🏷️ Basic Information

Make:

KTM

Model:

LC4 400/660

Years Covered:

1998-2005

Product Type:

Repair Manual

Engine Code:

LC4 (Liquid Cooled Four-stroke)

👋 Introduction

Positioning:

KTM's LC4 platform represented a significant step in off-road and dual-sport performance, targeting riders seeking robust, powerful single-cylinder engines with advanced chassis dynamics. This era of LC4 bikes built upon KTM's racing heritage.

Competitors Era:

Competed with other high-performance single-cylinder off-road and dual-sport motorcycles from manufacturers like Yamaha (WR series), Honda (XR series), Suzuki (DR-Z series), and Husqvarna.

Features Of Lc4 Platform:

Powerful single-cylinder engine, robust chassis, advanced WP suspension, excellent off-road capability, and reasonable on-road manners for dual-sport variants.

📋 Manual Details

Comprehensive Coverage:

Complete Repair and Maintenance

Estimated Page Count:

300-500 (typical for comprehensive manuals of this era)

Type:

Factory Service Manual / Workshop Manual

Purpose:

Repair Manual (also known as Service Manual or Workshop Manual) - intended for technical repair and maintenance procedures.

Language:

English (most likely, though multi-language versions exist)

Format:

Printed Manual (or high-quality PDF scan)

📖 Manual Coverage

Engine:

Engine disassembly, assembly, tuning, troubleshooting, internal components (pistons, rings, valves, camshafts, crankshafts, etc.)

Fuel System:

Carburetor (Mikuni BST variants typical for LC4) or Fuel Injection (if applicable to later models), fuel pump, fuel lines, tank, filters

Ignition System:

CDI ignition, spark plugs, ignition coils, wiring diagrams

Cooling System:

Radiator, cooling fan, coolant hoses, thermostat, water pump

Transmission Drivetrain:

Gearbox operation, clutch (hydraulic or cable), shifting mechanisms, chain drive, sprockets

Suspension:

Front forks (WP USD), rear shock absorber (WP or Sachs), linkage systems, seals, oil specifications

Brakes:

Front and rear brake systems (disc brakes, hydraulic calipers), master cylinders, brake lines, fluid specifications (DOT 4 typical)

Electrical System:

Wiring harnesses, battery, starter motor, alternator/stator, lighting, switches, fuses, troubleshooting charts

Chassis Frame:

Frame inspection, welds, headstock bearings, swingarm, wheel bearings

Bodywork Trim:

Fairings, seat, fenders, fuel tank, exhaust system installation/removal

Clutch Mechanism:

Detailed procedure for clutch plate replacement, basket inspection, and hydraulic actuator service.

Exhaust System:

Removal, installation, and common issues related to exhaust headers and mufflers.

Maintenance:

Routine checks, oil changes, filter replacements, chain maintenance, brake bleeding, spark plug replacement, valve clearance adjustment

Troubleshooting:

Diagnostic procedures for common and uncommon issues, symptom-based troubleshooting guides

Repair Rebuild:

Step-by-step instructions for component disassembly, repair, and reassembly, including complete engine and transmission overhauls

Specifications Data:

Torque specifications, clearances, tolerances, fluid capacities, electrical component data

Wiring Diagrams:

Detailed electrical schematics for all systems

Suspension Rebuild:

Step-by-step guide for fork seal replacement, oil changes, and rear shock servicing, including specific oil types and quantities.

Depth:

Comprehensive, suitable for professional mechanics and advanced DIY enthusiasts

Diagnostic Charts:

Includes detailed troubleshooting charts for electrical and mechanical issues, helping to pinpoint problems efficiently.

📊 Manual Specifications

Digital Format Details:

Searchable text, high-resolution images, printable pages (if PDF)

Print Quality:

High-quality, durable paper stock with clear diagrams and text

Binding:

Spiral-bound or perfect-bound for lay-flat usability in a workshop environment

Paper Type:

Glossy or semi-gloss paper for durability and image clarity

Coverage Scope:

Designed to cover all repair and maintenance aspects from basic service to complete engine and gearbox rebuilds.

⚙️ Engine Specifications

Engine Type:

4-stroke, single-cylinder, liquid-cooled, SOHC or DOHC (depending on specific 400/660 variant)

Displacement 400:

Approximately 398cc

Displacement 660:

Approximately 659cc

Bore Stroke 400 Approx:

Specifics vary, but typically around 88mm x 66.2mm

Bore Stroke 660 Approx:

Specifics vary, but typically around 101mm x 80.4mm

Horsepower Range:

Estimates vary widely based on model and tuning, but expect figures from 40-55+ hp for the 400 and 50-65+ hp for the 660. Specific dyno charts would be in the manual.

Torque Range:

Torque figures would be substantial for a single cylinder, likely in the 30-45 lb-ft range. Specific figures would be in the manual.

Carburetion:

Typically Mikuni BST-40 or similar flat-slide carburetors on earlier models, or Keihin FCR on later or performance variants. Fuel injection began appearing in later iterations or specific models.

Fuel Type:

Unleaded Gasoline, Octane Rating 91 (RON+MON)/2 = 87 AKI minimum.

🔧 Transmission

Gearbox Type:

5-speed or 6-speed constant mesh gearbox

Clutch Type:

Hydraulically actuated wet multi-plate clutch is common.

Final Drive:

Chain drive (520 or 525 pitch typical)

📐 Dimensions

Wheelbase Range:

Approx. 1460-1510 mm (57.5-59.5 inches), varies by model and suspension setting.

Dry Weight Range:

Approx. 130-150 kg (287-330 lbs), depending on model and equipment (e.g., Duke vs. Adventure variants).

Wet Weight Estimate:

Approx. 145-165 kg (320-365 lbs) with fluids.

🛡️ Safety Features

Crash Safety:

Motorcycle safety ratings are not standardized in the same way as cars. Focus is on rider protection through chassis design and component integrity.

Braking System:

Powerful hydraulic disc brakes front and rear, designed for effective stopping power in varied conditions. ABS was not common on this era's off-road/dual-sport bikes.

Frame Design:

Steel trellis frame for rigidity and strength, crucial for off-road riding and stability.

💡 Technology Features

Infotainment System:

Basic instrumentation (speedometer, tachometer, odometer, basic warning lights). No integrated infotainment systems as per modern standards.

Driver Assistance Features:

None (this is a performance-oriented motorcycle, not a car with driver assistance).

Connectivity Options:

None.

🔧 Maintenance

Oil Change Interval:

Typically every 3,000 - 6,000 km (2,000 - 4,000 miles) or annually, whichever comes first. Refer to manual for exact intervals based on usage.

Valve Clearance Check:

Usually around 5,000 - 10,000 km (3,000 - 6,000 miles). Crucial for performance and longevity.

Engine Oil Type:

JASO MA, API SG or higher, SAE 10W-50 or 15W-50 motorcycle-specific oil is commonly recommended. Exact viscosity depends on climate. Manual will specify.

Engine Oil Capacity:

Approximately 1.6 - 2.0 liters (1.7 - 2.1 US quarts) with filter change. Manual is definitive.

Coolant Type:

Ethylene glycol-based antifreeze coolant, typically a 50/50 mix with distilled water. Manual will specify color and type.

Brake Fluid Type:

DOT 4 or DOT 5.1 hydraulic brake fluid. Manual will specify.

Common Wear Items:

Clutch plates, water pump seals, starter motor brushes, fork seals, valve stem seals, cam chain tensioner, carburetors can require periodic adjustment/rebuild.

Electrical Gremlins:

Wiring harness chafing or poor connections can occur with vibration and off-road use. Manual's electrical troubleshooting section is vital.

Engine Longevity:

The LC4 engine is robust but requires diligent maintenance, especially oil changes and valve adjustments, to ensure long life. Overheating can be an issue if cooling system is not maintained.

📚 Vehicle History

Ktm Legacy:

KTM has a strong heritage in off-road racing, dating back to the 1950s. The LC4 platform capitalized on this expertise, bringing competitive performance to production bikes.

Lc4 Development:

The LC4 engine family was a cornerstone for KTM, evolving significantly throughout the 1990s and early 2000s. Models like the EXC (enduro), LC4 Adventure (dual-sport), and Duke (naked streetfighter) shared this versatile engine.

Manufacturing Location:

Primarily Austria, with potential assembly in other global locations.

🏆 Awards & Recognition

Motorsport Achievements:

KTM's LC4 platform has a strong history in various forms of off-road racing, including rallies and enduro events, showcasing its performance capabilities.

Performance Reviews Era:

Contemporary reviews often praised the LC4's torquey engine, capable suspension, and off-road prowess, while sometimes noting its vibration and the required maintenance diligence.