After months of announcing its intention to create a new 350cc 4-stroke motocross bike, Austrian motorcycle manufacturer KTM gave Motorcycle USA the opportunity to ride its eagerly anticipated 2011 KTM 350 SX-F. Not only is the 350 an all-new model in KTM’s line-up, it creates an entirely new category for the motorcycle industry. It was engineered to attract both racers and recreational dirt bike riders seeking a happy-medium between the agility and high-revving performance of a 250F and the brute power and versatility of a 450F. After spending a day at the controls of it at Southern California’s fabulous Pala Raceway, we are impressed with the hybrid qualities of this unique off-road motorcycle.

ENGINE

As the nomenclature implies, the 350 SX-F uses a liquid-cooled 4-stroke single-cylinder engine. The piston slides 57.5mm inside the 88.0mm cylinder bore which equates to exactly 349.7cc of combustion volume—placing it right in between that of a 250F and 450F machines. Fuel is compressed to a ratio of 13.5:1, which is the highest measurement of any KTM off-road bike and signifies the potential



Watch the the 350 SX-F in action as we tear it up at Pala Raceway in our 2011 KTM 350 SX-F First Ride Video.
for serious engine performance across its 13,000-rpm rev range. Other hot-rod techniques include the dual camshafts driving the four titanium valve-equipped cylinder head.

Similar to the 250 SX-F, the 350 uses a dual-pump engine lubrication system. It also employs a balance shaft which acts as a water pump and camshaft drive thereby reducing engine vibration while helping to maintain petite engine dimensions. Also shared between models is the Keihin electronic fuel-injection system.

The system makes use of a single fuel injector that sprays into a 42mm throttle body. There is no fast idle or choke/cold-start knob and the system automatically meters fuel/air ratio based on atmospheric conditions. Spent fuel is passed through a stainless-steel header (without a head pipe-mounted external resonator) and a long aluminum muffler.


The 350 SX-F features a liquid-cooled 4-stroke 349.7cc single with a 88 X 57.5mm bore/stroke and the highest compression ratio amongst KTM off-roaders at 13.5:1. The FI system is powered directly by the AC generator and capacitor (attached to the throttle body). As soon as the battery-powered starter button is pressed enough electricity is generated to power the fuel-injection system. While there isn’t a conventional kick start lever, it is available as a PowerPart accessory, though we wonder why you’d ever consider its fitment with the convenience of a handlebar-mounted push button electric start.

Additional PowerPart accessories come in the form of a Map Select Switch and User Setting Tool that allow the rider to adjust engine mapping on the fly with the handlebar-mounted Map Select Switch—a first for the motocross bike world—or with your computer via the User Setting Tool.

Power is transmitted to the 110-series Bridgestone M70 rear tire through a 5-speed gearbox and 14/50 final drive gearing. The transmission is augmented by a multi-plate clutch bathed in engine oil. The clutch also features hydraulic actuation for light lever pull as well as resistance to fade during prolonged hard use.


The rear end of the 2011 350 SX-F features a traditional linkage suspension with a cast aluminum swingarm and a longer WP gas-charged shock absorber. In terms of engine maintenance, like the rest of the KTM line, accessing and replacing the engine’s foam air filter can be accomplished without any tools.

CHASSIS

The biggest news in the chassis department is the incorporation of a traditional linkage-equipped rear suspension system. That’s right, the Austrian’s finally succumbed to the alleged benefit of a linkage. In fact, it’s now employed it across the entire ’11 SX-F line. The 2-strokes however still retain the direct PDS-style rear suspension as it is claimed to still be superior for that application.

A longer WP gas-charged shock absorber attaches between the redesigned upper frame mount and linkage located below the cast aluminum swingarm (which is also new and is constructed from a single cast of aluminum without welds). Over a foot of rear suspension travel is available. The shock has received some updates including a new piston and bushings to compensate for the greater shock shaft velocity. The shock still retains adjustability for spring preload, high and low-speed compression, and rebound damping.

The Austrians insist on using a chromoly steel frame as construction is claimed to be lighter and provide more space for some of the bikes major components, including the 1.98-gallon fuel tank. The frame is similar in design to the 250 and 450 SX-F and features greater resistance to side-to-side twisting force as compared to previous SX-F frames. It is also slightly less rigid from front-to-back to compensate for the reworked re
A WP 48mm fork with new spring and valving settings and 11.8-in. of travel is ready to cushion landings when it's big-air time. ar suspension.

Beautifully machined triple clamps carved from solid pieces of aluminum grace the front end and the steering head angle is 26.5 degrees. The clamps hold a WP 48mm fork with new spring and valving settings tuned specifically for the demands of the 350. Suspension travel is rated at 11.8-inches and the fork offers compression and rebound damping adjustment.

The bike rolls on a set of silver Excel wheels with machined aluminum hubs. The wheels are shod with Bridgestone tires in sizes 80/100-21 up front and 110/90-19 out back. Each wheel makes use of a wave-style brake disc each actuated by a Brembo caliper hydraulically through stainless-steel brake lines.

Engineers spent a good deal of time trying to perfect the rider interface with the help of World Motocross champ Stefan Everts. Its sleek orange bodywork has a smooth, streamlined shape and reduces the likelihood of rider’s clothing getting caught on the bike during cornering and aerial maneuvers.

The side body panels are contoured so it is easy to move about. The bike also features a wide and long rear fender to keep dirt off the rider. The oversized footpegs are a nice touch as is the Renthal handlebar and soft, yet durable hand grips. Another nice touch is the clever number plate hand hold which makes it easier to lift the bike on and off its stand.

“It pulls hard but it doesn’t have that jump out of your hands feeling. The power is just really tractable and easy to manage. It’s really smooth plus it revs to the moon," said pro level test rider, Matt Armstrong.
RIDING IMPRESSSION

Lift the bike off the stand and the first thing you’ll notice is the well-placed hand hold which makes the task easier. While the 350 doesn’t feel quite as light as a 250F it’s close and certainly feels lighter than a 450.

Hop into the seat and it feels a bit wider and just a hair taller compared to a 250F, which is surprising considering that the seat height is claimed to be identical between both KTM machines (39.06 in.). There’s no key, on/off fuel petcock, or run/start switch so to get going is literally as easy as pushing the right-hand side starter button.

Right off the bottom you can feel the engine’s extra cc compared to a 250F. The engine exhaust note sounds beefy but isn’t overly obnoxious, courtesy of the quiet muffler. Pin the throttle and you’ll notice that the engine has a voracious appetite for revs. It gains rpms quick much like a 250F and overall engine performance can be described as snappy and immediately responsive to throttle input.


Matty does his best Mike Alessi impersonation on KTM's latest dirt shredder. Mid-range engine performance is strong and feels similar to that of a mildly-tuned 250F. But as you get higher in the rev range the engine zings to life delivering an astounding amount of power for its displacement. Here acceleration begins to feel similar to that of a 450 bike. The engine pulls hard with a 450 sense of urgency; however, its perfectly calibrated fuel and ignition settings make it surprisingly easy to control.

“I like the motor a lot,” said our pro level test rider Matt Armstrong. “It pulls hard but it doesn’t have that jump out of your hands feeling. The power is just really tractable and easy to manage. It’s really smooth plus it revs to the moon. I mean, I never even felt the rev limiter all-day. It revs out that far!”

Part of the reason why the KTM feels so fast is how effectively it puts power down to the ground. It’s especially noticeable when exiting a somewhat slippery corner. Where a 450 would have the propensity to spin the rear tire, the 350’s smoother, more obedient powerband helps the rear tire dig into the ground which in turn drives you forward.


Handling on the new 350 feels similar to a 250 and carves turns with comparable agility. Steering is light and predictable. While the engine’s character is impressive, perhaps even better is its handling. Despite feeling larger and heavier at a standstill, at speed the 350 carves into a turn with the same level of agility as its 100cc smaller sibling. Steering is light and predictable, plus the bike tracks well during a turn. We also appreciated that its cornering agility doesn’t come at the price of stability.

“I really enjoy the way the bike handles,” stated Armstrong. “Compared to the 450 it feels like it turns sharper. It also felt a bit shorter in terms of wheelbase, which I like. The bike was really easy to control in the air. All in all it’s just a fun, easy motorcycle to ride.”

Considering the smooth track conditions it was really difficult to get a feel for the suspension and whether or not the linkage made a difference in terms of rear suspension performance. What we can tell you is that the suspension is balanced front-to-back and that bike tracked straight as an arrow even through faster sections of the track. Again, we’ll need to ride the bike at rougher tracks to truly get a feel for how the new suspension performs.

One of the best features of KTM’s SX-F line is its balanced ergonomics. As opposed to some brands of dirt bikes, the KTM is designed to fit a wide range of riders. Both myself (6-foot tall) and Armstrong (5-foot, 7-inches tall) were pleased with the way the bike fit us. We liked the oversized footpegs, handlebars and the shape of the frame rails, seat, and shrouds that allowed us to ply our bodies without any sort of hindrance.

After turning laps on the 2011 350 SX-F, we understand better how Mike Alessi was able to win Moto 2 at Hangtown on the newest KTM motocross bike.
FINAL THOUGHTS

So does the $8499 350 SX-F live up to the hype? We’d say so. The engine provides the best of both worlds. It has beefier power delivery throughout the rev range, yet still retains explosive top end power. Even better is that the power is friendly to use and won’t rip your arms out. And who can forget that starting the engine is as easy as a push of a button. Handling was excellent and while we’ll need more saddle time to fully understand the suspension we can tell you that it is without question an easy, and most importantly, fun motorcycle to ride.