Contents

1 MEANS OF REPRESENTATION
- 1.1 Symbols used
- 1.2 Formats used
2 SAFETY ADVICE
- 2.1 Use definition intended use
- 2.2 Misuse
- 2.3 Safety advice
- 2.4 Degrees of risk and symbols
- 2.5 Tampering warning
- 2.6 Safe operation
- 2.7 Protective clothing
- 2.8 Work rules
- 2.9 Environment
- 2.10 Owner's Manual
3 IMPORTANT NOTES
- 3.1 Manufacturer warranty, implied warranty
- 3.2 Fuel, auxiliary substances
- 3.3 Spare parts, accessories
- 3.4 Service
- 3.5 Figures
- 3.6 Customer service
4 VIEW OF VEHICLE
- 4.1 View of vehicle, front left (example)
- 4.2 View of vehicle, rear right (example)
5 SERIAL NUMBERS
- 5.1 Vehicle identification number
- 5.2 Type label
- 5.3 Engine number
- 5.4 Fork part number
- 5.5 Shock absorber article number
6 CONTROLS
- 6.1 Clutch lever
- 6.2 Hand brake lever
- 6.3 Throttle grip
- 6.4 Switch-off button
- 6.5 Start button (125 XC US)
- 6.6 Service hour counter
- 6.7 Opening the fuel tank filler cap
- 6.8 Closing the fuel tank filler cap
- 6.9 Fuel tap (All SX models)
- 6.10 Fuel tap (125 XC US)
- 6.11 Choke
- 6.12 Shift lever
- 6.13 Kick starter lever
- 6.14 Foot brake lever
- 6.15 Plug-in stand (All SX models)
- 6.16 Side stand (125 XC US)
7 PREPARING FOR USE
- 7.1 Advice on preparing for first use
- 7.2 Running in the engine
- 7.3 Starting power of lithium-ion batteries at low temperatures (125 XC US)
- 7.4 Preparing the vehicle for difficult operating conditions
- 7.5 Preparing the vehicle for riding on dry sand
- 7.6 Preparing the vehicle for riding on wet sand
- 7.7 Preparing the vehicle for riding on wet and muddy circuits
- 7.8 Preparing vehicle for high temperatures or slow riding
- 7.9 Preparing the vehicle for low temperatures or snow
8 RIDING INSTRUCTIONS
- 8.1 Checks and maintenance measures when preparing for use
- 8.2 Starting
- 8.3 Starting off
- 8.4 Shifting, riding
- 8.5 Applying the brakes
- 8.6 Stopping, parking
- 8.7 Transporting
- 8.8 Refueling
9 SERVICE SCHEDULE
- 9.1 Additional information
- 9.2 Required work
- 9.3 Recommended work
10 TUNING THE CHASSIS
- 10.1 Checking the basic chassis setting with rider's weight
- 10.2 Air suspension XACT 5448
- 10.3 Compression damping of the shock absorber
- 10.4 Adjusting the low-speed compression damping of the shock absorber
- 10.5 Adjusting the high-speed compression damping of the shock absorber
- 10.6 Adjusting the rebound damping of the shock absorber
- 10.7 Measuring the rear wheel dimension unloaded
- 10.8 Checking the static sag of the shock absorber
- 10.9 Checking the riding sag of the shock absorber
- 10.10 Adjusting the spring preload of the shock absorber
- 10.11 Adjusting the riding sag
- 10.12 Checking the basic setting of the fork
- 10.13 Adjusting the fork air pressure
- 10.14 Adjusting the compression damping of the fork
- 10.15 Adjusting the rebound damping of the fork
- 10.16 Handlebar position
- 10.17 Adjusting the handlebar position
11 SERVICE WORK ON THE CHASSIS
- 11.1 Raising the motorcycle with a lift stand
- 11.2 Removing the motorcycle from the lift stand
- 11.3 Bleeding the fork legs
- 11.4 Cleaning the dust boots of the fork legs
- 11.5 Removing the fork legs
- 11.6 Installing the fork legs
- 11.7 Removing the fork protector
- 11.8 Installing the fork protector
- 11.9 Removing the lower triple clamp
- 11.10 Installing the lower triple clamp
- 11.11 Checking steering head bearing play
- 11.12 Adjusting steering head bearing play
- 11.13 Lubricating the steering head bearing
- 11.14 Removing the start number plate
- 11.15 Installing the start number plate
- 11.16 Removing front fender
- 11.17 Installing front fender
- 11.18 Removing the shock absorber
- 11.19 Installing the shock absorber
- 11.20 Removing the seat
- 11.21 Mounting the seat
- 11.22 Removing the air filter box cover
- 11.23 Installing the air filter box cover
- 11.24 Removing the air filter
- 11.25 Cleaning the air filter and air filter box
- 11.26 Installing the air filter
- 11.27 Preparing air filter box cover for securing
- 11.28 Removing the main silencer
- 11.29 Installing the main silencer
- 11.30 Changing the glass fiber yarn filling in the main silencer
- 11.31 Removing the fuel tank
- 11.32 Installing the fuel tank
- 11.33 Checking the chain for dirt
- 11.34 Cleaning the chain
- 11.35 Checking the chain tension
- 11.36 Adjusting the chain tension
- 11.37 Checking the chain, rear sprocket, engine sprocket, and chain guide
- 11.38 Checking the frame
- 11.39 Checking the link fork
- 11.40 Checking throttle cable routing
- 11.41 Checking the rubber grip
- 11.42 Adjusting the basic position of the clutch lever
- 11.43 Checking/correcting the fluid level of the hydraulic clutch
- 11.44 Changing the hydraulic clutch fluid
12 BRAKE SYSTEM
- 12.1 Checking the free travel of the hand 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
- 12.5 Adding front brake fluid
- 12.6 Checking the front brake linings
- 12.7 Changing the front brake linings
- 12.8 Checking the free travel of foot brake lever
- 12.9 Adjusting the basic position of the foot brake lever
- 12.10 Checking the rear brake fluid level
- 12.11 Adding rear brake fluid
- 12.12 Checking the brake linings of the rear brake
- 12.13 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 tire pressure
- 13.7 Checking spoke tension
14 ELECTRICAL SYSTEM
- 14.1 Removing the 12-V battery (125 XC US)
- 14.2 Installing the 12 V battery (125 XC US)
- 14.3 Charging the 12-V battery (125 XC US)
- 14.4 Changing main fuse (125 XC US)
15 COOLING SYSTEM
- 15.1 Cooling system
- 15.2 Radiator cover
- 15.3 Installing the radiator cover
- 15.4 Removing the radiator cover
- 15.5 Checking the antifreeze and coolant level
- 15.6 Checking the coolant level
- 15.7 Draining the coolant
- 15.8 Refilling with coolant
- 15.9 Changing the coolant
16 TUNING THE ENGINE
- 16.1 Checking throttle cable play
- 16.2 Adjusting throttle cable play
- 16.3 Carburetor tuning
- 16.4 Carburetor idle setting
- 16.5 Carburetor - adjusting the idle speed
- 16.6 Plug-in connector of ignition timing map adjustment
- 16.7 Changing the ignition timing map
- 16.8 Checking the basic position of the shift lever
- 16.9 Adjusting the basic position of the shift lever
17 SERVICE WORK ON THE ENGINE
- 17.1 Emptying the carburetor float chamber
- 17.2 Checking the gear oil level
- 17.3 Changing the gear oil
- 17.4 Adding the gear oil
18 CLEANING, CARE
- 18.1 Cleaning the motorcycle
19 STORAGE
- 19.1 Storage
- 19.2 Preparing for use after storage
20 TROUBLESHOOTING
21 TECHNICAL DATA
- 21.1 Engine
  - 21.1.1 All 125 models
  - 21.1.2 150 SX
- 21.2 Engine tightening torques
- 21.3 Carburetor
  - 21.3.1 125 SX
  - 21.3.2 Carburetor tuning (125 SX)
  - 21.3.3 Carburetor - basic setting for sandy surfaces (All 125 models)
  - 21.3.4 150 SX
  - 21.3.5 Carburetor tuning (150 SX)
  - 21.3.6 Basic carburetor setting for sandy surfaces (150 SX)
  - 21.3.7 125 XC US
  - 21.3.8 Carburetor tuning (125 XC US)
  - 21.3.9 Carburetor - basic setting for sandy surfaces (All 125 models)
- 21.4 Capacities
  - 21.4.1 Gear oil
  - 21.4.2 Coolant
  - 21.4.3 Fuel
- 21.5 Chassis
- 21.6 Electrical system
- 21.7 Tires
- 21.8 Fork
  - 21.8.1 All SX models
  - 21.8.2 125 XC US
- 21.9 Shock absorber
  - 21.9.1 All SX models
  - 21.9.2 125 XC US
- 21.10 Chassis tightening torques
22 SUBSTANCES
23 AUXILIARY SUBSTANCES
24 STANDARDS
25 LIST OF ABBREVIATIONS
INDEX
- 1
- A
- B
- C
- D
- E
- F
- G
- H
- I
- K
- L
- M
- O
- P
- R
- S
- T
- V
- W

KTM SX 125 2021 Owner's Manual

Pages 152

Year 2021

Language(s)

of 152

KTM SX 125 2021 Motorcycle Specification

The KTM SX 125 2021 is a high-performance motocross motorcycle designed to deliver exceptional agility and power, catering to competitive riders and off-road enthusiasts alike. At its core, the bike features a 124.8cc single-cylinder, two-stroke engine, optimized for a perfect blend of power and lightweight handling. The engine incorporates advanced technologies such as a power valve system and a high-performance exhaust, ensuring responsive throttle control and robust acceleration. The KTM SX 125 is paired with a six-speed transmission that boasts precise gear shifts, enhancing its race-ready capabilities.

The chassis of the KTM SX 125 is constructed from lightweight chrome-molybdenum steel, providing an excellent balance of rigidity and flexibility. This contributes to superior handling and stability, even on rough terrain. The bike is equipped with WP XACT suspension components, including fully adjustable front forks and a rear shock absorber, allowing riders to fine-tune their setup for optimal performance and comfort.

Ergonomics are a focal point in the design, with a slim bodywork and a flat seat profile that enable easy movement and control. The bike's lightweight design, coupled with its narrow frame, ensures maximum maneuverability. High-quality Brembo brakes offer excellent stopping power, contributing to the bike’s overall safety and control.

The KTM SX 125 also features a high-capacity air filter system and a large-diameter exhaust pipe, enhancing its engine performance and durability. The bike comes standard with high-grip footpegs, a robust chain guide, and a durable plastic skid plate for added protection. Overall, the KTM SX 125 2021 stands out as a top-tier motocross machine, combining advanced engineering with rider-focused design to deliver a superior off-road experience.

KTM SX 125 2021 Motorcycle F.A.Q.

How often should I change the oil in my KTM SX 125 2021?

It's recommended to change the oil every 10 hours of riding or after every race to ensure optimal engine performance and longevity.

What type of fuel should be used for the KTM SX 125 2021?

Use high-octane unleaded fuel with a minimum of 95 RON to ensure proper engine performance and to prevent knocking.

How can I adjust the suspension on my KTM SX 125 2021 for better handling?

To adjust the suspension, refer to the owner’s manual for recommended settings based on your weight and riding style. You can adjust the front fork compression and rebound as well as the rear shock preload for optimal handling.

What is the correct tire pressure for the KTM SX 125 2021?

The recommended tire pressure is 12 psi for the front tire and 12 psi for the rear tire, but it can be adjusted slightly depending on track conditions and personal preference.

How do I clean the air filter on my KTM SX 125 2021?

Remove the air filter, wash it with a suitable filter cleaner, rinse with water, let it dry completely, and apply a light coat of air filter oil before reinstalling.

What should I do if my KTM SX 125 2021 won't start?

Check the fuel level, ensure the kill switch is in the run position, inspect the spark plug for fouling, and make sure the carburetor is clean and functioning properly.

How do I adjust the chain tension on my KTM SX 125 2021?

To adjust the chain tension, loosen the axle nut, then turn the chain adjusters on both sides evenly until the chain has 10-15mm of slack. Tighten the axle nut securely after adjustment.

How often should I replace the spark plug on my KTM SX 125 2021?

Replace the spark plug every 20 hours of riding or if you notice any performance issues such as misfiring or difficulty starting.

What type of coolant should I use for the KTM SX 125 2021?

Use a high-quality ethylene glycol-based coolant mixed with distilled water in a 1:1 ratio for optimal cooling performance.

How do I maintain the brakes on my KTM SX 125 2021?

Regularly inspect the brake pads for wear, ensure the brake fluid is at the correct level and replace it every 2 years, and check for any leaks or damage to the brake lines.