2021 KTM 450 SX-F Review: A Motocross Weapon Refined for Battle

Introduction

The 2021 KTM 450 SX-F isn’t just a dirt bike – it’s a factory-ready motocross machine that blurs the line between production motorcycle and race prototype. As the final evolution of KTM’s fourth-generation 450 SX-F platform, this single-year model represents the culmination of years of development in Austrian engineering. Designed for riders who demand podium-level performance straight out of the crate, this orange beast combines brutal power delivery with shockingly precise handling. After spending a day wrestling this machine around a rugged MX track, I came away equal parts exhausted and impressed by its ability to dominate technical terrain.

Design & Ergonomics: Purpose-Built Aggression

Clocking in at just 100 kg (220.5 lbs) dry weight, the 450 SX-F feels more like a 250-class machine when you first throw a leg over its 950mm (37.4") seat. The radical weight reduction comes from KTM’s obsessive use of premium components: - CNC-machined hubs shaving rotational mass
- Lithium-ion battery cutting 1.5 kg vs traditional units
- Hollow chromoly steel frame with calculated flex zones

The signature orange powder-coated frame pops against black Excel rims, while the bodywork follows KTM’s "Ready to Race" minimalist philosophy. Narrow radiator shrouds (housing twin WP radiators) let you grip the bike with your knees like a trials machine, crucial when navigating rutted corners. At 370mm (14.6") of ground clearance, you’ll rarely drag components even through the gnarliest whoops.

Engine Performance: Controlled Fury

At the heart beats a 449.3cc SOHC powerplant pumping out 63 HP (46 kW) – numbers that would be respectable for a 600cc street bike, let alone a 450cc dirt weapon. What’s shocking isn’t the peak output but how usable it remains across the rev range:

• Low-End: The 95mm bore creates instant torque off idle, tractoring up hills without clutch abuse
• Mid-Range: Keihin EFI delivers crisp throttle response between 5,000-8,000 RPM
• Over-Rev: Despite being a big-bore, it willingly screams to 11,500 RPM when needed

The 4-speed transmission (a deliberate choice over 5-speed for weight savings) features a dedicated motocross ratio spread. Third gear becomes your Swiss Army knife – capable of launching off 60-foot tables or negotiating technical rhythm sections. Unlike carbureted competitors, the fuel-injected engine remains unfazed by altitude changes or temperature swings.

Suspension & Handling: WP’s Masterclass

KTM’s partnership with WP results in the best stock suspension in motocross. The 48mm WP XACT USD fork offers 310mm (12.2") of travel via a unique sealed cartridge design that eliminates oil mixing. Paired with the XACT rear shock (300mm/11.8" travel), the setup provides: - Initial Stroke: Plushness over small chop
- Mid-Stroke: Progressive resistance for G-out landings
- Bottoming Resistance: Hydraulic stops prevent harsh metal-on-metal impacts

With a 26.1° rake and 1485mm (58.5") wheelbase, the bike strikes a perfect balance between straight-line stability and cornering agility. During my test, the front end stuck to hardpack berms like Velcro, while the chassis remained composed through braking bumps that would unsettle Japanese competitors.

Competition: Class of 2021 Showdown

The 450cc motocross segment saw fierce competition in 2021. Here’s how the KTM stacked up:

1. Yamaha YZ450F
2. Advantage: Broader powerband, tuner app connectivity

3. KTM Counter: 3.5 kg lighter, superior air filter access

4. Honda CRF450R

5. Advantage: Lower seat height (960mm vs 950mm)

6. KTM Counter: More advanced chassis flex, hydraulic clutch

7. Husqvarna FC 450

8. Advantage: Magura clutch components, composite subframe
9. KTM Counter: $500 cheaper MSRP, better parts availability

Where the 450 SX-F truly shines is race readiness. While competitors require aftermarket exhausts or ECU tunes to unlock full potential, the KTM arrives track-ready with a DDS clutch and Brembo brakes that most riders never need to upgrade.

Maintenance: Keeping the Beast Alive

As a MOTOPARTS.store journalist, I must emphasize that even this engineering marvel needs proper care. Key maintenance considerations:

1. Air Filter Service
The twin-air foam filter requires cleaning every 3-5 hours. Use MOTOPARTS.store’s No-Toil Bio Air Filter Oil ($14.99) for hassle-free, biodegradable maintenance.

2. Suspension Refresh
WP recommends changing fork oil every 30 hours. Our WP 2.5W Suspension Fluid ($29.95/liter) maintains plushness between professional services.

3. Chain & Sprocket Care
The 520 chain demands regular adjustment. Pair MOTOPARTS.store’s DID ERV3 Gold Chain ($129.99) with a TM Designworks Slide N Guide Kit ($179.95) to prevent derailments.

4. Cooling System
Use only ethylene glycol-based coolant mixed 50:50 with distilled water. Our Engine Ice Hi-Performance Coolant ($24.95) reduces boil-over risks in technical sections.

5. Brake Maintenance
Brembo’s floating calipers work best with MOTOPARTS.store’s BrakeTech Brake Pads ($69.95 front/$59.95 rear), offering 20% longer lifespan than OEM.

Conclusion: The Apex Predator

The 2021 KTM 450 SX-F isn’t for casual riders – it’s a razor-sharp tool demanding skill and commitment. Yet for those willing to harness its capabilities, few motorcycles offer this level of track dominance straight from the showroom. From its telepathic suspension to the explosive yet controllable power delivery, every component serves the singular purpose of winning motos. While the 4-speed transmission might intimidate trail riders, motocross purists will appreciate its focused intent. Two years later, it remains a benchmark for what a production motocross bike can achieve.

Specifications sheet