MotoSpecs

2019 KTM 125 SX Specifications

Cross / motocross • Specs last verified 13 July 2026

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2019 KTM 125 SX Overview

KTM 125 SX is a cross / motocross motorcycle, displacing 124.8 cc. Power comes from a Single cylinder, two-stroke engine. Bore and stroke come in at 54 x 54.5 mm. On the road, the 2019 125 SX tips the scales at 87.5 kg, carries a 7.50-litre fuel tank, offers a seat height of 950 mm and spans a 1485 mm wheelbase. That's roughly 11.1 kg lighter than the average cross / motocross motorcycle in our database. The full 2019 KTM 125 SX spec sheet below covers every technical detail, from suspension travel to tyre sizes.

2019 125 SX - Pros & Cons

Strengths

  • Factory engineering: KTM built the 125 SX around a straightforward, purposeful specification rather than chasing any single standout feature.

Considerations

  • Carburetor fuelling: Expect to spend more time keeping the carbs in tune, especially after long storage periods or a change in altitude.
  • Tall seat height: At 950 mm, shorter riders will likely be on tiptoes at a standstill - worth sitting on one before you buy.
  • Modest fuel capacity: Range between stops is limited by the 7.50-litre tank - plan fuel stops accordingly on longer routes.
  • 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

Carburetor maintenance

Carburetors on the 125 SX need periodic attention - pilot jets and float needles are the first parts to gum up after the bike sits, and the first thing to check if idle or throttle response degrades.

Brake disc and pad wear

Braking up front comes from Single disc. Brake calipers on floating bearings - 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-USD, AER 48, Ø 48 mm at the front. The rear uses WP shock absorber with linkage. 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 Chrome-molybdenum steel central-tube frame, 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

87.5 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 2019 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.

Carburetor upkeep

Deposits in the carbs are the usual culprit behind poor running on a stored 125 SX - strip and clean the float bowls before the first start. Pilot jets clog first and get overlooked most, so make a point of checking them.

2019 KTM 125 SX - Frequently Asked Questions

What engine does the 2019 KTM 125 SX have?
The 2019 KTM 125 SX uses a Single cylinder, two-stroke engine with 124.8 cc of displacement.
How much does the 2019 KTM 125 SX weigh?
The 2019 KTM 125 SX weighs 87.5 kg. This is the manufacturer's dry figure.
What is the fuel tank capacity of the 2019 KTM 125 SX?
The 2019 KTM 125 SX has a 7.50-litre fuel tank. At around 5-6 litres per 100 km, that is roughly 125-150 km between stops.
Is the 2019 KTM 125 SX suitable for shorter riders?
The 2019 KTM 125 SX has a seat height of 950 mm. This is towards the tall end of the spectrum and will require most riders under 175 cm to tiptoe at stops.
What brakes does the 2019 KTM 125 SX have?
The 2019 KTM 125 SX uses Single disc. Brake calipers on floating bearings at the front and Single disc. Brake calipers on floating bearings at the rear.
What fuel system does the 2019 KTM 125 SX use?
The 2019 KTM 125 SX uses Carburettor. Mikuni TMX, providing precise fuelling across the rev range and reliable cold-start behaviour.
What suspension does the 2019 KTM 125 SX have?
The 2019 KTM 125 SX uses WP-USD, AER 48, Ø 48 mm up front and WP shock absorber with linkage at the rear.

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

87.5 kg / 192.9 lbs

Fuel Capacity

7.50 litres / 1.98 US gallons

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Full 2019 KTM 125 SX Specifications

Colours Orange/white/black
Ground Clearance (in.) 14.8 inches
Ground Clearance (mm) 375 mm
Seat Height 950 mm / 37.4 in.
Wheelbase 1485 mm / 58.5 in.
Dry Weight 87.5 kg / 192.9 lbs
Fuel Capacity 7.50 litres / 1.98 US gallons
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
Engine Detail Reed intake.
Fuel System Carburettor. Mikuni TMX
Ignition Kokusan EMS
Starter Kick
Clutch Wet multi-disc clutch, hydraulically actuated
Final Drive Chain   (final drive)
Gearbox 6-speed
Primary Drive 13:50. Primary drive: 23:73.
Frame Type Chrome-molybdenum steel central-tube frame
Suspension - Front WP-USD, AER 48, Ø 48 mm
Suspension - Rear WP shock absorber with linkage
Rake 26.1°
Wheel Travel - Front 310 mm / 12.2 in.
Wheel Travel - Rear 300 mm / 11.8 in.
Brakes - Front Single disc. Brake calipers on floating bearings
Brakes - Rear Single disc. Brake calipers on floating bearings
Rims CNC machined hubs. Excel rims. Wire spoked.

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

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