KTM 250 SX (2017-2021): A Two-Stroke Motocross Legend Revisited

Introduction

The KTM 250 SX has long been a cornerstone of motocross racing, and the 2017–2021 generation solidified its reputation as a razor-sharp tool for riders who live by the mantra "ready to race." This Austrian two-stroke isn’t just a motorcycle—it’s a statement. Designed for aggressive track use, it balances raw power with precision engineering, all wrapped in KTM’s signature orange armor. After spending time aboard this machine, it’s clear why it’s remained a favorite among privateers and weekend warriors alike. Let’s dive into what makes this generation tick—and why it still turns heads (and laps) years later.

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Engine Performance: Two-Stroke Fury, Refined

At the heart of the KTM 250 SX lies a 249cc liquid-cooled two-stroke single-cylinder engine. The bore and stroke of 66.4 mm x 72 mm (2.6 x 2.8 inches) create a powerband that’s both explosive and surprisingly manageable. Unlike older two-strokes that demand constant clutch work, this engine pairs its frenetic top-end rush with a meaty midrange, thanks to KTM’s reed intake system and Mikuni TMX 38mm carburetor.

Riding the 250 SX feels like wrestling a lightning bolt. Crack the throttle open out of a corner, and the front wheel floats skyward with minimal effort. The hit is sharp but not overwhelming, making it easier to modulate power on slick tracks. For a carbureted bike, throttle response is crisp, though riders in extreme elevations might still yearn for fuel injection (a realm KTM reserved for its four-strokes during this era).

Key Highlights:
- Peak Power: Estimated 48–50 HP, with a screaming 9,000+ RPM redline.
- Gearbox: The 5-speed transmission is bulletproof, with a light pull from the Brembo hydraulic clutch. First gear is low enough for technical sections, while fifth lets you stretch legs on long straights.
- Soundtrack: The raspy two-stroke exhaust note is pure motocross nostalgia—a chainsaw symphony that’s music to any dirt rider’s ears.

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Handling & Suspension: WP’s Track-Tuned Mastery

KTM’s partnership with WP Suspension shines here. The 48 mm WP XACT-USD fork (rebranded from earlier AER 48 models) offers 310 mm (12.2 inches) of travel, while the rear XACT monoshock delivers 300 mm (11.8 inches). Both ends are fully adjustable, letting you dial in settings for everything from hardpack to sand whoops.

On the track, the chassis feels telepathic. The chrome-molybdenum steel frame strikes a balance between rigidity and flex, inspiring confidence when railing berms or landing from jumps. At 87.5–96 kg (193–210 lbs) dry, it’s one of the lightest bikes in its class—a trait you’ll appreciate when fatigue sets in during moto two.

Notable Features:
- Brakes: Brembo’s four-piston front caliper bites a 260 mm disc, offering stoppage power that’s almost too strong for newcomers.
- Ergonomics: The flat seat and narrow body make it easy to shift weight forward under braking or rearward for acceleration.
- Wheels & Tires: Excel rims wrapped in Dunlop Geomax MX3S tires provide predictable grip, though hardcore racers often swap to softer compounds.

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Chassis & Ergonomics: Built for Attack

Standing at 850–960 mm (33.5–37.8 inches), the seat height accommodates shorter riders better than most MX bikes—provided you’re comfortable with a aggressive riding stance. The handlebars are positioned to encourage an attack-oriented posture, and the footpegs sit low enough for easy weight transitions.

Ground clearance of 375 mm (14.8 inches) ensures minimal drama over rocks or ruts, while the 1495 mm (58.9-inch) wheelbase keeps the bike stable at speed without sacrificing cornering agility.

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Competition: How Does It Stack Up?

The 250cc two-stroke class is niche but fiercely competitive. Here’s how the KTM 250 SX fares against its rivals:

1. Yamaha YZ250

• Power: Yamaha’s air-cooled engine feels softer off the bottom but lacks the KTM’s top-end frenzy.
• Suspension: KYB units are plush but less adjustable than WP’s offerings.
• Weight: At 103 kg (227 lbs), the YZ250 feels portly compared to the featherweight KTM.

2. Honda CRF250R (Four-Stroke)

• Engine: Honda’s four-stroke is smoother and easier for beginners, but it can’t match the 250 SX’s explosive power-to-weight ratio.
• Maintenance: Four-strokes demand more frequent (and costly) top-end rebuilds—a win for KTM’s simpler two-stroke.

3. Husqvarna TC 250

• Similarities: Shares the same engine and chassis as the KTM but adds a composite subframe and Magura brakes.
• Differentiator: Husky’s styling and slightly plusher suspension attract riders who prioritize comfort over outright aggression.

Verdict: The KTM 250 SX dominates for riders who want a lightweight, high-revving weapon with minimal fuss. Its two-stroke simplicity and premium components make it a better long-term investment than most four-strokes in its class.

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Maintenance: Keeping the Orange Beast Alive

Owning a KTM 250 SX is relatively straightforward—if you’re disciplined. Here’s what to watch:

1. Top-End Rebuilds

• Two-strokes need piston replacements every 30–50 hours. Use a quality ring set (like Vertex or ProX) and inspect the cylinder for scoring.
• Pro Tip: Keep spare gaskets and circlips in your toolbox.

2. Air Filter Care

• The Mikuni carb is sensitive to dirt. Clean the air filter after every ride and oil it with a tacky formula like Motorex.

3. Suspension Servicing

• WP forks need fresh oil every 40 hours. Upgrade to SKF seals if you’re battling mud regularly.

4. Chain & Sprockets

• The 520 X-ring chain lasts longer than most, but swap sprockets as a set to avoid uneven wear.

5. Brake Fluid

• Flush with DOT 4 or 5.1 fluid annually to prevent sponginess.

6. Cooling System

• Use ethylene glycol-based coolant and check hoses for cracks after heavy crashes.

MOTOPARTS.store Recommendations:
- Upgrade to an aftermarket exhaust (FMF or Pro Circuit) for better throttle response.
- Swap stock handlebars for a Renthal TwinWall if you’re prone to bending components.
- Install a hour meter to track maintenance intervals accurately.

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Final Thoughts: Why the 250 SX Still Matters

The 2017–2021 KTM 250 SX isn’t just a holdover from the two-stroke era—it’s a reminder of why lightweight, high-revving bikes are irreplaceable on the track. Its combination of brutal power, agile handling, and low maintenance costs makes it a standout choice for riders who value performance over pomp.

Whether you’re chasing holeshots or just love the smell of premix in the morning, this KTM deserves a spot in your garage. And when it’s time to rebuild, upgrade, or tweak, MOTOPARTS.store has the parts to keep your SX shredding for years to come.

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Specifikacijų lentelė

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