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Tested: 2020 KTM 125 SX

KTM 125 SX 87.8kg 32.6 Bhp

The 125 SX is the direct descendant of a very long line of eighth litre motocross race bikes from Mattighofen. The evolution and improvements have never stopped, unlike on the Japanese bikes. And like all the Austria  machines, it keeps the single top-tube steel frame,

WP XACT suspension package and an engine with legendary power. It puts almost 40bhp with a weight of just 87.8kg. The carburettor is a classic Mikuni TMX 38 with a flat slide. Fuel injection isn’t quite ready yet for 125 motocross bikes.

The WP XACT air fork work well, taking the sting off the arms. The bike really is very comfortable to ride. The rear WP XACT initially kicked a bit; as it did on the Husqvarna TC125. We dropped the sag from 98 to 103,mm which worked well. The bike pushed a lot less in the corners and was just more secure. But the rear loves to kick and skip around a little. We slowed both compression and rebound, which really improved the skittish feeling.


Motor oil: 0.8 litres
Oil change: after running in (5 hours) and then every 20 hours
Air filter cleaning: after every race, replaced when used in sand
Piston Replacement: every 20 hours
Valves: Check after the first 3 hours and then every 30 hours
Starter motor: N/A
Oil mix: 40:1
Front: Dunlop Geomax MX3SF 80 / 100-21
Rear: Dunlop Geomax MX3S 100 / 90-19

What the testers said:

Pablo d’Aniello:

The bike gives you a lot of confidence. I like the bodywork, too, which is easy to grip with your legs. The bottom end power is OK but it quickly becomes explosive. It has such as stong engine, even more aggressive than the TC right from low to high revs. And the suspension is good when you adjust it to your preference.

Edoardo Boga:

I liked it a lot. It has so much power and it’s stable on the fast parts. It really is the complete package. It has good ergonomics and the fit of the handlebar, seat and footpegs is spot on. I didn’t like the air fork too much, as I feel is which dives a lot and lacks sensitivity. But I did think the rear was excellent, giving lots of traction.