KTM 640 DUKE II 2003 User Manual (English)

Questions and Answers:

S
Sheila FloresAug 15, 2025
Why is my KTM 640 DUKE II 2003 Motorcycle engine overheating?
- T
  Tracy CampbellAug 15, 2025
  Your KTM Motorcycle engine may be overheating due to several reasons. It could be caused by insufficient cooling liquid, in which case you should replace the cooling liquid and use antifreeze. Dirty radiator fins can also cause overheating, so clean the radiator with a water jet. Other potential causes include a bent radiator hose (shorten or replace it), a defective thermostat (remove and check it), a blown fan fuse (replace the fuse), a defective thermoswitch, or a defective fan (check if it operates properly).
A
Amber DixonAug 18, 2025
What to do if my KTM 640 DUKE II 2003 engine doesn’t crank?
- T
  Tommy LynchAug 18, 2025
  If your KTM Motorcycle engine doesn’t crank, it could be due to an operating error. Ensure the ignition is on, the gear is in neutral, and the emergency OFF switch is off. Another cause could be a discharged battery; in this case, recharge the battery and investigate the cause of the discharge. A defect in the ignition lock or emergency OFF switch may also be the reason.
T
Thomas AndersenAug 21, 2025
Why won't my KTM Motorcycle engine reach full power?
- J
  Jason RichardAug 21, 2025
  Several factors can prevent your KTM Motorcycle engine from reaching full power. A partially interrupted fuel supply or a dirty carburetor could be the cause; clean and check the fuel system and carburetor. Other potential causes include a leaking float (replace the float), a defective membrane of the slide (replace the membrane), a leaking carburetor (check vacuum and venting hoses), a very dirty air filter (clean or replace it), valve clearance being too small (have it adjusted), loss of compression due to the hand decompressor having no play (check the hand decompression cable setting), or faulty electronic ignition timing (have the ignition system checked).
J
Jeffrey SmithAug 25, 2025
What to do if my KTM 640 DUKE II 2003 engine fails to idle?
- P
  Paula ArnoldAug 25, 2025
  If your KTM Motorcycle engine fails to idle, the issue might be a clogged idling jet. In this case, disassemble the carburetor and clean the jets. It could also be due to incorrect adjustment of the adjusting screws on the carburetor, so have the carburetor adjusted. Other possible causes are a defective spark plug (replace it) or a defective ignition system (have it checked).
C
Crystal CookAug 27, 2025
Why does my KTM 640 DUKE II 2003 Motorcycle have high oil consumption?
- C
  Charles MorganAug 27, 2025
  High oil consumption in your KTM Motorcycle could be due to a buckling gear ventilation hose; readjust or replace the ventilation hose. It could also be caused by an engine oil level that is too high; check the engine oil level when the engine is warm and correct if necessary. Another reason might be that the engine oil is too thin (viscosity); use a thicker engine oil.
M
mary25Aug 30, 2025
What to do if my KTM 640 DUKE II 2003 Motorcycle headlight and parking light fail?
- C
  Cynthia LoganAug 30, 2025
  If the headlight and parking light on your KTM Motorcycle fail, the most likely cause is a blown fuse. Replace fuse (3).
K
Kimberly ParkerSep 2, 2025
What to do if flasher lights, brake light, fan and horn fail on KTM 640 DUKE II 2003 Motorcycle?
- A
  Angela WrightSep 2, 2025
  If the flasher lights, brake light, fan, and horn fail on your KTM Motorcycle, it is likely due to a blown fuse. Replace fuse (2).
N
Nathan ParsonsSep 5, 2025
What to do if my KTM 640 DUKE II 2003 battery is discharged?
- Z
  Zachary BentonSep 6, 2025
  If your KTM Motorcycle battery is discharged, it could be because the ignition (power consumer) hasn’t been switched off. Recharge the battery. Another reason might be that the battery isn’t being charged by the generator.
M
Michael TaylorSep 8, 2025
What to do if my KTM 640 DUKE II 2003 engine doesn't crank and the neutral indicator lamp doesn't light up?
- K
  Kevin HarrisonSep 8, 2025
  If your KTM Motorcycle engine doesn't crank and the neutral indicator lamp doesn't light up, it could be due to a blown fuse in the safe-starting system or a blown main fuse. In either case, replace fuse (1). If the fuse blows again, contact a KTM dealer.

KTM 640 DUKE II 2003 Specifications

General

Brand	KTM
Model	640 DUKE II 2003
Category	Motorcycle
Language	English

Summary

Consumer Information for Australia

Consumer information regarding noise control systems for Australia.

Introduction to Your KTM Motorcycle

Congratulates the owner and highlights the importance of reading the manual.

Limited Warranty and Guarantee Information

Details on warranty, usage, and maintenance to maintain coverage.

Serial Number Locations

Chassis and Engine Number Identification

Location of the frame and engine serial numbers.

Operation Instruments: Controls

Control Levers Overview

Explains clutch, decompression, and choke levers.

Operation Instruments: Dashboard

Speedometer, Tachometer, and Indicator Lamps

Explains dashboard instruments and warning lights.

Operation Instruments: Switches

Combination and Starter Switches

Covers combination switch and starter tip switch functions.

Operation Instruments: Engine Controls

Fuel Tap and Shift Lever Operation

Explains fuel tap positions and shift lever operation.

Operation Instruments: Suspension Adjustments

Fork and Shock Absorber Damping

Explains fork and shock absorber damping adjustments.

General Tips and Warnings for Starting

Initial Operation and Running-In

Guides for first rides and engine break-in procedures.

Driving Instructions: Pre-Start Checks

Pre-Start Checks for Safe Driving

Lists essential checks to perform before starting the motorcycle.

Driving Instructions: Starting Procedures

Starting the Engine Cold

Step-by-step guide for starting a cold engine.

Driving Instructions: Riding and Braking

Shifting Gears and Braking Techniques

Guidance on shifting, riding, and proper braking.

Driving Instructions: Stopping and Refueling

Stopping, Parking, and Refueling Procedures

Procedures for stopping, parking, and refueling the motorcycle.

Ignition Curve Adjustment for Low-Octane Fuel

Adjusting Ignition Curve for Low-Octane Fuel

How to change the ignition curve for different fuel octanes.

Periodic Maintenance Schedule

Periodic Maintenance Schedule Overview

Outlines maintenance tasks and intervals for the motorcycle.

Maintenance Work: Chassis and Engine

Removing and Securing the Seat

Instructions for removing and refitting the motorcycle seat.

Maintenance Work: Fork and Steering

Steering Head Bearing Adjustment

How to check and adjust the steering head bearing for play.

Maintenance Work: Rear Suspension

Shock Absorber Spring Preload Adjustment

How to adjust the spring preload on the shock absorber.

Maintenance Work: Chain System

Checking and Correcting Chain Tension

Steps to check and adjust the motorcycle's chain tension.

Brake System: General Information

KTM Disc Brake Overview

General information on front and rear disc brake systems.

Brake System: Front Brake Maintenance

Checking and Refilling Front Brake Fluid

Procedure for checking and adding front brake fluid.

Brake System: Rear Brake Maintenance

Checking and Refilling Rear Brake Fluid

Procedure for checking and adding rear brake fluid.

Wheel Maintenance: Front and Rear Wheels

Dismounting and Mounting the Front Wheel

Step-by-step guide for removing and installing the front wheel.

Electrical System: Battery

Battery Maintenance and Charging

Instructions for battery care, removal, and charging.

Electrical System: Fuses and Lighting

Main Fuse and Fuse Box Location

Explains the main fuse and location of the fuse box.

Cooling System: Components and Checks

Cooling System Overview

Explains the function of the cooling system and its components.

Cooling System and Air Filter Maintenance

Cleaning the Air Filter

Steps for removing, cleaning, and oiling the air filter.

Engine Controls and Oil Level Check

Checking Engine Oil Level

How to check the engine oil level.

Engine Oil and Filter Maintenance

Changing Engine Oil and Screen Filter

Steps for changing engine oil and fine screen filter.

Troubleshooting: Engine Starting Issues

Engine Does Not Crank or Start

Common causes and remedies for engine starting problems.

Troubleshooting: Engine Performance Issues

Engine Fails to Idle or Rev High

Diagnosing and fixing issues with engine idling and revving.

Troubleshooting: Engine Overheating

Engine Overheating Causes and Solutions

Addressing overheating due to cooling system or fan issues.

Cleaning and Winter Storage

Motorcycle Cleaning Procedures

Guidelines for cleaning the motorcycle safely.

Storage and Re-initiation After Storage

Motorcycle Storage Instructions

Procedures for long-term storage of the motorcycle.

Technical Data: Engine Specifications

Engine Specifications Overview

Detailed specifications for the 640 Duke II engine.

Technical Data: Chassis Specifications

Frame, Fork, and Suspension Specs

Technical details on the frame, fork, and suspension components.

Tightening Torques - Chassis

Chassis Fastener Torque Values

Specifies torque values for various chassis fasteners.

Wiring Diagram

Electrical System Wiring Diagram

Electrical system wiring diagram for the 640 Duke II.

Appendix: Component Glossary

Component Glossary (Multi-language)

Glossary of motorcycle components in multiple languages.

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KTM 640 DUKE II 2003 User Manual

Table of Contents

Questions and Answers:

KTM 640 DUKE II 2003 Specifications

Summary

Consumer Information for Australia

Consumer Information for Australia

Introduction to Your KTM Motorcycle

Introduction to Your KTM Motorcycle

Limited Warranty and Guarantee Information

Limited Warranty and Guarantee Information

Serial Number Locations

Chassis and Engine Number Identification

Operation Instruments: Controls

Control Levers Overview

Operation Instruments: Dashboard

Speedometer, Tachometer, and Indicator Lamps

Operation Instruments: Switches

Combination and Starter Switches

Operation Instruments: Engine Controls

Fuel Tap and Shift Lever Operation

Operation Instruments: Suspension Adjustments

Fork and Shock Absorber Damping

General Tips and Warnings for Starting

Initial Operation and Running-In

Driving Instructions: Pre-Start Checks

Pre-Start Checks for Safe Driving

Driving Instructions: Starting Procedures

Starting the Engine Cold

Driving Instructions: Riding and Braking

Shifting Gears and Braking Techniques

Driving Instructions: Stopping and Refueling

Stopping, Parking, and Refueling Procedures

Ignition Curve Adjustment for Low-Octane Fuel

Adjusting Ignition Curve for Low-Octane Fuel

Periodic Maintenance Schedule

Periodic Maintenance Schedule Overview

Maintenance Work: Chassis and Engine

Removing and Securing the Seat

Maintenance Work: Fork and Steering

Steering Head Bearing Adjustment

Maintenance Work: Rear Suspension

Shock Absorber Spring Preload Adjustment

Maintenance Work: Chain System

Checking and Correcting Chain Tension

Brake System: General Information

KTM Disc Brake Overview

Brake System: Front Brake Maintenance

Checking and Refilling Front Brake Fluid

Brake System: Rear Brake Maintenance

Checking and Refilling Rear Brake Fluid

Wheel Maintenance: Front and Rear Wheels

Dismounting and Mounting the Front Wheel

Electrical System: Battery

Battery Maintenance and Charging

Electrical System: Fuses and Lighting

Main Fuse and Fuse Box Location

Cooling System: Components and Checks

Cooling System Overview

Cooling System and Air Filter Maintenance

Cleaning the Air Filter

Engine Controls and Oil Level Check

Checking Engine Oil Level

Engine Oil and Filter Maintenance

Changing Engine Oil and Screen Filter

Troubleshooting: Engine Starting Issues

Engine Does Not Crank or Start

Troubleshooting: Engine Performance Issues

Engine Fails to Idle or Rev High

Troubleshooting: Engine Overheating

Engine Overheating Causes and Solutions

Cleaning and Winter Storage

Motorcycle Cleaning Procedures

Storage and Re-initiation After Storage

Motorcycle Storage Instructions

Technical Data: Engine Specifications

Engine Specifications Overview

Technical Data: Chassis Specifications

Frame, Fork, and Suspension Specs

Tightening Torques - Chassis