KTM 350 SX-F [2021 - 2021]: The Middleweight Motocross Precision Tool
Introduction
The KTM 350 SX-F has long occupied a unique niche in the motocross world—bridging the gap between agility-focused 250cc machines and the raw power of 450cc beasts. The 2021 iteration of this Austrian-engineered machine refines this balance further, offering riders a weapon that’s as at home on tight, technical tracks as it is charging through sweeping outdoor circuits. Designed for riders who demand precision without sacrificing versatility, the 350 SX-F continues to be a favorite among competitive amateurs and seasoned pros alike. Let’s dive into what makes this bike tick—and why it might just be the perfect upgrade for your motocross arsenal.
Design & Ergonomics: Built for Attack
KTM’s signature orange-and-black livery screams aggression, but the 350 SX-F’s design is more than just eye candy. With a 950 mm (37.4-inch) seat height, this bike positions riders in a commanding stance, ideal for tackling jumps and ruts. The Central double-cradle 25CrMo4 steel frame keeps the dry weight at a featherlight 99.5 kg (219.4 lbs), making it one of the most nimble bikes in its class.
The bodywork is slim where it counts—between the knees and thighs—allowing for easy weight shifts mid-corner. Renthal Fatbar handlebars come standard, offering adjustability for personalized control. Even the footpegs are strategically angled to maximize grip when the track gets muddy.
Key Highlights:
- WP XACT-USD 48 mm forks up front with 310 mm (12.2 inches) of travel.
- WP XACT Monoshock rear suspension with 300 mm (11.8 inches) of wheel travel.
- Brembo hydraulic clutch and brakes for consistent modulation.
The bike’s 370 mm (14.6 inches) of ground clearance ensures obstacles like logs or deep ruts won’t scrape the underbelly, while the 7-liter (1.85-gallon) fuel tank is ample for moto sprints.
Performance: Where Precision Meets Power
Engine & Transmission
The 2021 KTM 350 SX-F’s 349.7 cc liquid-cooled single-cylinder engine is a masterpiece of balance. With a 88.0 x 57.5 mm (3.5 x 2.3-inch) bore/stroke ratio, it prioritizes quick-revving responsiveness over brute force. The Keihin engine management system ensures crisp throttle response, whether you’re feathering through berms or pinning it down a straightaway.
Riders will appreciate the electric starter—a luxury in the motocross world—paired with a 2Ah lithium battery that stays reliable even in cold conditions. The 5-speed gearbox is slick, with short throws between gears, while the Brembo-controlled wet multi-disc clutch allows for seamless power delivery.
On the Track:
- Low-end torque pulls hard out of corners, but the real magic happens in the mid-range.
- The engine avoids the "light switch" powerband of some 450s, making it forgiving for riders still honing their throttle control.
- At high RPMs, the exhaust note sharpens into a satisfying snarl—a reminder that this bike means business.
Suspension & Handling
The WP XACT suspension setup is sublime. On choppy terrain, the forks absorb small bumps without sacrificing feedback, while the rear monoshock stays planted during hard acceleration. For bigger jumps, stiffening the compression damping (a quick adjustment via hand tools) adds confidence.
The 26.1° rake angle and lightweight chassis make steering almost telepathic. Flicking the bike through rhythm sections feels effortless, and the Bridgestone Battlecross tires (standard issue) dig into loose dirt with tenacity.
Competition: How Does It Stack Up?
The 350cc motocross segment is fiercely competitive. Here’s how the KTM 350 SX-F holds its ground:
vs. Husqvarna FC 350
The Husqvarna FC 350 shares much of its DNA with the KTM (same engine, similar frame), but differences emerge in the details. Husky’s composite carbon fiber subframe shaves marginal weight, while its Pro Taper handlebars offer a slightly flatter bend. However, the KTM’s suspension feels more progressive on hard landings, and its Brembo brakes outperform Husqvarna’s Magura units in muddy conditions.
vs. Yamaha YZ250F
Yamaha’s 250F is lighter (98 kg / 216 lbs) and cheaper, but it can’t match the KTM’s power output. The YZ250F’s engine thrives on high RPMs, demanding aggressive riding, whereas the 350 SX-F’s broader torque curve suits varied skill levels. The Yamaha also lacks an electric starter—a glaring omission for modern motocross.
vs. Honda CRF450R
The CRF450R packs more brute force, but its 123 kg (271 lbs) weight becomes apparent in tight sections. The Honda rewards expert riders who can muscle it around, while the KTM feels more accessible for intermediate riders seeking speed without exhaustion.
Maintenance: Keeping Your 350 SX-F in Fighting Shape
Critical Checks for Peak Performance
- Chain & Sprockets: The 520 chain requires regular lubrication and tension adjustments. A slack chain risks derailment; too tight, and you’ll strain the transmission.
- Brake Fluid: Use DOT 4 or 5.1 fluid for the Brembo system. Flush annually to prevent moisture buildup.
- Cooling System: The Water+ coolant mixture needs replacement every 40 hours. Check hoses for leaks after heavy rides.
- Air Filter: Clean every 2-3 rides. A clogged filter starves the engine of air, robbing power.
- Tire Pressure: Stick to 1.0 BAR (14.5 PSI) front and rear for optimal grip. Overinflation reduces traction; underinflation risks pinch flats.
Upgrade Recommendations from MOTOPARTS.store
- High-Performance Air Filters: Boost airflow and extend service intervals.
- Aftermarket Suspension Springs: Tailor your setup for your weight and riding style.
- Durable Chain Kits: O-ring chains last longer in sandy or muddy conditions.
Conclusion: The Middleweight Champion
The 2021 KTM 350 SX-F isn’t just a bike—it’s a scalpel for dissecting motocross tracks. It rewards precision riders with its nimble chassis and torquey engine, yet remains approachable enough to help intermediates build confidence. While competitors lean toward specialization (the Husqvarna for weight weenies, the Honda for power addicts), the KTM strikes a rare balance between agility and authority.
Whether you’re chasing podium finishes or just love the thrill of a perfectly executed corner, this bike deserves a spot in your garage. And when it’s time to tweak, tune, or overhaul, MOTOPARTS.store has the gear to keep your 350 SX-F shredding harder, longer.
Ready to dominate the track? Your next upgrade is just a click away.
Specifications sheet
| Engine | |
|---|---|
| Stroke: | Four-stroke |
| Fuel system: | Fuel Injection |
| Displacement: | 350 ccm |
| Bore x stroke: | 88.0 x 57.5 mm (3.5 x 2.3 in) |
| Configuration: | Single |
| Cooling system: | Liquid |
| Number of cylinders: | 1 |
| Dimensions | |
|---|---|
| Dry weight: | 100 |
| Seat height: | 950 mm (37.4 in) |
| Ground clearance: | 370 mm (14.6 in) |
| Fuel tank capacity: | 7.0 L (1.85 US gal) |
| Drivetrain | |
|---|---|
| Clutch: | Wet multi-disc clutch, Brembo hydraulics |
| Chain type: | 520 |
| Final drive: | chain |
| Transmission: | 5-speed |
| Electrical | |
|---|---|
| Ignition: | Keihin EMS |
| Maintenance | |
|---|---|
| Brake fluid: | DOT 4 / DOT 5.1 |
| Recommended tire pressure (rear): | 1.0 bar (14.5 psi) |
| Recommended tire pressure (front): | 1.0 bar (14.5 psi) |
| General Information | |
|---|---|
| Battery: | 2Ah Lithium battery |
| Starter: | Electric |
| Category: | Cross / motocross |
| Color options: | Orange/white/black |
| Chassis and Suspension | |
|---|---|
| Frame: | Central double-cradle-type 25CrMo4 steel |
| Rear brakes: | Single disc |
| Front brakes: | Single 220 mm disc |
| Rear suspension: | WP XACT Monoshock with linkage |
| Front suspension: | WP XACT-USD, Ø 48 mm |
| Rake (fork angle): | 26.1° |
| Rear wheel travel: | 300 mm (11.8 in) |
| Front wheel travel: | 310 mm (12.2 in) |
