2010 KTM 125SX

2010 KTM 125 SX: Continued Refinement of the Lightweight Racer

The 2010 KTM 125 SX was primarily a refinement of the established 125 SX platform rather than a major redesign. KTM retained the compact 124.8 cc two-stroke engine, six-speed gearbox, chrome-molybdenum steel chassis and linkless WP PDS rear suspension that had evolved through the previous several model years. Development concentrated on detail improvements and setup rather than replacing the basic package.

The engine continued to use a 54.0 x 54.5 mm bore and stroke, reed-valve induction and KTM's exhaust power-valve system. A 39 mm Keihin PWK carburettor supplied the mixture, while the hydraulic clutch and six-speed transmission helped make the lightweight 125 particularly effective when ridden aggressively. Owners maintaining an original machine can compare worn or replacement carburettor components through the MXOwners carburettor reference.

WP suspension remained a major part of the KTM package. The 48 mm closed-cartridge fork provided 300 mm of travel, while the PDS rear shock delivered approximately 335 mm without a conventional linkage. Correct fork oil, spring setup and rear sag remain important on these bikes, and the MXOwners fork oil reference is useful when servicing the front suspension.

At around 91 kg without fuel, the 2010 125 SX remained exceptionally light. Its continued development was also historically important: while several manufacturers were reducing two-stroke motocross development, KTM kept improving the 125 SX as a genuine competition machine. Accurate premix remains essential for surviving race use, and the MXOwners premix calculator can help prepare the correct fuel mixture.