2011 KTM 350 SX-F Comparison

JC Hilderbrand | December 22, 2010

KTM is the first to produce a modern purpose-built 350cc four-stroke motocross bike. The DOHC single-cylinder engine is electric start just like the 450, but trades the carburetor for a Keihin fuel injection system with 42mm throttle body and uses an 88 x 57.5mm bore/stroke cylinder with 13.5:1 compression ratio. It also gets the same Chromoly steel chassis and WP suspension with rising-rate linkage.

From our riders’ varied notebook entries, it’s clear just how new the 350 concept is. Since this is the first bike to judge from, each rider has their own idea of what a 350 is supposed to feel like in comparison to a 450 (or 250F for that matter). For instance, some think the bottom-end torque is good for an engine this size, and others consider it underpowered. What is generally agreed on is that while the engine characteristic is unlike any of the big bikes, the high-revving powerplant is effective. Even though it doesn’t have the outright torque, the 350 doesn’t spin its rear wheel like the bigger bikes, meaning it drives forward as well or better. This is particularly noticeable in dry, slick conditions. Deep, loamy soil is obviously going to benefit the tractoring 450s, but acceleration testing shows the 350’s mild low end can actually make it a better starter.

2011 KTM 350 SX-F
The 350 SX-F is competitive at all levels of racing, but it definitely has it’s own character and is unlike the 450 class.

The 350 peaks out at 45.2 horsepower and 27.7 lb-ft of torque – well below the rest of the class. But, the power curve is even more linear and can carry its power output higher in the rev range where others start to taper. In the drag race down our 175-foot starting line, the 350 was behind a two-way tie for first place between the Kawasaki and Honda by only 0.02 seconds. During the third-gear roll-on it again trailed the smooth-running Honda in second. With its big brother and the mighty Kawasaki and Suzuki behind it, that’s a lot of muscle to be showing up. As far as shootout scoring goes, those categories, combined with being the second-lightest behind the Honda, gave the 350 valuable points.

Unfortunately, even though riders admit the effectiveness of the 350, there was just no way it is going to earn the top vote in the on-track evaluation. Is it impressive for a 350? Yes. Is it a 450? No.

Even though it uses lighter springs in the WP fork and shock (0.48 and 5.4 N/m vs. 0.50 and 5.7 N/m) many riders consider the suspension action very similar to the heavier-sprung 450 SX-F. The 350 enjoys a four-pound weight advantage but feels even lighter on the track. However, not all of our testers were happy with the WP components. Our first day of testing at Racetown 395 generated so many complaints about the soft sticks that we installed a set of 450-spec springs. After that the complaints quieted down.

2011 KTM 350 SX-F
The Honda is lighter, but the KTM has a unique feel that makes riding it so much fun.

The five-speed transmission doesn’t always shift well under a load, and we don’t like how soft the stock WP suspension is. Heavier springs help considerably and electric start, massively powerful Brembo brakes and light handling are all excellent features that keep the 350 right in the mix. KTM didn’t come running from the factory raving about world domination on the smaller SX-F, particularly in the 450 class. In fact it’s mostly been billed as a bike that’s fun to ride – even though it’s obvious that its elite factory motocross racers are encouraged to ride the smaller machine (and it seems to be working out fine so far). If Tony Cairoli’s MX1 World Motocross Championship wasn’t enough to convince you, our testing has proved it’s more than capable of being competitive. A fifth-place ranking is impressive considering the brute power this lightweight machine is stacked against.

2011 KTM 350 SX-F Rider Impressions:

2011 KTM 350 SX-F
The 350 has many similarities with the larger KTM.

Frankie Garcia – 5’8” – 165 lbs – Novice
The 350 engine really surprised me. Unlike the 450, the 350 had excellent bottom-end power. It revved really good and had power that seems to be closer to a 450 than a 250. The bike ran out very well against the bigger 450 machines until around fourth gear. After that the bike just didn’t have the top end it needed to hang. The transmission was a little on the tough side to shift under load, but the ratio of the gears was spot on. As for the rest of the bike, the clutch, brakes, ergonomics and even the suspension and handling all felt very similar to the 450 SX-F.

Kyle Lewis – 5’10” – 180 lbs – Vet Expert
Where do I start with this one? Not too much bottom compared to the 450’s. Good over-rev, but it needs it. Not too much torque. Pretty smooth. This bike is hard to explain. The roll-on power is not very strong and I have to keep it revved up which is hard because I feel like I’m between gears while cornering. In particular, second feels too low and third is too high.

The transmission action felt the same as the 450, but I just never felt like I was in the right gear. This bike feels lighter than the 450, but it still has a heavy feel. I also detect the chassis flexing similar to the 450, but with a touch more stability, possibly due to the lower torque/motor inertia. I’m not sure this bike should be tested against the 450s. Good concept, but not a 450. Sorry, KTM.

Bret Milan – 6’4” – 210 lbs – Intermediate
This is an incredibly fun bike to ride. Big-bore 250Fs usually gain torque but not much up top. This purpose-built 350 powerplant is a screamer with very competitive top-end power. You have to keep it “on the pipe” to make competitive power, though, and with my size and riding skills, I don’t feel that I could be competitive racing this bike against 450s. 

2011 KTM 350 SX-F
2011 KTM 350 SX-F
With less rotating mass in the engine, the 350 SX-F corners and flies extremely well.

The suspension was well balanced although a bit soft for me. The smooth power really made the bike hook up well. The 350 is very light, nimble and flickable. The friendly power deliver and light feeling of the crank and flywheel really work to make this bike easy to ride. Stability was excellent as well. Just as is the case with the 450, the KTM’s hydraulic clutch works flawlessly. I had no problems at all with the transmission, and the gearing felt perfect for the type of power the bike delivers. Plus, the brakes are best-in-class, by far. The incredible power combined with the lightweight feel make me confident I can stop on a dime.

Chris See – 5’10” – 165 lbs – Pro
The new 350 really feels like a 250F on the bottom end where it really lacked any pull, but it made up for it in its mid and top-end. This machine really has to be ridden like a 250F to get any power out of it but it’s a lot of fun. The transmission is very hard to shift and I had to use the clutch every time I changed gears

The fork on this machine is just way too soft overall. All the way through the stroke I needed it to be stiffer for me to be more confident. The rear shock and linkage felt good everywhere, but I did notice a nasty little spike that I could never get rid of in the middle of the stroke. With the fork being so soft the front end has a tendency to tuck in the corners, and down fast, rough sections it can get nasty headshake. 


JC Hilderbrand

Off-Road Editor| Articles | Hilde is holding down the fort at MotoUSA’s Southern Oregon HQ. With world-class dirt bike and ATV trails just minutes away, the hardest part is getting him to focus on the keyboard. Two wheels or four, it doesn’t matter to our Off-Road Editor so long as it goes like hell in the dirt.

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