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2017 KTM 125 SX Overview
KTM 125 SX is a cross / motocross motorcycle, displacing 124.80 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 2017 125 SX tips the scales at 87.2 kg, carries a 7-litre fuel tank, offers a seat height of 960 mm and spans a 1,485 mm wheelbase. That's roughly 11.4 kg lighter than the average cross / motocross motorcycle in our database. The full 2017 KTM 125 SX spec sheet below covers every technical detail, from suspension travel to tyre sizes.
2017 125 SX - Pros & Cons
Strengths
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✓
Factory engineering: KTM built the 125 SX around a straightforward, purposeful specification rather than chasing any single standout feature.
Considerations
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🔧
Carburetor fuelling: Expect to spend more time keeping the carbs in tune, especially after long storage periods or a change in altitude.
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📏
Tall seat height: At 960 mm, shorter riders will likely be on tiptoes at a standstill - worth sitting on one before you buy.
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Modest fuel capacity: Range between stops is limited by the 7-litre tank - plan fuel stops accordingly on longer routes.
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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, ? 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
87.2 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 2017 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.
2017 KTM 125 SX - Frequently Asked Questions
What engine does the 2017 KTM 125 SX have?
The 2017 KTM 125 SX uses a Single cylinder, two-stroke engine with 124.80 cc of displacement.
How much does the 2017 KTM 125 SX weigh?
The 2017 KTM 125 SX weighs 87.2 kg. This is the manufacturer's dry figure.
What is the fuel tank capacity of the 2017 KTM 125 SX?
The 2017 KTM 125 SX has a 7-litre fuel tank. At around 5-6 litres per 100 km, that is roughly 116-140 km between stops.
Is the 2017 KTM 125 SX suitable for shorter riders?
The 2017 KTM 125 SX has a seat height of 960 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 2017 KTM 125 SX have?
The 2017 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 2017 KTM 125 SX use?
The 2017 KTM 125 SX uses Carburettor. Mikuni TMX, providing precise fuelling across the rev range and reliable cold-start behaviour.
What suspension does the 2017 KTM 125 SX have?
The 2017 KTM 125 SX uses WP-USD, AER 48, ? 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 |
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- |
- |
- |
- |
- |
- |
- |
- |
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
87.2 kg / 192.2 lbs
Fuel Capacity
7.00 litres / 1.85 gallons
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Full 2017 KTM 125 SX Specifications
Colours
Orange/white/black
Ground Clearance (in.)
14.8 inches
Ground Clearance (mm)
375 mm
Seat Height
960 mm / 37.8 in.
Wheelbase
1,485 mm / 58.5 in.
Dry Weight
87.2 kg / 192.2 lbs
Fuel Capacity
7.00 litres / 1.85 gallons
Bore x Stroke (in,)
2.1 x 2.1 inches
Bore x Stroke (mm)
54.0 x 54.5 mm
Displacement (cc)
124.80 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
Multi-plate clutch, Brembo hydraulics
Final Drive
Chain
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, ? 48 mm
Suspension - Rear
WP shock absorber with linkage
Rake
26.5°
Wheel Travel - Front
300 mm / 11.8 in.
Wheel Travel - Rear
300 mm / 11.8 in.
Brakes - Front Diameter (in.)
10.2 inches
Brakes - Front Diameter (mm)
260 mm
Brakes - Rear Diameter (in.)
8.7 inches
Brakes - Rear Diameter (mm)
220 mm
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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