If you’re into racing dirt bikes, then Thanksgiving in Southern California means one thing: Troy Lee Designs and Elrod Racing’s A Day in the Dirt Motocross Grand Prix. For the second year in a row MotoUSA participated in the annual competition, this time at Pala Raceway aboard a pair of 2011 KTM
SX-F motocrossers. We chose the 450 and 350 SX-F to compare and contrast the differences in a true racing context, where both man and machine are put to task. We’re splitting these race tests into two individual reviews by model. For the feature on the 450 see the 2011 KTM 450 SX-F Race Test
2011 KTM 350 SX-F
KTM is the first motorcycle manufacturer to offer riders a motocross bike that slots between the 450 and 250 class with its 350 SX-F. It’s designed specifically for those that seek a dirt bike with the agility and rider friendliness of a 250 and the top-end power of a 450. Accordingly, its price tag also strides between both classes, costing $300 less than the 450 SX-F ($8499) and $800 more than the 250 SX-F ($7699).
Based on our experience at the ‘09 A Day in the Dirt grand prix at the now extinct LACR (read about it in the LACR Motocross Track Shuts Down
article) where hill climbing engine torque reigned supreme, we assumed that the 350 might struggle. And while the course at Pala featured a couple hills and three long straightaways, there were also a few narrow slow-speed turns. And it’s here where this hybrid motocrosser really stands out.
Although it only weighs four pounds less than its 100cc larger sibling (246 vs. 250 pounds) in motion the difference feels like it’s multiplied tenfold. Where the 450 rider has to set-up earlier in order to nail inside ruts, at the helm of the 350 you can select any line, inside or outside, with less effort.
“The track was smooth and fast and definitely not as technical as the previous years at LACR but still a great layout,” said intermediate-level test rider Nick Thiel. “The 350 worked great in all of the tighter sections and was extremely nimble and easy to switch lines on. Wherever you wanted to go it went and did it well whether inside or outside. It worked great.”
The 350 SX-F’s milder bottom-end power helps the rear tire hook-up out of corners.
Similar to the 450, steering is neutral but overall stability, especially at speed, was superior due in part to its more optimum suspension balance. This came courtesy of stiffer spring rates (our 350 featured heavier fork [0.50 kg/mm] and shock [5.7 kg/mm] springs compared to stock).
While the spring rates felt in the ballpark for both of our 175-pound bodies, we both agreed that the fork could have more damping when loaded mid-stroke. We attempted to fix the issue by adding more compression but ran out of adjustment. However, it’s worth noting that damping was consistent and fade-free through the duration of all of our motos throughout the weekend.
Dial-in some throttle and the engine responds with the same urgency as the carbureted 450, only there is zero chance of engine hesitation or bog courtesy of its fuel-injection system. While it doesn’t offer anywhere near the bottom-end torque of the 450, its mellower initial torque output helps the rear Bridgestone tire hook up better, especially on slick terrain.
Keep the twist grip pinned and the engine spools up quicker than the 450. Mid-range pull is strong yet doesn’t overwhelm the rider and/or tire. Power transitions smoothly into a concentrated top-end that feels like it is never going to stop pulling. Looking at the dyno chart shows that rpm is key to getting the most out of the engine as it pumps out upwards of 45 horsepower from 9000 to its 11,900 redline (on par with other brand’s 450s but still almost eight down on the 450 SX-F.)
The 350 SX-F makes use of a fuel-injected engine which eliminates the chance of dreaded engine bog.
It’s deceiving how quick the bike is because it doesn’t launch forward with the same voracious front wheel in the sky madness of a 450, yet I distinctly remember drag racing neck and neck with 450s down straightaways with the rider who braked later winning the battle into the turn. Fortunately, the KTM has phenomenal stock brakes that are powerful, fade-free and offer a ridiculously high-level of feel which make them easy to manipulate aggressively.
“I started off by taking the holeshot over all 23 450s on my line,” commented Thiel in regards to Saturday’s Stunt Open GP, which he won. “After the first lap I sprinted. By Lap 4 I took a look around and saw I gapped most of my line. After that I cruised for the rest of the race before taking the win. The motor was absolutely awesome and with the layout of the track it didn’t feel like it was lacking anywhere.”
Generally we were pleased with the 350’s drivetrain. The clutch features a light lever pull and is very responsive. Final drive gearing was on the tall side but worked well on a faster GP-style track. In the first couple motos the gearbox worked great, exchanging gears without issue, but as time increased on the hour meter we started experiencing shifting gremlins. We attempted to address the problem by changing the oil, which solved the problem. So it’s important to use an high-quality engine oil (we used Motorex 10W-50 engine oil) and change it along with the filter at least every five hours to reduce the chance of problems.
For the most part, the Austrians have done a marvelous job creating a dirt bike that blends some of the attributes of both the 250 and 450 classes. Aside from the light rider friendly (soft) suspension springs we can’t find much we don’t like about it. Sure it doesn’t have the same broad and immediate hit of power as a 450, but keep the throttle pinned and rpm up and it truly does belt out 450-like power. Plus it feels much lighter and more maneuverable in motion, which makes it easier to ride at tracks like Pala’s Day in the Dirt course.
Engine: Liquid-cooled 350cc Single, DOHC, 4-valve
Bore/Stroke: 88.0 x 57.5mm
Compression Ratio: 13.5:1
Starting: Electric (optional kick-start)
Fueling: Keihin electronic fuel-injection
Clutch: Wet multi-plate, hydraulic actuation
Transmission: 5-speed, chain final drive
Final Drive Gearing: 14F/50
Frame: Chromoly steel
Front Suspension: WP 48mm fork; 2-way adjustable for compression and rebound damping; 11.8-in. travel
Rear Suspension: Linkage-equipped WP 5018 gas charged shock absorber; 4-way adjustable for spring preload, high/low-speed compression, and rebound damping; 12.48-in. travel
Front Brake: 260mm disc with Brembo dual-piston caliper, stainless-steel brake line
Rear Brake: 220mm disc with Brembo single-piston caliper, stainless-steel brake line
Handlebar: Tapered Renthal
Tires: Bridgestone M59 80/100-21, M70 110/90-19
Steering Head Angle: 26.5 deg.
Wheelbase: 58.86 in.
Ground Clearance: 14.76 in.
Seat Height: 39.06 in.
Fuel Capacity: 7.5 liters/1.98 U.S. gallons
Claimed Dry Weight: 230.2 lbs.