MotoSpecs

2020 KTM 125 SX Specifications

Enduro / Off-Road

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2020 KTM 125 SX Overview

The 2020 KTM 125 SX is an enduro / off-road motorcycle built around 124.8 cc of displacement. Under the tank sits a Single cylinder, two-stroke engine running Double Overhead Cams/Twin Cam (DOHC) valve actuation. The bore and stroke measures 54 x 54.5 mm. From a practical standpoint, the 2020 125 SX tips the scales at 137 kg. Scroll down for the complete 2020 KTM 125 SX spec sheet covering every technical detail from suspension travel to tyre sizes.

2020 125 SX - Pros & Cons

Strengths

  • Fuel injection: The fuel injection injection system delivers crisp throttle response and reliable cold starts regardless of altitude or temperature.

Considerations

  • Age-related wear: As with any used 125 SX, a thorough pre-purchase inspection covering consumables, service history and tyres is always recommended.

Owner Experiences & Common Issues

Throttle response and fuelling

The fuel injection on the 2020 KTM 125 SX is generally well-regarded. Some owners note a slight hesitation at small throttle openings when cold, which clears once the engine reaches operating temperature. A quick visual check of the injector connectors during routine servicing is good practice on higher-mileage examples.

Valve clearance checks

Double Overhead Cams/Twin Cam (DOHC) engines should have valve clearances checked at the manufacturer's specified interval. Owners report that clearances can tighten over time on higher-mileage bikes, leading to slight ticking from the top end. Catching it early keeps the job simple and avoids more costly remediation.

125 SX - Buying & Maintenance Guide

What to check before buying

When inspecting a used 2020 KTM 125 SX, start with the basics: check the service book for oil change frequency, inspect the chain and sprockets for wear, and look for oil seepage around the engine casings and rocker covers. A cold start test is invaluable - a well-maintained 125 SX should fire up cleanly and settle to a smooth idle within a few seconds.

Oil and filter changes

Regular oil changes are the single most important maintenance task on any 125 SX. Stick to the manufacturer's interval - typically every 6,000 km or once a year, whichever comes first. Always use the correct viscosity grade as specified in the owner's manual.

Fuel system care

The 125 SX's fuel injection system is durable but benefits from quality fuel and the occasional use of a fuel-system cleaner additive. If the bike has been stored for more than three months, drain and replace the fuel to prevent varnish deposits in the injectors.

Valve clearance service

Check that valve clearances have been adjusted at the correct intervals on any used 125 SX. This is a job many owners skip because the bike does not immediately feel wrong - but tight clearances accelerate valve seat wear. Ask for proof it has been done.

2020 KTM 125 SX - Frequently Asked Questions

What engine does the 2020 KTM 125 SX have?
The 2020 KTM 125 SX uses a Single cylinder, two-stroke engine with 124.8 cc of displacement.
How much does the 2020 KTM 125 SX weigh?
The 2020 KTM 125 SX weighs 137 kg. This is the manufacturer's dry figure.
What brakes does the 2020 KTM 125 SX have?
The 2020 KTM 125 SX uses Single disc at the front and Single disc at the rear.
What tyre sizes does the 2020 KTM 125 SX use?
The front tyre size on the 2020 KTM 125 SX is 110-17.
What fuel system does the 2020 KTM 125 SX use?
The 2020 KTM 125 SX uses Injection, providing precise fuelling across the rev range and reliable cold-start behaviour.
What suspension does the 2020 KTM 125 SX have?
The 2020 KTM 125 SX uses WP upside-down Ø 48 mm up front and WP Monoshock at the rear.
What frame does the 2020 KTM 125 SX use?
The 2020 KTM 125 SX is built around a Central double-cradle frame.

KTM 125 SX Spec Evolution

The KTM 125 SX was produced across 21 model years (2003-2023). The table below highlights the key specifications that changed across the production run - useful whether you are comparing years or tracking down a specific variant.

Specification 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023
Wet Weight - - - - - - - - 104.0 kg / 229.3 lbs 292.1 kg / 643.9 lbs - 112.0 kg / 246.9 lbs - - - - - - - - -
Dry Weight 93.6 kg / 206.4 lbs 93.6 kg / 206.4 lbs 92.4 kg / 203.7 lbs 92.4 kg / 203.7 lbs 92.4 kg / 203.7 lbs 90.8 kg / 200.2 lbs 90.8 kg / 200.2 lbs 90.8 kg / 200.2 lbs 88.8 kg / 195.8 lbs 91.6 kg / 201.9 lbs 90.8 kg / 200.2 lbs 90.8 kg / 200.2 lbs 90.8 kg / 200.2 lbs 87.8 kg / 193.6 lbs 87.2 kg / 192.2 lbs 87.2 kg / 192.2 lbs 87.5 kg / 192.9 lbs 137 kg / 302.0 lbs 87.5 kg / 192.9 lbs 87.5 kg / 192.9 lbs 92.4 kg / 203.7 lbs
Engine Detail - - - - - - - - - Reed intake and exhaust control Reed intake. Reed intake. Reed intake. Reed intake. Reed intake. Reed intake. Reed intake. - - - -
Engine Type Single cylinder Single cylinder Single cylinder Single cylinder Single cylinder Single cylinder Single cylinder Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke Single cylinder, two-stroke
Seat Height 925 mm / 36.4 in. 925 mm / 36.4 in. 925 mm / 36.4 in. 925 mm / 36.4 in. 925 mm / 36.4 in. 960 mm / 37.8 in. 985 mm / 38.8 in. 985 mm / 38.8 in. 992 mm / 39.1 in. 992 mm / 39.1 in. 992 mm / 39.1 in. 992 mm / 39.1 in. 992 mm / 39.1 in. 960 mm / 37.8 in. 960 mm / 37.8 in. 960 mm / 37.8 in. 950 mm / 37.4 in. - 850 mm / 33.5 in. 950 mm / 37.4 in. 958 mm / 37.7 in.
Fuel Capacity 7.50 litres / 1.98 gallons 7.50 litres / 1.98 gallons 7.50 litres / 1.98 gallons 7.50 litres / 1.98 gallons 7.50 litres / 1.98 gallons 7.50 litres / 1.98 gallons 8.00 litres / 2.11 gallons 8.00 litres / 2.11 gallons 7.50 litres / 1.98 gallons 7.50 litres / 1.98 gallons 7.50 litres / 1.98 gallons 7.50 litres / 1.98 gallons 7.50 litres / 1.98 gallons 7.00 litres / 1.85 gallons 7.00 litres / 1.85 gallons 7.00 litres / 1.85 gallons 7.50 litres / 1.98 US gallons - 7.50 litres / 1.98 US gallons 7.50 litres / 1.98 US gallons 7.20 litres / 1.90 US gallons
Stroke 2 2 2 2 2 2 2 - - - - - - - - - - - - - 2-stroke
Ground Clearance (mm) 390 mm 390 mm 390 mm 390 mm 390 mm 390 mm 390 mm 390 mm 385 mm 395 mm 395 mm 395 mm 395 mm 375 mm 375 mm 375 mm 375 mm - 375 mm 375 mm 359 mm

Key Specifications

Engine

Single cylinder, two-stroke

Power

N/A

Torque

N/A

Top Speed

N/A

Weight

137 kg / 302.0 lbs

Fuel Capacity

N/A

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Full 2020 KTM 125 SX Specifications

Colours White, Orange
Power-to-Weight Ratio 0.1095 HP/kg
Bore x Stroke (in,) 2.1 x 2.1 inches
Bore x Stroke (mm) 54.0 x 54.5 mm
Displacement (cc) 124.8 cc
Displacement (ci) 7.62 cubic inches
Engine Type Single cylinder, two-stroke
Fuel Control Double Overhead Cams/Twin Cam (DOHC)
Fuel System Injection
Engine Lubrication Wet sump
Ignition Contactless, controlled, fully electronic ignition system with digital ignition timing adjustment, type Kokusan
Starter Electric
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