KTM 125 SX User Manual

OWNER'S MANUAL 2016
125 SX
150 SX
250 SX
250 XC
300 XC
Art. no. 3213330en

KTM 125 SX Specifications

General

Engine Type	1-cylinder, 2-stroke engine
Displacement	124.8 cm³
Bore/Stroke	54 mm / 54.5 mm
Starter	Kickstarter
Transmission	6-speed
Rear Suspension	WP XACT shock absorber with linkage
Front Brake	Disc brake
Rear Brake	Disc brake
Ground Clearance	375 mm
Seat Height	950 mm
Cooling	Liquid cooled
Front Suspension	WP XACT USD, Ø 48 mm
Fuel System	Carburetor
Clutch	Wet multi-disc clutch
Frame	Central double-cradle type in chrome-molybdenum steel

Summary

2 Safety Advice

2.1 Use Definition - Intended Use

Defines intended use for SX and XC models, differentiating usage environments.

2.2 Safety Advice

General safety instructions and importance of warning labels on the vehicle.

2.3 Degrees of Risk and Symbols

Defines danger levels (Danger, Warning, Caution, Note) and associated symbols.

2.4 Tampering Warning

2.5 Safe Operation

Covers general safe operating practices, including impairment, poisoning, and burns.

2.6 Protective Clothing

Emphasizes the importance of wearing appropriate protective clothing for safety.

6 Controls

6.1 Clutch Lever

6.2 Hand Brake Lever

6.3 Throttle Grip

6.4 Kill Switch

Explains the kill switch function and its possible states for engine operation.

6.5 Electric Starter Button (All XC Models)

6.8 Fuel Tap (All SX Models)

6.9 Fuel Tap (All XC Models)

6.10 Choke

6.11 Shift Lever

6.13 Foot Brake Lever

7 Preparing for Use

7.1 Advice on First Use

Provides critical safety advice and pre-ride checks for new users.

7.2 Running in the Engine

Guides on engine break-in procedures to ensure optimal performance and longevity.

7.3 Preparing the Vehicle for Difficult Riding Conditions

8 Riding Instructions

8.1 Checks and Maintenance Work When Preparing for Use

Lists essential checks and maintenance before riding for operating safety.

8.2 Starting

Details the procedure for starting the engine, including safety warnings and cold engine considerations.

8.3 Starting Off

Explains the steps for moving off from a standstill, including clutch and throttle control.

8.4 Shifting, Riding

Covers gear shifting techniques, riding advice, and handling unusual noises.

8.5 Braking

Provides instructions and warnings related to braking, including adapting to conditions.

8.6 Stopping, Parking

Details procedures for safely stopping and parking the motorcycle, including warnings.

8.8 Refueling

Covers safe refueling practices, fuel types, and tank capacity information.

9 Service Schedule

9.1 All SX Models Service Schedule

Outlines periodic maintenance tasks for SX models based on operating hours/races.

9.2 All XC Models Service Schedule

Details periodic maintenance tasks for XC models based on operating hours/races.

10 Tuning the Chassis

10.1 Checking the Basic Chassis Setting with the Rider's Weight

Explains how to adjust chassis settings based on rider weight for optimal performance.

10.2 Air Suspension AER 48 (125/150 SX EU)

10.3 Compression Damping of the Shock Absorber

10.4 Adjusting the Low-Speed Compression Damping of the Shock Absorber

Details how to adjust the low-speed compression damping of the shock absorber.

10.5 Adjusting the High-Speed Compression Damping of the Shock Absorber

Provides instructions for adjusting the high-speed compression damping of the shock absorber.

10.6 Adjusting the Rebound Damping of the Shock Absorber

Explains the procedure for adjusting the rebound damping of the shock absorber.

10.7 Measuring the Rear Wheel Sag Unloaded

10.8 Checking the Static Sag of the Shock Absorber

10.9 Checking the Riding Sag of the Shock Absorber

Explains the process for checking the riding sag with the rider's weight.

10.10 Adjusting the Spring Preload of the Shock Absorber

Provides instructions for adjusting the spring preload on the rear shock absorber.

10.11 Adjusting the Riding Sag

Guides on how to adjust the riding sag of the shock absorber.

10.12 Checking the Basic Setting of the Fork

10.13 Adjusting the Fork Air Pressure (125/150 SX EU)

Details how to adjust the air pressure in the front fork for the 125/150 SX EU models.

10.14 Adjusting the Compression Damping of the Fork

Explains how to adjust the compression damping on the front fork for various models.

10.15 Adjusting the Rebound Damping of the Fork

Details how to adjust the rebound damping on the front fork for various models.

10.17 Adjusting the Handlebar Position

11 Service Work on the Chassis

11.3 Bleeding the Fork Legs

11.5 Removing the Fork Legs

11.6 Installing the Fork Legs

11.9 Removing the Lower Triple Clamp

11.10 Installing the Lower Triple Clamp

11.11 Checking the Play of the Steering Head Bearing

11.12 Adjusting the Steering Head Bearing Play

Details the procedure for adjusting the steering head bearing play.

11.18 Removing the Shock Absorber

11.19 Installing the Shock Absorber

11.24 Removing the Air Filter

11.25 Cleaning the Air Filter and Air Filter Box

11.26 Installing the Air Filter

11.29 Disassembling the Main Silencer

11.30 Installing the Main Silencer

11.32 Removing the Fuel Tank

11.33 Installing the Fuel Tank

11.35 Cleaning the Chain

11.36 Checking the Chain Tension

Guides on how to check and adjust the drive chain tension, with safety warnings.

11.37 Adjusting the Chain Tension

Provides instructions for adjusting the drive chain tension.

11.38 Checking the Chain, Rear Sprocket, Engine Sprocket, and Chain Guide

11.41 Checking the Routing of the Throttle Cable

11.44 Adjusting Basic Position of Clutch Lever

11.45 Checking/Correcting the Fluid Level of the Hydraulic Clutch

11.46 Changing the Hydraulic Clutch Fluid

12 Brake System

12.1 Checking the Free Travel of the Hand Brake Lever

Explains how to check the free travel of the front brake lever.

12.2 Adjusting the Basic Position of the Hand Brake Lever

12.3 Checking the Brake Discs

12.4 Checking the Front Brake Fluid Level

Explains how to check the front brake fluid level and warnings.

12.5 Adding Front Brake Fluid

Provides instructions for adding front brake fluid, including safety precautions.

12.6 Checking the Front Brake Linings

Guides on checking the front brake linings for wear and damage.

12.7 Changing the Front Brake Linings

Details the procedure for changing the front brake linings.

12.8 Checking the Free Travel of Foot Brake Lever

Explains how to check the free travel of the rear brake lever.

12.9 Adjusting the Basic Position of the Foot Brake Lever

12.10 Checking the Rear Brake Fluid Level

Explains how to check the rear brake fluid level and warnings.

12.11 Adding Rear Brake Fluid

Provides instructions for adding rear brake fluid, including safety precautions.

12.12 Checking the Rear Brake Linings

Guides on checking the rear brake linings for wear and damage.

12.13 Changing the Rear Brake Linings

Details the procedure for changing the rear brake linings.

13 Wheels, Tires

13.1 Removing the Front Wheel

13.2 Installing the Front Wheel

13.3 Removing the Rear Wheel

13.4 Installing the Rear Wheel

13.5 Checking the Tire Condition

13.6 Checking the Tire Air Pressure

Guides on checking and setting correct tire air pressure for optimal performance.

13.7 Checking the Spoke Tension

14 Electrical System

14.1 Removing the Battery (All XC Models)

14.2 Installing the Battery (All XC Models)

14.3 Recharging the Battery (All XC Models)

14.4 Change the Main Fuse (All XC Models)

Explains how to locate and change the main fuse, including safety precautions.

15 Cooling System

15.5 Checking the Antifreeze and Coolant Level

Guides on checking coolant level and antifreeze protection, with safety warnings.

15.6 Checking the Coolant Level

Explains how to check the coolant level in the radiator, with safety warnings.

15.7 Draining the Coolant

15.8 Refilling with Coolant

16 Tuning the Engine

16.1 Checking the Play in the Throttle Cable

16.2 Adjusting the Play in the Throttle Cable

Provides instructions for adjusting throttle cable play for optimal performance.

16.3 Carburetor – Idle

Explains the influence of idle settings on engine behavior and lists factory settings.

16.4 Carburetor – Adjusting the Idle Speed

Details how to adjust the engine idle speed using specific screws.

16.5 Ignition Curve Plug-in Connector

16.6 Changing the Ignition Timing Map

Explains how to switch between 'Soft' and 'Performance' ignition timing maps.

16.7 Checking the Basic Position of the Shift Lever

16.8 Adjusting the Basic Position of the Shift Lever

16.9 Engine Characteristic – Auxiliary Spring (All 250/300 Models)

16.10 Engine Characteristic – Setting the Auxiliary Spring (All 250/300 Models)

17 Service Work on the Engine

17.1 Emptying the Carburetor Float Chamber

17.2 Checking the Gear Oil Level

Explains how to check the engine gear oil level when the engine is cold.

17.3 Changing the Gear Oil

17.4 Draining the Gear Oil

17.5 Refilling with Gear Oil

Guides on refilling the engine with the correct gear oil, including capacity.

17.6 Adding Gear Oil

19 Storage

19.1 Storage

19.2 Preparing for Use After Storage

20 Troubleshooting

Engine Cannot Be Cranked

Lists possible causes and actions for when the engine won't crank.

Engine Turns But Does Not Start

Addresses issues when the engine cranks but fails to start.

Engine Has No Idle

Outlines causes and solutions for lack of proper engine idling.

Engine Does Not Speed Up

Provides troubleshooting steps for acceleration issues.

Engine Has Too Little Power

Identifies causes and fixes for reduced engine power.

Engine Stalls or Pops Into Carburetor

Addresses issues related to engine stalling or backfiring.

Engine Overheats

Lists causes and solutions for engine overheating problems.

White Smoke Emission (Steam in Exhaust Gas)

21 Technical Data

Engine Specifications

Engine Tightening Torques

Lists critical torque values for engine components to ensure proper assembly.

Carburetor Specifications and Tuning

Details carburetor settings and tuning charts for various conditions and models.

Capacities

Chassis Specifications

Fork Specifications

Provides detailed specifications for the front fork, including damping and air pressure.

Shock Absorber Specifications

Lists detailed specifications for the rear shock absorber, including damping and sag.

Chassis Tightening Torques

Lists critical torque values for chassis components to ensure proper assembly.

22 Substances

Brake Fluid DOT 4 / DOT 5.1

Coolant

Engine Oil (15W/50)

Engine Oil, 2-stroke

Fork Oil (SAE 4) (48601166S1)

Shock Absorber Fluid (SAE 2.5) (50180751S1)

Super Unleaded (95 Octane) Mixed with 2-stroke Engine Oil (1:60)

Super Unleaded (98 Octane) Mixed with 2-stroke Engine Oil (1:40)