The Orange Brigade continues to perfect its one-of-a-kind KTM 350 SX-F motocross bike. For 2013, this European-built motorcycle sports a number of technical updates including an upgraded chassis and engine for enriched handling and acceleration experience around the moto track.
Contrary to the Japanese brands, KTM continues to employ a steel-trellis main frame which provides favorable chassis flex characteristics. Updates for ’13 include a reinforced headstock and the engine cradle tubing is now fabricated from thinner material which nets slight weight reduction. Lastly, the frame is now painted silver instead of black.
New triple clamps hold the WP fork that houses custom spring rates (0.49 kg/mm), valving, and lighter weight fork oil engineered specifically for the demands of Southern California motocross tracks which can include big jumps, whoops and rough and choppy terrain. Above, a slightly taller Renthal 827 Fatbar handlebar was fitted (equivalent to a standard 996 bend) paired to tacky dual-compound grips.
The rear suspension is a mix of old and new. Although the shock body and spring (5.8 kg/mm) is the same it has updated valving and functions in a linkage with lighter fasteners. The aluminum swingarm was modified for enhanced rigidity and the rear axle and hub bushings are new, too, necessitating the use of a triangle stand with a larger diameter plug. The wheels continue to be sourced from Excel and are laced with black corrosion-resistant spokes to machined aluminum hubs. Each wheel is shod with commercially available Dunlop Geomax MX51 tires in sizes 80/100-21 front and 110/90-19 rear.
(Top) The body panels now come with the graphics inlayed into the plastic. The gas cap is also now a conventional screw-type as opposed to the previous tab-style quarter turn. (Center) The engine electronics were upgraded for ’13 including a larger throttle body and new RC8R-sourced injector. (Bottom) Although it looks the same, the engine wears new cases and a fresh cylinder head. The piston, connecting rod and crankshaft are new as well and based off the parts in the factory race team bikes.
More chassis upgrades come in the form of re-styled bodywork including a new front fender with a heavier duty and more angular design that helps prevent movement when it’s coated from the underneath with mud. The front number plate was also reshaped. Both radiator shrouds as well as the airbox covers are produced with the graphic imbedded into the plastic for superior wear resistance. Speaking of the radiators, it’s new also and fabricated with a stronger aluminum for enhanced durability in a crash or tipover.
The fuel tank continues to offer nearly a 2.0 gallon capacity and is compatible with the larger 2.51-gallon tanks that come standard on the XC off-road models. Lastly the fuel cap is now a conventional screw-on type compared to a tab-style quarter-turn.
When compared directly to the 450 Motocross class it’s no surprise that the 350’s smaller 349cc Single always felt a little down on power. So engineers worked feverishly to broaden the powerband and give it a little extra top-end oomph. The engine cases are now produced in a different manufacturing method which allows for lighter weight and more precise tolerances. It also eliminates the previously optional kickstart gear which means the bike is electric start only.
Inside there is a new forged piston, paired to a Pankl connecting rod sourced straight from Toni Caroili’s factory racebike. The crankshaft is also new and said to be more durable. Extra power was also obtained by modifying the intake and exhaust ports inside the cylinder head. Lastly some of the valvetrain components including the intake valve springs, washers and retainers were upgraded to allow the engine to spin another 1400 rpm higher boosting redline to 13400 revs. A different exhaust pipe was also fitted utilizing KTM’s Header Resonator System which improves power while adhering to noise level mandates.
The engine’s electronics also received some attention in the form of a larger diameter throttle body and new fuel-injector sourced from the RC8R superbike. The throttle position sensor was also made to be more durable and the idle adjustment and high idle, cold start functions are no longer on the same knob. Other improvements include more durable rubber fittings on electrical components for better resistance to normal wear and tear.
(Top) Steering is step-less and predicable but the SX-F doesn’t turn quite as sharply as some of the other bikes in its class. (Centers) The 350 SX-F’s ergonomics work great for riders that are taller than average.The 350 SX-F offers 250-like handling with top-end engine power similar to that of the 450 class. (Below) With its reduced engine reciprocating mass the 350 SX-F feels relatively light in the air and on the ground.
To find out how the orange machine performs we had planned on racing it during this summer’s Monster Energy Mammoth Motocross races high up the Sierra Nevada’s. Unfortunately a scheduling snafu foiled the plan, so as a backup, we competed at SoCal’s Glen Helen Raceway with REM Motocross followed up by a morning at Perris Raceway.
If you’ve just come off riding a Japanese motocrosser the KTM takes some time to get used to. True, it has made considerable strides in the American motocross scene in an effort to capture that “conventional” feel but it still has some unique traits.
Handling-wise the 350 is one of the most predicable steering bikes there is. It doesn’t steer as sharply as the yellow brand of motocrossers but it’s stable and never turns more or less than what the rider inputs through the controls. Another nice touch is the slim contour of the radiator shrouds and gas tank which allow the rider to get their body forward in a turn.
The riding position when seated or standing is proportioned well but the bike feels more stretched out from front-to-back; a good thing for average and above-sized riders. The seat has ideal grip and the contour of the seat make it easy to squeeze when motoring through bumps and obstacles. The dual-compound hand grips work well, too, offering good traction without causing your hands to go numb during motos.
Since its release in ’11, KTM has steadily made improvements in the suspension department. And the new machine has damping settings geared toward faster and/or heavier riders than ever before. Both the fork and shock present ample balance but it did take some seat time to figure out what clicker settings functioned best. Fortunately the suspension has a relatively wide range of adjustment for a stock MX’er.
Bottom-end engine power can best be described as mild but the engine does feel snappier and more responsive than before. This makes the engine get on the pipe more quickly if you’re lugging the engine for a few moments in too high of a gear. Mid-range power also comes online earlier, but for faster riders, the name of the game with the 350 is revs. You have to ride it more like a 250 opposed to a 450 four-stroke. Keep the engine zinging and its crazy how much power it produces. The best part is that it keeps on revving and revving and never feeling like it will sign-off. The five-speed transmission works without flaw but the final drive gearing (13/50) did feel tall, but that may be attributed to the KTM’s mellower bottom-end power.
(From full stiff)
Low-Speed Compression: 15
High-Speed Compression: 2 turns
KTM’s 350 SX-F continues to be a niche machine that fills an important role in the motocross world. It bridges the gap between the 250 and 450 motocross genres. But with its stronger engine performance and more aggressive suspension settings it is better equipped to run with the big dogs come this year’s 450 Shootout.