KTM revealed its 2013 motocross model lineup featuring a new 250 four-stroke engine and updates to the 350 powerplant.

The 2013 KTM 250 SX-F gets a new powerplant said to be lighter than the previous engine thanks to a new high-strength aluminum alloy. The new engine has a 78mm bore and a 52.3 mm stroke, compared to the previous model’s 76mm bore and 54.8mm stroke.

According to KTM, the forged piston is lighter in weight despite a larger diameter, allowing for higher engine speeds. To counter the increased vibrations from higher revs, the 250 SX-F engine receives a new laterally-positioned balancer shaft which also drives the timing chain and water pump.

The 2013 KTM 350 SX-F also receives some updates including a 500 g weight reduction from a new die-cast housing. Strengthened valve heads and valve seats and updated valve springs allowed for lightweight titanium valves at the new higher rev limit of 13,400 rpm. The production model also inherits a new crankshaft from the factory race machines, featuring a new plain bearing in the lower connecting rod eye. The stiffer crankshaft not only allows for the higher rev limit, it also has a higher service interval than the previous component.

The 450 is based on the 2012 special edition Ryan Dungey KTM 450 SX-F announced in January.

All SX-F models receive new frames and triple clamps to improve rigidity, as well as updated suspension settings and new graphics.

The two-stroke SX models all received updated suspension, black anodized Renthal fat bars and graphics.

[Source: KTM, photos by Barbanti A, Freeman G., Schedl R. and Mitterbauer H.]