KTM 250 400 450 520 525 SX MXC EXC RACING 2000 2001 2002 2003 FACTORY SERVICE REPAIR MANUAL + WIRINGS

KTM 250 400 450 520 525 SX MXC EXC RACING 2000 2001 2002 2003 FACTORY SERVICE REPAIR MANUAL + WIRINGS

2000-2003 

Model: KTM 250, 400, 450, 520, 525, SX, MXC, EXC RACING

Loaded with Hi Resolution illustrations, instructions, photos, and diagrams, complete to service and repair your motorbike. 

TABLE OF CONTENTS:

1 SERVICE INFORMATIONS

2 GENERAL INFORMATION

3 REMOVING AND REFITTING ENGINE

4 DISASSEMBLING ENGINE

5 SERVICING INDIVIDUAL COMPONENTS

6 ASSEMBLING ENGINE

7 ELECTRICAL

8 FUEL SYSTEM

9 TECHNICAL SPECIFICATIONS

10 PERIODIC MAINTENANCE SCHEDULE

11 WIRING DIAGRAMS

MANUALS COVER:

OIL CIRCUIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2

ENGINE OIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

CHECKING THE ENGINE OIL LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

CHANGING THE ENGINE OIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

CHANGING THE OIL FILTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5

CHECKING THE OIL LEVEL OF THE HYDRAULIC CLUTCH . . . . . . . . . . . .2-6

BLEEDING OF THE HYDRAULIC CLUTCH . . . . . . . . . . . . . . . . . . . . . . . . .2-6

SPECIAL TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-7

CLEANING, STORAGE OF MOTORBIKE . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

DISMOUNTING THE ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2

MOUNTING THE ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

BLEEDING THE COOLING SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

CHECKING THE ADJUSTMENT OF THE HAND DECOMPRESSION

RELEASE CABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

ADJUSTING THE THROTTLE CABLES . . . . . . . . . . . . . . . . . . . . . . . .3-5

DRAINING THE ENGINE OIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

DISMOUNTING THE OIL FILTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

DISMOUNTING THE CHAIN WHEEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

DISASSEMBLING THE CLUTCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3

DISMOUNTING THE IGNITION SYSTEM (400/520 MODELS UNTIL 2002) . .4-3

DISMOUNTING THE IGNITION SYSTEM AND LOOSENING THE PRIMARY

GEAR (250 EXC MODELS FROM 2002, 450/525 MODELS FROM 2003) . .4-4

REMOVING THE FLYWHEEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

REMOVING THE CLUTCH DRIVE AND THE OUTER CLUCH HUB . . . . . . .4-5

DISMOUNTING THE OIL PUMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6

DISMOUNTING THE UPPER CYLINDER HEAD PORTION . . . . . . . . . . . . . .4-7

DISMOUNTING CYLINDER HEAD, CYLINDER AND PISTON . . . . . . . . . . .4-7

DISMOUNTING THE TIMING CHAIN AND THE TIMING GEAR . . . . . . . . .4-9

DISMOUNTING THE E-STARTER DRIVE GEAR AND KICKSTARTER . . . . . .4-10

DISMOUNTING THE PRIMARY GEAR AND FREEWHEEL . . . . . . . . . . . . .4-11

DISMOUNTING THE SHIFT MECHANISM AND TRANSMISSION . . . . . . .4-12

DISMOUNTING THE BALANCER SHAFT AND CRANKSHAFT . . . . . . . . . .4-13

LEFT CASING HALF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-2

RIGHT CASING HALF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3

CLUTCH COVER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-5

CRANKSHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6

CRANKSHAFT WEBS – MEASURE OUTER DIMENSION . . . . . . . . . . . . . . .5-7

DRIVING GEAR OF BALANCER SHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7

COMPENSATING THE AXIAL CLEARANCE OF THE CRANKSHAFT . . . . . . .5-7

CYLINDER – NICASIL COATING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-8

MEASURING PISTON AND CYLINDER, PISTON FITTING CLEARANCE . . . .5-8

PISTON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-9

MEASURING PISTON RING END GAP . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-9

CHECKING THE OIL PUMPS FOR WEAR . . . . . . . . . . . . . . . . . . . . . . . . . .5-9

LUBRICATION SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-10

UPPER PORTION OF CYLINDER HEAD . . . . . . . . . . . . . . . . . . . . . . . . . .5-11

CYLINDER HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-12

CAMSHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-14

PREASSEMBLING THE CAMSHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-15

TIMING CHAIN TENSIONER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-16

TIMING TRAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-16

CHECKING THE CLUTCH FOR WEAR . . . . . . . . . . . . . . . . . . . . . . . . . . .5-17

CHECKING THE KICKSTARTER FOR WEAR . . . . . . . . . . . . . . . . . . . . . . .5-19

PREASSEMBLING THE KICKSTARTER SHAFT . . . . . . . . . . . . . . . . . . . . . .5-19

SHIFT MECHANISM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-21

PREASSEMBLING THE SHIFT SHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-21

ASSEMBLING THE MAIN SHAFT (4-SPEED) . . . . . . . . . . . . . . . . . . . . . . .5-22

ASSEMBLING THE MAIN SHAFT (6-SPEED) . . . . . . . . . . . . . . . . . . . . . . .5-23

ASSEMBLING THE COUNTERSHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-24

IGNITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-25

REPLACING THE STATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-25

E-STARTER DRIVE GEAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-26

CHECKING THE FREE WHEEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-27

REPLACING THE FREE WHEEL HUB . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-27

MOUNTING THE CRANKSHAFT AND BALANCER SHAFT . . . . . . . . . . . . .6-2

MOUNTING THE SHIFT MECHANSIM AND TRANSMISSION . . . . . . . . . . .6-2

ASSEMBLING THE ENGINE CASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-4

MOUNTING THE PRIMARY GEAR AND FREE WHEEL . . . . . . . . . . . . . . . .6-4

MOUNTING THE OIL PUMPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-5

MOUNTING THE SHIFT ARRESTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6

MOUNTING THE E-STARTER DRIVE GEAR AND KICKSTARTER . . . . . . . . .6-6

MOUNTING THE OUTER CLUTCH HUB AND THE DRIVER . . . . . . . . . . . .6-7

MOUNTING THE PRIMARY GEAR NUT (250 EXC AND ALL MOD. FROM 2003) . .6-8

MOUNTING THE TIMING GEAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-9

MOUNTING THE PISTON AND CYLINDER . . . . . . . . . . . . . . . . . . . . . . .6-10

MOUNTING THE CYLINDER HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

MOUNTING THE CYLINDER HEAD TOP PORTION . . . . . . . . . . . . . . . . .6-12

MOUNTING THE TIMING CHAIN TENSIONER . . . . . . . . . . . . . . . . . . . .6-13

ADJUSTING THE VALVE CLEARANCE . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

MOUNTING THE FLYWHEEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-14

MOUNTING THE PULSE GENERATOR AND THE IGNITION COVER . . . . .6-14

MOUNTING THE CLUTCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

MOUNTING THE OIL LINE AND THE ELECTRIC STARTER . . . . . . . . . . . .6-16

MOUNTING THE OIL FILTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-17

HOW TO FILL IN ENGINE OIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-17

LEAKAGE INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2

REMOVING THE BATTERY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2

CHARGING THE BATTERY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2

FILLING THE BATTERY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

CHECKING THE CAPACITOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

CHECKING THE VOLTAGE REGULATOR-RECTIFIER . . . . . . . . . . . . . . . . . .7-4

CHECKING THE CHARGING VOLTAGE . . . . . . . . . . . . . . . . . . . . . . . . . . .7-4

CDI UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5

CHECKING THE IGNITION COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5

TROUBLESHOOTING IN THE IGNITION SYSTEM . . . . . . . . . . . . . . . . . . .7-5

MAIN FUSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-6

CHECKING THE ELECTRIC STARTER MOTOR . . . . . . . . . . . . . . . . . . . . . .7-6

CHECKING THE STARTER RELAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-6

MEASUREMENTS WITH PEAK VOLTAGE ADAPTER

STATIC IGNITION VALUES 250-525 SX, MXC, EXC RACING . . . . . . . . . . .7-7

STATIC GENERATOR VALUES 250-525 SX, MXC, EXC RACING . . . . . . . . .7-9

DYNAMIC GENERATOR VALUES 250-525 SX, MXC, EXC RACING . . . . . .7-11

THROTTLE VALVE SENSOR

ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-18

CHECK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-19

DISMOUNTING AND INSTALLING THE CARBURETOR . . . . . . . . . . . .8-4

DISASSEMBLING THE CARBURETOR (KEIHIN FCR 35/39) . . . . . . . . .8-5

DISASSEMBLING THE CARBURETOR (KEIHIN FCR-MX 37/39/41) . . . .8-8

CHOKE SLIDE AND HOT START KNOB . . . . . . . . . . . . . . . . . . . . . .8-11

CHECKING THE ACCELERATOR PUMP . . . . . . . . . . . . . . . . . . . . . .8-11

CHECKING THE JET NEEDLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-11

CHECKING THE FLOAT NEEDLE VALVE . . . . . . . . . . . . . . . . . . . . . .8-11

CHECKING THE THROTTLE VALVE . . . . . . . . . . . . . . . . . . . . . . . . .8-11

ASSEMBLING THE CARBURETOR (KEIHIN FCR 35/39) . . . . . . . . . . .8-12

ASSEMBLING THE CARBURETOR (KEIHIN FCR-MX 37/39/41) . . . . .8-15

ADJUSTING THE POSITION OF THE THROTTLE VALVE SENSOR . . . .8-18

CHECKING THE THROTTLE VALVE SENSOR . . . . . . . . . . . . . . . . . . .8-19

DISMOUNTING AND INSTALLING THE THROTTLE VALVE SENSOR . .8-19

CARBURETOR ADJUSTING IDLING (KEIHIN FCR 35/39) . . . . . . . . . .8-20

CHECKING/ADJUSTING THE FLOAT HEIGHT . . . . . . . . . . . . . . . . . .8-20

CARBURETOR ADJUSTING IDLING (KEIHIN FCR-MX 37/39/41) . . . .8-21

CHECKING/ADJUSTING THE FLOAT HEIGHT . . . . . . . . . . . . . . . . . .8-21

MODEL 2000

TECHNICAL SPECIFICATIONS – ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . .9-2

BASIC CARBURETOR SETTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-2

TIGHTENING TORQUES – ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-3

ASSEMBLY CLEARANCE, WEAR LIMIT . . . . . . . . . . . . . . . . . . . . . . . . . . .9-4

TECHNICAL SPECIFICATIONS – CHASSIS . . . . . . . . . . . . . . . . . . . . . . . . . .9-5

STANDARD ADJUSTMENT – FORK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-5

STANDARD ADJUSTMENT – SHOCK ABSORBER . . . . . . . . . . . . . . . . . . . .9-5

TIGHTENING TORQUES – CHASSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-5

MODEL 2001

TECHNICAL SPECIFICATIONS – ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . .9-6

BASIC CARBURETOR SETTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-6

TECHNICAL SPECIFICATIONS – CHASSIS . . . . . . . . . . . . . . . . . . . . . . . . . .9-7

STANDARD ADJUSTMENT – FORK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-7

STANDARD ADJUSTMENT – SHOCK ABSORBER . . . . . . . . . . . . . . . . . . . .9-7

MODEL 2002

TECHNICAL SPECIFICATIONS – ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . .9-8

BASIC CARBURETOR SETTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-9

MOUNTING CLEARANCES, WEAR LIMITS FOR MODELS UP TO 2002 . .9-10

TECHNICAL SPECIFICATIONS – CHASSIS . . . . . . . . . . . . . . . . . . . . . . . . .9-11

STANDARD ADJUSTMENT – FORK . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-11

STANDARD ADJUSTMENT – SHOCK ABSORBER . . . . . . . . . . . . . . . . . . .9-11

MODEL 2003

TECHNICAL SPECIFICATIONS – ENGINE . . . . . . . . . . . . . . . . . . . . . . . . .9-12

BASIC CARBURETOR SETTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

TIGHTENING TORQUES – ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-14

MOUNTING CLEARANCES, WEAR LIMITS FOR MODELS FROM 2003 . .9-15

TECHNICAL SPECIFICATIONS – CHASSIS . . . . . . . . . . . . . . . . . . . . . . . . .9-16

STANDARD ADJUSTMENT FORK / SHOCK ABSORBER . . . . . . . . . . . . . .9-16

TIGHTENING TORQUES – CHASSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-16

MODEL 2000

PERIODIC MAINTENANCE SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . .10-2

MODEL 2001

PERIODIC MAINTENANCE SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . .10-4

MODEL 2002

PERIODIC MAINTENANCE SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . .10-6

MODEL 2003

PERIODIC MAINTENANCE SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . .10-8

MODEL 2000

WIRING DIAGRAM USA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-2

WIRING DIAGRAM EU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

MODEL 2001

WIRING DIAGRAM EU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-5

WIRING DIAGRAM USA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

MODEL 2002

WIRING DIAGRAM USA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-8

WIRING DIAGRAM EU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

MODEL 2003

WIRING DIAGRAM USA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

WIRING DIAGRAM EU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-13

This manual is the same as the manual used by workshops. Service Manual contains detailed instructions and step by step diagrams for all workshop procedures.

 Language: English 
Format: PDF – Indexed and Searchable

COMPATIBLE WITH ALL WINDOWS & MAC COMPUTERS 
(WINDOWS 11, WINDOWS 10, WINDOWS 8 ETC.) 

Windows/Mac/Tablet/Phone Friendly

• SX (Motocross): The most aggressive tune, with stiffer suspension, close-ratio gearboxes, and often a smaller, lighter exhaust.
• MXC (Cross-Country): A blend of SX and EXC features, with a wide-ratio gearbox and a larger fuel tank for endurance racing.
• EXC (Enduro): Equipped with a wide-ratio gearbox, a large-capacity fuel tank, and a quiet exhaust. It is set up for technical off-road trails and is street-legal in some regions. 

• 2000–2002: The 2000 model year was the first to introduce the RFS engine, with some receiving upgrades in subsequent years. In 2001, models began appearing with semi-clear fuel tanks.
• 2003: The 2003 model year was a significant update, as KTM addressed several known issues
  • The Keihin FCR carburetor was updated to a stronger version that was less prone to cracking.
  • The cam bolt issue, where the bolt could come loose and cause engine failure, was fixed with a stronger, welded-in design.
  • Suspension was upgraded with new WP 48 mm forks and a reinforced rear hub. 

• Engine overheating: Like many liquid-cooled off-road bikes, the RFS engine can be susceptible to overheating, especially in tight, slow-speed conditions. A larger radiator or improved cooling fan can help.
• Electrical issues: Given the bikes’ age, electrical components like stators and wiring harnesses can fail. Some owners have reported issues with the bike dying when it gets warm, which could be an electrical fault.
• Countershaft spline wear: The splines on the countershaft, where the front sprocket is mounted, are known to wear prematurely on some models, which can cause the sprocket to move and eventually damage the shaft.
• Suspension: Older WP forks, particularly the 43 mm forks on 2000–2002 models, were not highly regarded and may require a service or rebuild to perform adequately for today’s riders.
• Starting issues: Problems with starting, particularly on the 525 EXC, can sometimes be traced to a faulty automatic decompression mechanism. A valve adjustment is a common fix.
• Clutch slave cylinder: The clutch slave cylinder can leak or fail. Fortunately, many aftermarket replacement parts are available. 

• Check for engine updates: If buying a pre-2003 model, check if the carb and cam bolt issues were fixed.
• Service records are critical: Due to the high-performance nature of these bikes, regular maintenance is essential. Oil changes should be frequent, with intervals ranging from 15 to 30 hours, depending on riding style.
• Pre-purchase inspection: A thorough inspection by a mechanic familiar with RFS engines is highly recommended. Pay close attention to the countershaft splines, engine for unusual noises, and the overall condition of the chassis and suspension.
• Parts availability: While many common parts are still available, some specific components for older models may be harder to find. Be prepared to search online parts forums and marketplaces like eBay.