Hyosung RX 125 D SM [2011 - 2011]: A Compact Supermoto for Urban Adventures and Light Off-Road Fun

Introduction

The Hyosung RX 125 D SM occupies a unique niche in the motorcycle world. Released in 2011 as part of Hyosung’s foray into lightweight, accessible machines, this Supermoto-style bike blends street agility with just enough off-road DNA to tempt riders looking for versatility. With its punchy 125cc engine, upright ergonomics, and knobby-tire styling, it’s designed for riders who want to navigate city traffic during the week and explore gravel trails on weekends—all without breaking the bank. Let’s dive into what makes this bike tick and how it holds up over a decade after its release.

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Design & Ergonomics: Supermoto Style Meets Practicality

The RX 125 D SM’s design screams “fun-first.” Its compact steel frame, 17-inch alloy wheels wrapped in sporty 110/70 (front) and 130/70 (rear) tires, and minimalist bodywork give it a purposeful, no-nonsense aesthetic. The orange-and-black color scheme (the only options in 2011) pops on the road, while the slim profile keeps weight down to a manageable 123 kg (271 lbs).

The riding position is classic Supermoto: a tall, 840 mm (33.1-inch) seat height encourages standing on the pegs for aggressive maneuvers, but the narrow seat and well-placed handlebars make it surprisingly comfortable for shorter riders. The dashboard is basic—analog speedometer, fuel gauge, and indicator lights—but legible at a glance.

Hyosung prioritized function over frills here. Plastic components feel utilitarian, and the lack of weather protection (no fairings or windscreen) reminds you this isn’t a highway cruiser. Still, the overall build quality is decent for its class, with welded joints and fasteners showing no obvious cost-cutting.

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Performance: Small Displacement, Big Personality

Engine & Transmission

At the heart of the RX 125 D SM lies a 124cc single-cylinder, four-stroke engine with a DOHC valvetrain. Producing 13 HP (9.5 kW) at 10,000 RPM, it’s not a powerhouse, but the carbureted mill has character. Throttle response is crisp in the mid-range, and the five-speed gearbox shifts with a satisfying clunk. You’ll need to rev it hard to access peak power—ideal for zipping through traffic but less thrilling on open roads.

The engine’s oil-and-air cooling system keeps temps stable during stop-and-go rides, though sustained highway speeds (think 90-100 km/h or 56-62 mph) can feel strained. Fuel economy shines, averaging ~40 km/L (94 mpg), making it a budget-friendly commuter.

Handling & Suspension

Where this bike truly excels is agility. The 56.3-inch wheelbase and lightweight chassis let it carve through corners like a scalpel. Upside-down front forks and a rear mono shock handle urban potholes with composure, though heavier riders might find the suspension soft for aggressive off-roading. The 295 mm (11.6-inch) ground clearance (on some variants) allows for moderate trail use, but the street-biased tires limit grip on loose surfaces.

Braking

A single front disc with a twin-piston caliper provides adequate stopping power, but the rear drum brake feels underwhelming by modern standards. New riders will appreciate the forgiving nature, though seasoned motorcyclists might crave more bite during spirited rides.

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Competition: How Does the RX 125 D SM Stack Up?

In the 125cc Supermoto segment, the Hyosung faced stiff competition in 2011:

1. Yamaha WR125X: A fan favorite with a liquid-cooled engine and 15 HP. Lighter and more refined, but pricier.
2. Aprilia SX 125: Two-stroke performance (15 HP) and premium suspension, but higher maintenance costs.
3. Honda CRF125F: Trail-focused with superior off-road suspension, though less street-friendly.

The Hyosung’s advantages? Simplicity and value. Its air/oil-cooled engine lacks the complexity of liquid-cooled rivals, and the steel frame is cheaper to repair than aluminum alternatives. While it doesn’t top any performance charts, it’s a solid “jack-of-all-trades” for riders prioritizing affordability and ease of maintenance.

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Maintenance: Keeping Your RX 125 D SM in Peak Condition

Owners of the RX 125 D SM will find maintenance straightforward—a blessing for DIY enthusiasts. Key considerations:

• Oil Changes: Stick to a strict 2,000–3,000 km (1,200–1,800 mi) interval. Use 10W-40 motorcycle oil to protect the high-revving engine.
• Carburetor Tuning: Cold starts can be finicky. Clean the carb annually and consider upgrading to a premium air filter (available at MOTOPARTS.store).
• Chain Care: The O-ring chain needs regular lubrication. Replace sprockets if you notice hooked teeth.
• Brake Upgrades: Swap factory brake pads for sintered variants to improve stopping power.

Common wear items like clutch cables, throttle grips, and footpegs are widely available. For off-road riders, we recommend installing a skid plate and handguards—both offered in our store’s adventure section.

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Final Thoughts: Who Is This Bike For?

The Hyosung RX 125 D SM isn’t about cutting-edge tech or blistering speed. It’s a gateway to motorcycling freedom—a bike that forgives mistakes, sips fuel, and encourages playfulness. New riders will love its approachable powerband, while veterans might rediscover the joy of flicking a lightweight machine through tight corners.

Yes, the plastics creak, the mirrors vibrate at speed, and the exhaust note won’t stir your soul. But as a tool for urban exploration and weekend trail rides, it’s hard to beat. A decade later, its charm lies in its simplicity: just you, the throttle, and the road (or dirt path) ahead.

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Specifications sheet

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