How Do The 2019 KTM 350 SX-F's Engine & Chassis Changes Feel On The Track?
The KTM 350 SX-F is a unique motorcycle that should really be a lot more popular than it is. Perhaps it’s because no one currently pilots one at the highest levels of racing, or maybe it’s because its odd engine size makes it too powerful to race in the 250 class, but – in perception – not powerful enough to race against full-sized 450s. We’ve always been quite fond of the mid-sized bike because of its fun factor: it’s easy to throw around and scream like a little bike, and not quite as intimidating as a massive 450. It has certainly been competitive enough at the local level against larger machines – we’ve snared many a holeshot aboard past 350 SX-Fs – and its easier-to-control character oftentimes makes it a better choice in exceptionally slippery or technical conditions.
For 2019, KTM threw the Factory Edition playbook at the 350, as it now enjoys all of the same updates that the 2018 Factory Edition 450 SX-F did, and more. We took delivery of the 2019 350 SX-F today at Chaney Ranch and spent plenty of time aboard the bike. Were we impressed? Read on!
For 2019 the 350 SX-F engine has updates to the valve timing, exhaust system, airbox, airbox velocity stack and 44 mm Keihin throttle body. The cylinder head and exhaust camshaft have been lightened up, and thanks to KTM's new Moto GP endeavors, advancements in ECU technology and development have made their way onto the motocross bike lineup, and the dual-map system is designed to provide greater response and a lighter feel. Traction control is still an option in both map settings. The entire KTM line is now equipped with the diaphragm steel clutch system that last year's 450 SX-F debuted. A new, more-powerful lithium-ion battery powers the electric starter, making for quicker, more positive fire ups. The five-speed gearbox is now made by Pankl.
To the untrained eye, the frame itself looks identical save for new black paint, but reworked mounts, cross members and tubing result in a chassis that has more torsional rigidity for greater steering precision and bump absorption. Adding to the more-precise front end is a new triple clamp that is beefier in the front sections for added rigidity and control. Out back, the aluminum subframe is 40 mm longer, and the swingarm's range of adjustment was lengthened by 5 mm, giving you the ability to stretch out the bike's wheelbase with more-rearward wheel positioning.
Both ends of the WP suspension receive updates internal settings for improved comfort and control, though no major revisions were required by the new chassis as the bike's dimensions and leverage points remain the same. The left fork, which controls the air spring, received a spacer in the negative air chamber that reduces volume by 50% for more responsive action in the initial parts of the stroke. A more-rigid top triple clamp improves cornering precision and the feel of the front suspension. At the rear of the bike, a new main piston and revised valve settings in the shock are tuned to complement the front end and maintain excellent balance.
Of course, the all-new bodywork gives the bike a subtle, but excellent facelift. New plastics are narrower between the rider's legs, and a longer seat offers more room for maneuvering in comfort. The seat cover features modest silicone ribs for improved traction under acceleration.
On The Track
Ergonomically the new bodywork of the 2019 bike is noticeably slimmer and easier to maneuver on, and all testers agree that the bike is more comfortable with a lighter feel. The bike feels much narrower, and especially so at the radiators' widest point, right between your knees while seated. As soon as we took to the track aboard the 350 SX-F, it was apparent that the engine was quicker and freer-revving, which gives the bike a lighter feeling while riding. KTMs traditionally get quicker as they break in, with the sweet spot being around six to eight hours in the past. Right off the showroom floor, the 2019 350 SX-F exhibits a snappy, well-broken-in feel, and the bike no longer has that tight, restrictive feeling when new. The powerband of the new 350 SX-F is broader than one might expect from an engine of this size, and we have found that it can be ridden effectively around most tracks in third gear with a little clutch work. Of course, the 350 works best when revved aggressively like a smaller bike, but it is more at home being chugged than you might expect. One of our testers felt that he was in between gears so we added a tooth to the rear sprocket. This allowed him to grab third gear sooner while at the same time keeping the bike purring along in the upper ROM range. The new Pankl transmission has a buttery feel and has a shining reputation, as previously the Pankl transmission was sold as an aftermarket option in the Powerparts catalog. Clutch pull is lighter thanks to the new diaphragm spring, and the action of the clutch is flawless as usual.
The greater rigidity of new chassis allows the bike to steer with even greater precision, while maintaining a stable, yet lively feel at speed. As odd as it sounds, the livelier character of the engine gives the entire bike a lighter feel while riding; and this carries over into the bike's ability to change direction, respond to mid-air corrections, and inspire trust. The stiffer feel of the chassis is much appreciated in high-speed corners with something to glance off of, as the bike absorbs the impact and changes direction with precision, where the older chassis would sometimes flex and stand upright. Under braking, the bike has a much more positive feel and stays planted to the ground.
Suspension-wise, the KTM 350 SX-F is well balanced and easy to dial in. As we've said before, the WP AER48 is the best performing air fork; but now it is the only air fork still in production, as all four of the Japanese manufacturers have returned to the superior mechanical spring design. Still, the AER48 fork can be tuned to suit a wide range of riders with the simple addition or subtraction of air, and its performance on the track is far above the old air forks from Showa and Kayaba. Suspension action on both ends is supple in small braking and acceleration chop, but the fork lacks some control as it travels through the middle of its stroke before growing progressively firm at the end. The shock, meanwhile, is superb and inspires confidence as it gobbles up imperfections in the track's surface and does a fine job of keeping the rear wheel on the ground and clawing for traction.
The 2019 KTM 350 SX-F is an incredible machine that deserves serious consideration from 450-class racers who are realiztic about their ability to take full advantage of all the power a modern 450 has to offer. The 350 SX-F does most things as well as a bigger bike, but more importantly…it does several things better.