AJP PR4 125 (2007 - 2021): A Lightweight Champion for Beginners and Trail Enthusiasts

Introduction

The AJP PR4 125 is a motorcycle that defies expectations. Produced by the Portuguese brand AJP—a company with deep roots in off-road racing—this nimble machine carved out a unique niche during its 14-year production run. Designed primarily for riders with A1 licenses (Europe’s 125cc learner category), the PR4 125 isn’t just a gateway bike; it’s a fully realized enduro and supermoto platform that prioritizes accessibility, durability, and pure riding joy. Available in Enduro and Supermoto configurations, this motorcycle appeals to both dirt enthusiasts and urban adventurers. Let’s dissect what makes this underdog a standout in its class.

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Design & Build: Rugged Simplicity Meets Purposeful Engineering

Chassis & Frame

The PR4 125’s backbone is a composite aluminum/steel frame—a rarity in the budget 125cc segment. The aluminum double beam reduces weight (99–112 kg / 218–247 lbs, depending on trim), while the steel cradle adds torsional rigidity. This hybrid design strikes a balance between agility and stability, whether you’re carving through single-track trails or navigating city traffic.

Suspension

• Enduro: The front forks evolved over the years, starting with basic hydraulic units and later adopting Marzocchi 40mm USD forks (adjustable for preload and rebound). These paired with a ZF Sachs monoshock offering 260–300 mm (10.2–11.8 in) of rear travel—enough to swallow rocky terrain without drama.
• Supermoto: Shorter travel suspension (260 mm front/280 mm rear) and stiffer damping prioritize road manners. Later models featured fully adjustable AJP-branded forks for fine-tuning.

Brakes & Wheels

• Enduro: A 260 mm front disc with a twin-piston caliper and 210–220 mm rear disc provide ample stopping power. Spoked 21-inch front/18-inch rear wheels (Enduro) wrapped in knobby tires (90/90-21 front, 120/80-18 rear) dominate loose surfaces.
• Supermoto: Smaller 17-inch wheels (100/80-17 front, 130/70-17 rear) with street-focused rubber improve cornering grip. Brake specs remain similar, though some variants use a larger 260 mm rear disc.

The PR4’s design ethos is clear: no frills, all function. Plastic bodywork is minimal, the seat is slim, and the overall profile screams “ready to get dirty.”

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Engine Performance: Modest Power, Maximum Fun

At its heart lies a 124cc air/oil-cooled single-cylinder engine with a SOHC 2-valve head. Fed by a 26–30 mm carburetor (Walbro or Sheng Wey, depending on year), it produces 12.5–12.6 hp (9.1–9.4 kW) at 8,400–9,000 rpm and 8.5 Nm (6.3 lb-ft) of torque peaking at 8,000 rpm. Numbers won’t set your hair on fire, but the engine’s character is where it shines:

• Low-End Grunt: The 56.5 x 49.5 mm (2.2 x 1.9 in) bore/stroke ratio prioritizes torque over top-speed theatrics. From idle to mid-range, the PR4 pulls eagerly—perfect for technical trails or zipping through traffic.
• Carbureted Charm: While fuel injection dominates modern bikes, the PR4’s carburetor simplifies maintenance. Cold starts might require patience, but once warm, throttle response is crisp.
• Indestructible?: Air cooling and a CDI ignition system keep things simple. Owners report these engines surviving years of abuse with basic care.

Top speed hovers around 100–110 km/h (62–68 mph), but the PR4 isn’t about straight-line speed. It’s about flickability, whether you’re lofting the front wheel over logs or threading through alleyways.

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On the Trail (Enduro) vs. On the Street (Supermoto)

Enduro: Born for the Dirt

Swing a leg over the Enduro variant, and the 920 mm (36.2 in) seat height reminds you this is a serious off-roader. Yet, the 99–105 kg (218–231 lb) dry weight makes it manageable for shorter riders. The suspension soaks up rooty trails and small jumps with composure, while the 365 mm (14.4 in) ground clearance shrugs off rocks.

The narrow powerband encourages aggressive clutch work, but once you’re in the groove, the PR4 dances beneath you. It’s no KTM, but for honing skills or exploring forest trails, it’s a blast.

Supermoto: Urban Playground

Lowered to 850–870 mm (33.5–34.3 in) seat height and wearing 17-inch street tires, the Supermoto transforms into a hooligan’s delight. Flick it into corners with knee-out enthusiasm—the lightweight chassis and sticky tires inspire confidence. The engine’s torque punches off stoplights, and the short wheelbase (1,360–1,410 mm / 53.5–55.5 in) lends razor-sharp turn-in.

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Competition: How Does the PR4 125 Stack Up?

The 125cc enduro/supermoto segment is fiercely competitive. Here’s how the AJP holds its ground:

1. Yamaha WR125R:
2. More refined, fuel-injected, and faster (15 hp).

3. But: Heavier (129 kg / 284 lbs) and pricier. The WR125R feels bulkier on tight trails.

4. Beta RR 125:

5. Premium components (e.g., Sachs suspension) and race-ready out of the box.

6. But: Higher maintenance costs and shorter service intervals.

7. KTM 125 EXC:

8. A powerhouse with 27 hp (for restricted markets).
9. But: Complexity and cost alienate beginners.

AJP’s Edge: The PR4 125 wins on simplicity and affordability. It’s a no-nonsense platform for learners or riders who value mechanical familiarity. While rivals offer more tech, the AJP’s lightweight and durability make it a cult favorite.

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Maintenance: Keeping Your PR4 125 Alive (and Thriving)

Key Considerations:

1. Carburetor Care: Clean the jet every 3,000 km (1,864 miles)—more often if riding in dusty conditions. Upgrade to a high-flow air filter (available at MOTOPARTS.store) for better airflow.
2. Oil Changes: Use SAE 20W-50 oil every 1,500 km (932 miles). The engine holds just 1.1 liters (2.3 US pints), so frequent changes are cheap insurance.
3. Chain Maintenance: O-ring chains last longer, but regular lubrication (every 500 km / 311 miles) is critical. Swap worn sprockets promptly to avoid drivetrain wear.
4. Suspension Tuning: Older models benefit from aftermarket fork springs or shock linkages. Check MOTOPARTS.store for ZF Sachs-compatible rebuild kits.

Common Upgrades:

• Exhaust: A free-flow slip-on (like the Dominator HP2) unlocks a throatier exhaust note and minor power gains.
• Brake Pads: EBC sintered pads improve bite, especially for Supermoto riders.
• Handlebar Risers: Enduro riders appreciate the extra leverage on technical climbs.

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Final Thoughts: Who Should Buy the AJP PR4 125?

This isn’t a bike for speed demons or tech addicts. It’s for riders who value analog thrills and mechanical simplicity. The PR4 125 excels as:
- A learner bike for building off-road fundamentals.
- A lightweight commuter that’s cheap to run.
- A project bike for customization (supermoto conversions, engine tweaks).

While newer 125s have eclipsed it in power and features, the AJP PR4 125 remains a testament to minimalist design. It’s a motorcycle that rewards skill over horsepower—and in an era of electronic aids, that’s a refreshing proposition.

Ready to personalize your PR4 125? Explore MOTOPARTS.store’s curated selection of aftermarket upgrades, from performance carb jets to durable skid plates. Your next adventure starts here.

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Specifications sheet

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