| Model | KTM 250 SX |
| Year | 2010 |
| Category | Motocross |
| Engine Type | Liquid-cooled single-cylinder two-stroke with reed-valve induction and exhaust power valve |
| Weight | 95.4 kg dry, without fuel |
| Displacement | 249 cc |
| Bore x Stroke | 66.4 x 72.0 mm |
| Compression Ratio | |
| Fuel System | Keihin PWK 36 S AG flat-slide carburettor with reed-valve induction | Replacement Options |
| Ignition | Kokusan 2K-1 / 2K-2 digital CDI ignition |
| Spark Plug | NGK BR8ECM |
| Spark Plug Gap | 0.60 mm |
| Cooling System | Liquid cooling; 1.2 L coolant capacity |
| Starting System | Kick starter |
| Transmission | 5-speed constant-mesh, claw-shifted manual |
| Clutch | Wet multi-disc clutch, hydraulically operated |
| Final Drive | Chain |
| Overall Length | 2100 mm |
| Overall Width | 820 mm |
| Overall Height | 1250 mm |
| Wheelbase | 1475 mm |
| Ground Clearance | 385 mm |
| Seat Height | 985 mm |
| Fuel Capacity | 8.0 L |
| Frame | Central double-cradle 25CrMo4 chrome-molybdenum steel frame |
| Front Tyre | 80/100-21 51M | Tyre Size Guide |
| Rear Tyre | 110/90-19 62M | Tyre Size Guide |
| Front Suspension | WP 4860 MXMA CC 48 mm upside-down closed-cartridge fork | Fork Oil Levels |
| Front Suspension Travel | 300 mm |
| Rear Suspension | WP PDS monoshock with linkless Progressive Damping System |
| Rear Suspension Travel | 335 mm |
| Fork Oil | SAE 5 fork oil |
| Front Brake | 260 mm hydraulic single disc with two-piston caliper |
| Rear Brake | 220 mm hydraulic single disc |
| Front Wheel Size | 21 in |
| Rear Wheel Size | 19 in |
| Fuel Type | Premium unleaded petrol mixed with high-quality two-stroke oil |
| Premix Information | 1:40 fuel-to-oil ratio | Premix Calculator |
| Gearbox Oil | 0.70 L SAE 15W-50 engine oil suitable for wet-clutch motorcycle transmissions |
| Air Filter | Washable oiled foam element |
| Service Notes | Competition motorcycle requiring frequent air-filter servicing, gearbox-oil changes and regular inspection of the piston, rings, reed valve, exhaust power valve, spark plug, clutch, chain and suspension components. |
The 2010 KTM 250 SX was primarily a refinement of the existing platform rather than a major redesign. KTM retained the proven 249 cc engine, five-speed gearbox, chrome-molybdenum frame and linkless WP PDS rear suspension that had evolved through the previous several seasons. The emphasis for 2010 was on fine-tuning a motorcycle that had already become one of the strongest remaining 250 two-strokes in motocross.
The engine continued with its 66.4 x 72.0 mm bore and stroke, reed-valve intake and exhaust power-valve system. A Keihin PWK 36 mm carburettor supplied the mixture, while the hydraulic clutch and broad five-speed transmission helped make the 250 SX unusually versatile for such a powerful two-stroke. Owners maintaining an ageing original carburettor can compare replacement options through the MXOwners carburettor reference.
Suspension remained WP at both ends. The 48 mm closed-cartridge fork offered 300 mm of travel, while the linkless PDS rear shock provided 335 mm. Correct fork servicing and rear sag are particularly important on this generation, and the MXOwners fork oil reference is useful when checking oil and setup information.
At only 95.4 kg without fuel, the 2010 250 SX remained dramatically lighter than many contemporary four-strokes. Strong Brembo brakes, a 21-inch front and 19-inch rear wheel and a compact 8-litre tank completed a very focused race package. Accurate premix remained essential, and the MXOwners premix calculator can help prepare the specified 1:40 fuel mixture.
Historically, the 2010 model represents the mature version of KTM's late-2000s PDS two-stroke chassis. KTM was one of the few manufacturers still seriously developing a full-size 250 two-stroke at the time, and the 250 SX remained fast, simple and highly competitive. The following years would bring further chassis evolution, making the 2010 bike an interesting final refinement of this particular generation.