aluminum. No more! For 2013, the 250SXF gets high-pressure, die-cast engine cases, resulting in thinner walls, improved metal structure and higher strength. In addition, the 2013 cases have been streamlined by the removal of the kickstart castings and by borrowing the water pump, counterbalancer and timing-chain gear shaft from the “Ryan Dungey Replica.” This allows one shaft to do the job of three shafts. ( 3) Cylinder head. Using the 350SXF as a base for the new 250SXF engine, the 2013 cylinder head gets larger intake valves (30.9mm to 32.5mm) for a 14 percent increase in the valve area (made possible by the new 78mm bore). The Konig bridge-box piston is designed to produce less vibration at high rpm (important on the 2013 engine). ( 4) Crankshaft. With the rev limiter set at 14,000 rpm, a stock crankshaft has never faced the challenge that the 250SXF’s big end will in 2013. To ensure that it is up to the task, KTM commissioned Formula 1 supplier Pankl to build them a special lightweight connecting rod, and, as icing on the cake, they swapped out the old big-end bearing for a plain bearing (bushing) that doubles the maintenance interval. ( 5) Exhaust. The big news about the KTM 250SXF exhaust system is that it can be removed from the bike without having to take the shock off the bike (it pulls out of the front now). The head pipe is hydroformed (with water pressure) into a tapered shape. KTM has added a resonance chamber to go along with a tapered muffler core and a sound-reducing wire screen in the end cap. The sound screen looks like a spark arrestor, but doesn’t pass the USFS test. Given that we sound-tested the 2013 KTM 250SXF at 112. 8 dB ( 3 dB below the two-meter-max requirement), we removed the screen to avoid having it clog up with muffler-packing particles later. ( 6) Transmission. The 2013 KTM 250SXF gets a totally new six-speed gearbox, but the only gear that has a different ratio is second gear, which is taller and closer to third gear. However, the final drive is also lower at 13/50. It was 13/49 in 2012. Q: WHAT’S UP WITH EMS, TPS AND EFI? A: KTM calls their EFI system EMS for Engine Management System (every manufacturer has their own acronym for EFI). For 2013, KTM reconfigured their complete EFI system with a 2mm-larger throttle body venturi (44mm from 42mm). Uniquely, KTM moved the location of the spray nozzle from the top of the venturi to the bottom so that it sprays upwards into the air stream. KTM claims that this atomizes the fuel more thoroughly because the fuel velocity is greater at the bottom of the throttle-body orifice than at the top. It’s no secret that KTM had serious Throttle Position Sensor (TPS) issues in 2011—even though they used the same TPS as Kawasaki and Suzuki. The problem was
2013 KTM 250SXF: After we criticized
last year’s 250SXF, KTM went back to
the drawing board. We’re glad that they
did. The new bike is blessed with a
fire-breathing engine that produced
42. 89 horsepower on our dyno.