2020 KTM 125 SX Specifications

Name: 2020 KTM 125 SX
Brand: KTM

Enduro / Off-Road • Specs last verified 13 July 2026

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2020 KTM 125 SX Overview

KTM 125 SX is an enduro / off-road motorcycle, displacing 124.8 cc. Power comes from a Single cylinder, two-stroke engine running Double Overhead Cams/Twin Cam (DOHC) valve actuation. Bore and stroke come in at 54 x 54.5 mm. On the road, the 2020 125 SX tips the scales at 137 kg. That's roughly 61.8 kg lighter than the average enduro / off-road motorcycle in our database. The full 2020 KTM 125 SX spec sheet below covers every technical detail, from suspension travel to tyre sizes.

2020 125 SX - Pros & Cons

Strengths

Fuel injection: Fuel injection means consistent cold starts and clean throttle response without the fussiness of a carbureted setup.

Considerations

Chain final drive upkeep: Budget time for routine chain maintenance - it's cheap to replace but needs consistent attention to avoid premature sprocket wear.

Wear Points & Servicing Notes

Fuelling & injector care

The fuel injection on the 125 SX needs little beyond good fuel and periodic use of an injector-cleaner additive - no jetting or float-bowl maintenance to worry about.

Valve clearance checks

With Double Overhead Cams/Twin Cam (DOHC) valve gear, the 125 SX needs periodic clearance checks; caught early they're a cheap adjustment, left unchecked they accelerate valve seat wear.

Brake disc and pad wear

Braking up front comes from Single disc - solid stopping power, with disc and pad wear best checked on the same schedule as tyre changes.

Suspension condition on used examples

The 125 SX's suspension runs WP upside-down Ø 48 mm at the front. The rear uses WP Monoshock. Fork-seal condition and rear linkage play are the two things worth checking before buying used.

Final drive maintenance

The 125 SX uses chain final drive, which is cheap to replace but needs regular cleaning, lubrication and tension checks to get a full service life out of the sprockets.

Frame & chassis check

Built around a Central double-cradle, the 125 SX's chassis is straightforward to inspect: look for corrosion, cracks or repair welds around stress points like the head-stock and swingarm mounts.

Low-speed handling

137 kg keeps the 125 SX easy to move around in tight spaces, car parks and on the stand alike.

125 SX - Buying & Maintenance Guide

What to check before buying

Before handing over money for a used 2020 KTM 125 SX, cover the fundamentals: service book and oil change history, chain and sprocket wear, and any sign of oil weeping around the casings. Cold-starting it yourself tells you a lot - a healthy 125 SX should catch quickly and settle into a smooth idle.

Oil and filter changes

Nothing protects a 125 SX's engine like disciplined oil changes - stay on the manufacturer's schedule (roughly every 6,000 km or annually). Match the viscosity grade to what the owner's manual specifies, not what's cheapest.

Fuel system care

Fuel injection on the 125 SX needs little attention beyond decent fuel and an occasional system-cleaner additive. Anything left standing for three months or more should have its fuel drained and replaced before it varnishes the injectors.

Valve clearance service

Valve clearances are easy to overlook on a used 125 SX since a bike out of spec doesn't always feel obviously wrong - but the wear it causes is real. Ask the seller for documentation before assuming it's 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

Not published by manufacturer

Torque

Not published by manufacturer

Top Speed

Not published by manufacturer

Weight

137 kg / 302.0 lbs

Fuel Capacity

Not published by manufacturer

Full 2020 KTM 125 SX Specifications

Colours White, Orange

Dry Weight 137 kg / 302.0 lbs

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

Clutch Wet multi-disc clutch, mechanically actuated

Final Drive Chain (final drive)

Gearbox 6-speed

Primary Drive 5/8 x 1/4 (520) O Ring. Primary drive: 22:72.

Frame Type Central double-cradle

Suspension - Front WP upside-down Ø 48 mm

Suspension - Rear WP Monoshock

Wheel Travel - Rear 150 mm / 5.9 in.

Brakes - Front Single disc

Brakes - Rear Single disc

Tyres - Front 110-17

Specifications are compiled from manufacturer documentation and cross-referenced technical sources, and corrected on an ongoing basis. Spot an error? Let us know.