1977, this iteration of the legendary Commando line,...

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Art.-Nr: 124480

Stichworte: 1975 850 CommandO MARK 3 Commando Motorcycle Motorcycles Norton

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Beschreibung

Welcome to the essential guide for the Norton Commando 850 MkIII, a celebrated icon of British motorcycle engineering. Produced from 1975 to 1977, this iteration of the legendary Commando line, powered by its robust 848 cc parallel-twin engine, represents the final evolution of a design renowned for its performance and distinctive styling. The MkIII sought to refine the Commando's already impressive capabilities, offering a compelling blend of power and handling that appealed to riders and enthusiasts alike, cementing its place in motorcycling history. This comprehensive digital workshop repair manual is meticulously designed to cover every aspect of the Norton Commando 850 MkIII. It provides detailed instructions for repair, maintenance, rebuilding, refurbishment, and restoration, suitable for owners, custom builders, and professional workshops. Inside, you will find in-depth guidance on the engine, transmission, fuel, electrical, chassis, suspension, and braking systems, alongside routine maintenance schedules, troubleshooting procedures, and expert-level technical specifications. With high-quality visuals and expert-level detail, this manual is an indispensable resource for ensuring the longevity and optimal performance of your classic Norton.

🏷️ Basic Information

Identification

Make:

Norton

Model:

Commando MkIII

Model Variant:

Generation

Generation Name:

MkIII

Production Start Year:

Codes

Engine Code:

850cc Parallel-Twin (specific internal codes vary by production run)

👋 Introduction

Market Position

Target Audience:

Norton Commando 850 MkIII owners, restorers, custom builders, and independent workshops.

Competitive Analysis

Advantage:

Provides a single, consolidated source of information for all aspects of the motorcycle, often surpassing fragmented factory bulletins or less comprehensive guides. Offers significant cost savings over professional labor.

Key Features

Feature 1:

All repair procedures covered from A-Z.

Feature 2:

High-quality visuals (photos, illustrations, diagrams) for clarity.

Feature 3:

Instant download for immediate access.

Feature 4:

Cross-platform compatibility (Windows and Mac).

📋 Manual Details

Coverage Areas

Coverage Scope:

Comprehensive repair, maintenance, rebuilding, refurbishment, and restoration

Page Count

Estimated Page Count:

Likely extensive, comparable to full factory service manuals, typically 300-600+ pages for this level of detail.

Manual Type

Type:

Digital Workshop Repair Manual

Language

Language:

English

Format

Format:

Digital (downloadable PDF or similar electronic format)

📖 Manual Coverage

Systems Covered

Engine:

Complete engine disassembly, inspection, repair, and reassembly. Covers cylinder heads, pistons, crankshaft, camshaft, valve train, lubrication system, cooling (if applicable), and ignition system.

Transmission:

Gearbox (often a 4-speed or 5-speed depending on specific MkIII variant), clutch, and primary drive system.

Fuel System:

Carburetor tuning and overhaul (likely Amal Concentric), fuel tank, fuel lines, and petcock.

Electrical System:

Wiring diagrams, lighting, ignition, charging system (alternator/generator, regulator), starter motor, battery, and instrumentation.

Chassis And Suspension:

Frame inspection and repair, front fork (Triton-style or standard Commando), rear swingarm, shock absorbers, and steering.

Brakes:

Front and rear brake systems (likely drum brakes, with potential for early disc brake applications on some MkIII variants), brake lines, master cylinders, and calipers/slave cylinders.

Wheels And Tires:

Wheel bearings, spoke replacement, tire fitting, and pressure recommendations.

Bodywork:

Fuel tank, side covers, seat, fenders, and associated mounting hardware.

Procedures Included

Routine Maintenance:

Oil changes, filter replacement, chain adjustment, spark plug replacement, valve clearance checks, brake adjustments, and lubrication points.

Troubleshooting:

Diagnostic guides for common problems, symptoms, and their likely causes, with step-by-step solutions.

Engine Rebuild:

Detailed instructions for complete engine teardown, inspection of wear components, machining specifications, and reassembly.

Transmission Overhaul:

Clutch adjustment and replacement, gearbox disassembly and reassembly, gear selection mechanism repair.

Electrical Diagnostics:

Testing of ignition coil, stator, regulator, and starter motor. Fault finding for intermittent electrical issues.

Suspension And Steering Repair:

Fork seal replacement, damper rod inspection, swingarm bearing replacement, steering head bearing adjustment/replacement.

Brake System Service:

Brake fluid flushing, caliper/wheel cylinder overhaul, pad/shoe replacement.

Carburetor Tuning:

Jetting recommendations, needle height adjustment, idle speed settings for optimal performance and fuel economy.

Frame Straightening And Repair:

Identification of frame damage, alignment procedures, and welding techniques (if applicable).

Technical Depth

Depth:

Expert-level. Covers detailed specifications, tolerances, torque values, and procedures suitable for professional mechanics and experienced restorers.

📊 Manual Specifications

File Format

File Type:

Digital (likely PDF or similar, allowing for searchability and printing)

Print Quality

Image Resolution:

High quality photos, illustrations, and diagrams, enabling clear identification of components and procedures.

Binding Type

Binding:

N/A (Digital Format)

Paper Type

Paper:

N/A (Digital Format)

Usability

Searchability:

High (typical for digital formats, allowing for quick information retrieval)

Printability:

Full print capability for individual procedures or the entire manual.

⚙️ Engine Specifications

Primary Engine

Engine Type:

Air-cooled, 360° crankshaft, parallel-twin

Displacement:

848 cc (Nominal)

Bore X Stroke:

77 mm x 90 mm

Compression Ratio:

Typically 8.0:1 to 8.9:1 (varies with specific MkIII models and piston options)

Valve Actuation:

Pushrod overhead valve (OHV)

Ignition System:

Lucas electronic ignition or contact breaker points ignition, depending on specific variant.

Performance

Horsepower:

Approx. 60-65 bhp at 6,000-6,500 rpm (manufacturer claims vary)

Torque:

Approx. 55-60 lb-ft at 4,000-5,000 rpm (manufacturer claims vary)

Fuel System

Carburetor Type:

Twin Amal MkII Concentric carburetors (common fitment)

Fuel Type:

Unleaded gasoline (preferred) or leaded gasoline, with appropriate octane rating.

Lubrication System

Oil Type:

SAE 20W-50 or 10W-40 motorcycle-specific oil (e.g., Castrol GTX, Motul 3000).

Oil Capacity:

Approximately 4 US quarts (3.7 liters) for engine and primary chaincase.

Oil Filter:

Integrated oil filter within the crankcase, requiring periodic cleaning/replacement.

🔧 Transmission

Standard

Gearbox Type:

Constant mesh, 4-speed or 5-speed (MkIII often features the 5-speed 'Triumph' gearbox adapted)

Clutch Type:

Wet multi-plate, cable-operated

Features

Primary Drive:

Chain-driven, enclosed primary chaincase with oil bath.

📐 Dimensions

Exterior

Wheelbase:

Approx. 56 inches (1422 mm)

Weights

Dry Weight:

Approx. 420-435 lbs (190-197 kg)

Fuel Capacity:

Approx. 4.5 US gallons (17 liters)

🛡️ Safety Features

Ratings

Safety Standards:

Designed to meet 1970s automotive and motorcycle safety standards. Modern safety features are generally absent unless retrofitted.

Active Features

Braking System:

Front and rear drum brakes (later MkIIIs may have front disc brakes). The effectiveness is a common point for upgrades.

Passive Features

Lighting:

Standard headlamp, tail lamp, and turn signals. Bulb types and wattages are detailed in the manual.

💡 Technology Features

Infotainment

Infotainment System:

N/A (Classic motorcycle, no electronic infotainment)

Driver Assistance

Assistance Features:

N/A (No electronic driver assistance systems)

Connectivity

Connectivity Features:

N/A (No electronic connectivity features)

Modern Upgrades Covered

Covered Upgrades:

Manual likely includes guidance or reference for common upgrades like electronic ignition, improved brake systems, and alternative exhaust systems.

🔧 Maintenance

Service Intervals

Oil Change Interval:

Every 2,000-3,000 miles (3,200-4,800 km) or annually, whichever comes first.

Valve Adjustment Interval:

Every 4,000-6,000 miles (6,400-9,600 km).

Chain Lubrication Adjustment:

As needed, or every 500 miles (800 km).

Fluid Specifications

Fork Oil:

Typically SAE 10W or 20W fork oil, capacity specified per fork leg.

Brake Fluid:

DOT 3 or DOT 4 brake fluid (if equipped with disc brakes).

Known Issues

Common Problem 1:

Isolastic mounting system wear and adjustment, leading to vibration and handling issues.

Common Problem 2:

Gearbox oil leaks and occasional shifting issues.

Common Problem 3:

Electrical gremlins, particularly related to the Lucas charging system and wiring harnesses.

Common Problem 4:

Carburetor tuning difficulties and potential fuel delivery issues.

Common Problem 5:

Oil leaks from engine seals and gaskets.

📚 Vehicle History

Brand Heritage

Manufacturer:

Norton Motorcycle Company, a historic British motorcycle manufacturer.

Model Evolution

Commando Lineage:

The Commando line, introduced in 1967, was a highly influential motorcycle known for its 'Isolastic' frame system designed to isolate rider vibration. The MkIII was the final evolution of the original Commando design, attempting to address reliability concerns and introduce modern features like electric start (on some models).

Production

Production Period:

The MkIII was produced from 1975 to 1977, marking the end of the original Commando line before Norton's subsequent financial difficulties.

🏆 Awards & Recognition

Recognitions

Historical Acclaim:

The Norton Commando range, including the 850 MkIII, is widely recognized as a classic British motorcycle, celebrated for its performance and iconic styling. While specific awards for the MkIII are rare, the model line received numerous accolades during its production lifespan for its engineering and riding experience.