TEN YEARS AGO TODAY: COMPLETE TEST OF THE 2013 KTM 350SXF—THE LITTLE BIKE THAT COULDN'T, BUT NOW IT CAN

Aug 11, 2023

This is an archived MXA test of the 2013 KTM 350SXF from the September 2013 issue of Motocross Action Magazine. Get your MXA subscription today.

Q: FIRST AND FOREMOST, IS THE 2013 KTM 350SXF BETTER THAN THE 2011 AND 2012 350SXF?

A: Awesomely so!

Q: HOW DOES THE 2013 KTM 350SXF COMPARE TO THE PREVIOUS TWO KTM?350SXF EDITIONS?

A: We have always been of the opinion that KTM had been sandbagging on the first generation of the 350SXF. The first edition in 2011 was overly rich and not especially fast. Making matters worse was a top-end-only powerband that pumped out a meager 46.94 horsepower at a skyscraper 12,200 rpm. Consumers expected a mid-size 450, but instead got a big 250. Not a single MXA test rider wanted to wait until 12,200 rpm to get an Open-class bike going?especially when their competition was at full tilt by 8500 rpm. We don't know about your riding style, but we don't have the patience to wait for the 350cc engine to lollygag its way up to the upper reaches of the rpm curve.

We didn't like the 2011 KTM 350SXF and said, "It's good and it's bad. It's focused and it's confused. It is, as you would expect from a machine that is trying to meld two worlds, a confused powerband. It is very much a Dr. Jekyll and Mr. Hyde engine (or maybe two Dr. Jekylls without a Mr. Hyde)."

Q: WASN’T THE 2012 KTM 350SXF A LOT BETTER THAN THE 2011 MODEL?

A: Yes, it was. When KTM introduced the 350SXF in 2011, they thought it best to set the fuel and ignition mapping to the mellow side of the scale. They knew this would cost some power, but they were hedging against catastrophe. In other words, they purposely made it slow to avoid the embarrassment of blown engines.

The 2012 KTM 350SXF was significantly faster and more responsive than the 2011 model because KTM took out their fail-safe mapping and made the 2012 engine 3 percent leaner from low-to-mid and 2 percent leaner from mid-to-top. The ignition timing was also advanced (approximately 2 degrees). With a solid two-horsepower gain from 9000 rpm to 12,000 rpm, the 2012 KTM 350SXF was quicker, snappier, faster and more responsive than the 2011 model. And that extra horsepower made the midrange more usable, even though peak still remained at 12,200 rpm. With more midrange horsepower, the 2012 KTM 350SXF gearbox was able to pull the gearbox gaps, with the aid of an extra tooth on the rear sprocket (we ran two teeth more in 2011).

Q: IS THE 2013 KTM 350SXF A NIGHT-AND-DAY IMPROVEMENT?

A: Yes. In fact, if the original 2011 KTM 350SXF had run as well as the 2013 350SXF, there would be a lot more 350cc bikes on the racetracks today (instead of in the hands of professional practice riders). The first year of the KTM 350SXF damped the enthusiasm of racers for the 350cc concept. Luckily for KTM, trail riders, play riders and professional practice riders embraced it and the sales figures were very good in 2011.

The gas tank is designed to allow free flow of air through the radiators and by the tank without blocking the flow.

Q: HOW DOES THE 2013 KTM 350SXF DIFFER FROM THE 2012 350SXF?

A: The MXA test crew was surprised by how many changes KTM made to the 2013 bike. After all, it was brand new in 2011. Here is the list of significant changes.

(1) Chassis. The chromoly steel frame gets a reinforced head tube, thinner wall-thickness tubes on the frame cradle, a beefed-up swingarm, a 25mm rear axle, lighter linkage bolts, redesigned head stays and all-new, all-orange bodywork.

(2) Suspension. The 48mm WP forks get the latest-generation red SKF fork seals and increased compression and rebound damping. Additionally, the 80-gram-lighter triple clamps have the bottom pinch bolts moved from fore/aft to left/right.

(3) Accoutrements. The wheels are equipped with black-anodized spokes, and the rear wheel has new spacers, a brake carrier and axle blocks to accommodate the 25mm axle (it was 20mm in 2012). Last year's low handlebar bend has been replaced by 12mm-taller Renthal 827 bars. A newly designed airbox is larger and has a new velocity stack. The WP radiators are made from a new alloy for increased structural strength.

In a paradoxical way, KTM pioneered the 350cc movement and hampered it at the same time. Now, in its third year of R&D, the KTM 350SXF is finally showing the promise of the mid-size concept.

Q: WHAT’S NEW INSIDE THE 2013 KTM 350SXF ENGINE?

A: Virtually everything. Although the cases may look the same, they are manufactured using high-pressure die-casting for a thinner wall thickness (and a 1-pound weight savings). The piston is a bridge-boxed Konig unit that runs on a Pankl rod with a pressure-lubricated plain bearing on the big end (as opposed to a roller bearing). The valves, piston, rod and plain bearing are rated at a maximum of 13,400 rpm. The kickstarter bosses have been removed from the cases to save weight, and the complete water jacket has been improved. The cylinder head has been massively reworked, with all new intake and exhaust ports and stiffer valve springs, plus new retainers and seats.

The fuel-injection throttle body has been upsized from 42mm to 44mm, with a new nozzle position in the bottom of the throttle body's venturi. Additionally, KTM did due diligence on the TPS (Throttle Position Sensor) by waterproofing it better, increasing the length of the lead-in wire and moving the idle adjuster to the back of the throttle body.

Q: HOW DOES IT RUN ON THE DYNO?

A: MXA's 2011 KTM 350 made 46.94 horsepower. The 2012 KTM 350SXF made 48 horsepower. The 2013 KTM 350SXF makes 54.18 horsepower. You read that right.

Q: HOW GOOD IS THE 2013 KTM 350SXF’S POWERBAND?

A: First of all, 54 horsepower is almost too good to be true?but it is true. However, there is a catch. At 54.18 horsepower, the 350SXF is actually more powerful than the 2013 Honda CRF450 (by over two horsepower) and about 2.75 horses shy of the 56.94 horsepower of the class leading KTM 450SXF. Believe it or not, KTM found a bundle of ponies in one model year with the 350SXF, which only confirms how much they had been sandbagging over the last two years. It should be noted that they weren't sandbagging to cheat, but to avoid mechanical failure.

We forgive you if you think that those dyno numbers mean that the 350SXF is as powerful as the 450, but flush that thought from your mind. The only place the KTM 350SXF makes more power than the 450 is after the 450 signs off.

The 2013 KTM 350SXF engine makes seven horsepower more than it did when it was first introduced in 2011. The MXA test crew still wishes it ran more like a mid-sized 450 than an over-sized 250, but it is vastly improved.

Q: HOW DOES THE 2013 KTM 350SXF’S POWERBAND COMPARE TO THE 2013 KTM 3450SXF’S POWERBAND?

Here is a quick horsepower rundown of the two machines.

(1) At 6000 rpm, the 450SXF makes seven horsepower more.(2) At 7000 rpm, the 450SXF makes eight horsepower more.(3) At 8000 rpm, the 450SXF makes eight horsepower more.(4) At 9000 rpm, the 450SXF makes five and a half horsepower more.

(5) At 10,000 rpm, the 450SXF makes three horsepower more.

(6) And finally, at 11,000 rpm, the KTM 350SXF catches the 450 in the horsepower race and beats it the rest of the way to the rev limiter, which is set about 2000 rpm higher on the 350 than on the 450.

For clarification, peak horsepower on the KTM 450SXF is at 9400 rpm, while the 350SXF makes peak power at 10,800 rpm. Although 10,800 is very high for peak power on an Open class race machines, it is much more usable than the previous 12,200 rpm of the 350SXF.

Q: WHAT IS THE MOST IMPORTANT KTM 350SXF MOD THAT AN OWNER SHOULD DO?

A: Gear it down one tooth on the rear (from a 50-tooth sprocket to a 51-tooth sprocket) to get it to third gear sooner. It amps up the drive out of corners.

Q: HOW GOOD WAS THE SUSPENSION?

A: It was noticeably better than last year, but really not as good as what the majority of the competition offers.

Forks: Although the spring rates stayed the same in the 48mm WP forks, the damping was increased to help keep the forks higher in their stroke. We liked this, but the forks are still very busy in consecutive bumps. Last year the forks were very quick through the midstroke and danced around instead of absorbing energy, this year they do a better job…but not a great job. The key to success with the 2013 forks is careful selection of the compression clickers and a fail-safe bailout on the oil height (if you are lighter than 175 pounds).

Shock: KTM thinks that the 2013 350SXF is headed for the starting line under the guidance of a young and aggressive riders, but most likely it will be embraced by Vet racers and play rider, so the stock spring rate works for riders from 175 pounds to 210 pounds. If you are lighter than that, KTM has a 5.4 kg/mm spring in the parts room.

Q: HOW DOES IT HANDLE?

A: Awesome. It tracks like it's on rails. It is well balanced and stays level when other bikes are upset. It is the best all-around-handling bike on the track. We love the way the KTM 350SXF handles. This isn't a quick turning bike like the RM-Z450 or the 2013 CRF450, but not every bike should aspire to be on the razor's edge. It is an all-around handling that turns accurately, but still has straight-line stability. Once the chassis is balanced out?the KTM has the best all-around handling frame.

Q: WHAT DID WE HATE?

A: The hate list:

(1) Shock preload ring. Hate it. Who would make a preload ring out of rubber?

(2) Gearing. No sweat. We gear every KTM down one or two teeth.

(3) Seat foam. Feels good for a couple rides, and then it starts to settle in.

(4) Weight. We expected the 2013 KTM 350SXF to be lighter. It wasn't. It hit MXA‘s trusty scales at 236 pounds. This bike would be a lot better at 230 pounds.

(5) Fender. Someone in KTM's engineering department is a fan of the Euler-Bernoulli I-beam theory. This 1750 theory was the cornerstone of engineering during the Second Industrial Revolution, and, as with all things structural, it could be applied to the design of a front fender. On the other hand, we don't know that an I-beam front fender is necessarily the best possible expression of the theories expressed by Euler and Bernoulli.

(6) Torx bolts. We all want to be unique, which accounts for the popularity of tattoos, soul patches and wool caps in the summer. However, MXA is not quite sure that we want the bolt choice on our racing bikes to be the equivalent of Elvis-style sideburns. Having Torx bolts for the sake of having them is an open invitation not to tighten them. Warning, check the sprocket bolts constantly.

(7) P hilosophy. If you are buying the 350SXF thinking that you will be getting a mellower version of a 450SXF, banish the thought. What you will be getting is a pumped-up version of the 250SXF. You gotta rev the 350SXF to go fast. No rev, no ponies. Lots of rev, lots of ponies.

Q: WHAT DID WE LIKE?

A: The like list:

(1) Exhaust pipe. Finally, we can remove a KTM exhaust pipe without having to pull the shock off. On a side note, there are two perf-core cones inside the 42mm muffler core; one facing forward and one facing backward. The cones restrict exhaust flow, thus lessening the exhaust note. The 450SXF has one forward-facing cone, and the 250SXF has a wire-screen restrictor. All the KTMs pass the two-meter-max sound test easily?in fact, the 350SXF blew a 112.8 dB reading (and 115 is the upper limit).

(2) Steel clutch basket. The 350SXF does not use the exotic diaphragm clutch that comes on the 250SX and 450SXF, but it does have a durable, strong and money-saving steel clutch basket, plus it is hydraulic.

(3) Handlebars. The Renthal 827 bars are 12mm taller than last year's bars, which were 12mm too low.

(4) Reprogram. The 350SXF has three ignition (not fuel) maps embedded into the black box, but you need an accessory switch to access them. We prefer the "aggressive" curve.

(5) Gas cap. Gone is the quarter-turn gas cap. Thanks for the threads.

(6) Brakes. 260mm of pucker power.

(7) Power. Night-and-day better than last year's and eons better than in 2011.

(8) Fender. Yes, it is over-engineered, but it is better than what KTM had before.

(9) Airbox. We wish the filter was easier to secure properly, but we love the no-tool aspect of the KTM airbox.

(10) Selection. New SKF?seals, firmer damping, higher oil height and lighter triple clamps pay off in forks that are high-tech in design, but average in performance.

Q: WHAT DO WE REALLY THINK?

A: KTM did irreparable harm to the 350cc mid-size concept with the bike they introduced in 2011. The Austrians took a promising idea and killed its momentum by building a bike that was poorly planned, ill-conceived and underdeveloped. At the time, the motocross market was open to a 350cc engine wedged into a 250 chassis. They envisioned a bike that was light and agile, but had a broad and usable mid-sized powerband. That didn't happen. Instead, they got a slow-revving, high-rpm, 250-ish powerband in a heavy, softly suspended chassis.

Flash-forward two years and the 350SXF is a lot closer to the vision that customers had back in 2011. There has always been a potential market for a mid-sized Open bike, because it suits the riding styles of many Vet and off-road riders. If we had our druthers, we’d like to see KTM up the displacement to 375cc or 380cc to try and get more torque and oomph lower in the rpm range. But, for now, the KTM 350SXF has found its niche and they are finally offering what they promised.

This is how we set up our KTM 350SXF for racing. We offer it as a guide to help you find your own sweet spot.

WP FORK SETTINGSLast year's forks were a hot mess. They lacked mid-speed damping in both directions. They moved too quickly, boinged around and tended to bottom if push came to shove. For 2013, KTM increased the midstroke damping and raised the oil height to get the forks closer to where a high-horsepower, Open-class race bike should be. The result is better front suspension, but not class leading or class contending suspension. It is more raceable and able to support the typical KTM buyer's weight than it was back in 2011. For hardcore racing, we recommend this fork setup on the 2013 KTM 350SXF (stock specs are in parentheses): Spring rate: 0.48 kg/mm Oil height: 390cc Compression: 15 clicks out Rebound: 15 clicks out Fork leg height: 5mm up Notes: Last year we raised the fork oil height by 10cc, but for 2013, KTM raised the oil height at the factory by 10cc. KTM's forks come with different oil heights for each model. The 125SX and 150SX have their oil set at 360cc, the 250SX has 380cc, and the four-strokes roll out of the factory with 390cc. Unless you are a bantamweight, we don't think you will find the WP forks to be too stiff. KTM increased the compression damping noticeably over 2012, but they could go firmer. If the forks feel harsh, don't be afraid to lower the oil height by 10cc.

It is no secret that KTM borrowed a page from Yamaha when they chose their rising rate leverage ratio. Now they need to borrow Yamaha's shock valving.

WP SHOCK SETTINGSThe rear suspension setup isn't all that different from 2012, but it does have a different feel because of increased rigidity in the rear end. The rear axle is 5mm larger and the one-piece swingarm is beefier. The result is a better-tracking rear end,with less tendency to kick or yaw in the rough. For hardcore racing, we recommend this shock setup for the 2013 KTM 350SXF (stock specs are in parentheses): Spring rate: 5.7 kg/mm Race sag: 105mm Hi-compression: 2 turns out Lo-compression: 15 clicks out Rebound: 15 clicks out Notes: We don't think that the average 350SXF rider will need a stiffer shock spring?unless he is over 200 pounds. Smaller riders (those under 150 pounds) might opt to return to last year's softer 5.4 kg/mm rear spring.

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