**The AJS Twin Models: A Post-War Triumph in Motorcycle Engineering**

The AJS Twin Models, produced from 1949 to 1955, emerged as a testament to the resilience and innovation of the British motorcycle industry in the aftermath of World War II. These motorcycles, known for their rugged construction, reliable performance, and advanced design features, quickly gained a reputation as formidable contenders on both road and track.

**Engine and Transmission**

At the heart of the AJS Twin Models lay a robust 496cc parallel-twin engine, a departure from the company's traditional single-cylinder offerings. The engine featured a cast-iron cylinder block with integral cylinder heads, providing exceptional strength and durability. The short-stroke design (65mm bore x 83mm stroke) favored torque over outright horsepower, resulting in impressive pulling power in all riding conditions.

The engine employed a wet-sump lubrication system with a capacity of 4 pints (2.3 liters), ensuring adequate lubrication even under strenuous riding conditions. The oil pump, located within the primary chaincase, circulated the oil through the engine and gearbox, providing lubrication to all critical components.

The transmission comprised a four-speed gearbox with a kick-start mechanism. The gearshifter, positioned on the right-hand side of the engine, offered smooth and precise gear changes. The primary drive consisted of a duplex chain enclosed within an oil-tight chaincase, providing protection from dirt and wear.

**Chassis and Suspension**

The AJS Twin Models were built upon a sturdy double-cradle frame fabricated from high-tensile steel tubing. The rigid frame design, combined with a telescopic front fork and plunger-type rear suspension, ensured responsive handling and stability.

The front suspension employed leading-link forks with hydraulic damping, offering a comfortable and controlled ride over uneven road surfaces. The rear suspension featured a plunger-type system with adjustable coil-over shocks, providing a smooth and progressive damping action.

**Braking and Wheels**

Braking duties were handled by a 7-inch (178mm) diameter single leading-shoe front brake and an 8-inch (203mm) diameter single leading-shoe rear brake. The brakes provided adequate stopping power, although they lacked the feel and modulation of modern braking systems.

The AJS Twin Models rolled on 19-inch wire-spoke wheels with heavy-duty aluminum rims. The tires, measuring 3.25 x 19 at the front and 3.50 x 19 at the rear, offered a combination of grip and durability on both road and off-road terrain.

**Styling and Features**

The AJS Twin Models exuded a classic, utilitarian aesthetic with a timeless appeal. The round headlight, curved fenders, and saddlebags gave the motorcycles a distinctive and rugged appearance. The chrome-plated fuel tank and exhaust system added a touch of sophistication.

Standard features included a speedometer, tachometer, ammeter, and adjustable handlebars. The motorcycles were also equipped with a passenger seat and footpegs, making them suitable for two-up riding.

**Variants and Legacies**

Over the years, the AJS Twin Models evolved through several variants, including the 16M, 7R, and 18S models. The 16M, introduced in 1949, was the base model and featured a carburetor-fed engine. The 7R, introduced in 1950, was a performance-oriented model with a tuned engine and dual carburetors. The 18S, introduced in 1952, was a more luxurious model with a redesigned frame and suspension, as well as a host of comfort-enhancing features.

The AJS Twin Models played a significant role in the development of British motorcycling. They were reliable, versatile motorcycles that excelled in both solo and sidecar racing, earning numerous podium finishes and earning a reputation for toughness and durability. Today, the AJS Twin Models remain a sought-after classic motorcycle, valued for their historical significance, engineering excellence, and timeless appeal.

Make AJS
Model TWINS
Year 1949-1955
Pages 150
Item MAINTENANCE MANUAL

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CONTENTS
Chapter I. T H E ENGINE · · · · · · · Page 9
Lubrication System—Cleaning Crankshaft Sludge Traps—O.H.V. Rocker Adjustment—IgnitionTiming—Removing and Replacing Timing Gear—Decarbonising—Engine Noises—Engine Overhaul —Removing Engine from Frame—Dismantling Engine—Centre Web—Crankshaft Assembly— Main Bearings—Inspection—Reassembly—Crank-case and Crankshaft—Connecting-rods—CentreWeb—Installing Engine in Frame—Crankshaft Balance—Crankshaft Modification.
II. CARBURATION · · · · · · · 58
Carburetter Function—1950-54 Types—Faults—Pilot-jet Modification—Excessive Petrol Consump-tion—Mixture Bias—Monobloc Carburetter— Faults—Engine Fails to Idle—Heavy Fuel Con-sumption—Carburetter Flooding.
III. TRANSMISSION · · · · · · · 66
Chain Adjustment—Rivet Extractor—Chain Lubri-cation—Gearboxes—C.P. Gearbox Faults—B.52 Gearbox Faults—Dismantling and Reassembling C.P. Gearbox in the Frame—Dismantling and Reassembling B.52 Gearbox in the Frame— Clutches—Operation—Adjustment—Clutch Slip— Removing the Clutch.
IV. FRAME AND FORKS · · · · · · 89
Steering-head Adjustment—Steering Troubles— Wheel Alignment—Teledraulic Suspension—Faults in the Front Forks—Dismantling the Forks —Changing the Fork Springs—Replacing the Oil Seal—Checking the Oil Content—Removing the Front-fork Assembly—Removing a Fork Inner Tube—Rear-suspension Service—Checking Oil Content—Complete Dismantling—Removing the Oil Tank and Battery Carrier.
V. WHEELS AND BRAKES · · · · · · 109
Adjusting Front-wheel Bearings—Dismantling Wheel Bearings—Removing and Refitting Rear Wheel—Dismantling Rear Brake Drum—Backlash in the Driving Studs—Adjusting Rear Wheel

CONTENTS vii
Chapter Bearings—Brakes—Removing and Replacing BrakeLiners—Fitting New Liners—Brake-shoe Adjust-ment—Ineffective Brakes—Brake Squeal. Page
VI. ELECTRICAL AND IGNITION EQUIPMENT Magneto — Lubrication — Adjustment — Cleaning — Removal — Dynamo — Testing — Removal — Regulator — Testing — Cleaning — Cut-out Testing and Adjustment — Burnt Contacts — Sparking-plugs — Ammeter Testing — Battery— Lamp Bulbs Blowing—Removing the Headlamp— Focusing the Main Driving Beam—Wiring Diagrams. · · 119
VII. TUNING FOR SPEED Valve Timing—Valve Springs—Rocker Clearances—Carburation—Exhaust System—Dismantling theEngine—Frame Adjustments—Wheels and Tyres —Chains. · · · · · · 135
APPENDIX I · · · · · · · 140
Periodic Maintenance—Recommended Lubricants.
APPENDIX 2 Technical Data—Spring Data—Gearbox and ChainData. · · · · · · · 142
INDEX · · · · · · · 148·



As motor bikes and or vehicles are made in generations, these manuals are suitable for other years of manufacture

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