GAS GAS TXT 125 (2011-2015): A Trials Machine Built for Precision and Agility

Overview

The GAS GAS TXT 125, produced between 2011 and 2015, represents a golden era for lightweight trials motorcycles. Designed for technical terrain and rider finesse, this Spanish-built machine has earned its stripes in competitive trials circles and remains a favorite among enthusiasts who value agility and mechanical simplicity. With its signature red/white/black livery and race-bred components, the TXT 125 is more than just a bike—it’s a precision tool for conquering obstacles.

After spending a day throwing this 66 kg (145.5 lbs) featherweight through rocky trails and steep inclines, one thing becomes clear: this motorcycle prioritizes control over comfort, and that’s exactly what trials riders demand. Let’s dissect what makes this generation special.

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Engine Performance: Two-Stroke Simplicity at Its Finest

At the heart of the TXT 125 lies a liquid-cooled, single-cylinder two-stroke engine displacing 124.8–125 cc (7.62–7.63 cubic inches). The Dell’Orto PHBL26BS carburetor delivers crisp throttle response, while the CDI ignition ensures reliable spark even during brutal climbs.

Key characteristics:
- Power delivery: Linear and manageable for a 125cc, with a meaty mid-range that helps loft the front wheel over logs.
- Clutch action: The GG 1/3 hydraulic-diaphragm clutch is butter-smooth, allowing millimeter-perfect modulation during tricky sections.
- Gearing: The 6-speed transmission is rarely fully utilized in trials (most action happens in 1st–3rd), but it’s reassuringly durable.

The 1:50 fuel/oil mix (or 2.5% premix) keeps the engine lubed without excessive smoke. While modern fuel-injected bikes have since emerged, there’s an undeniable charm to tuning the carb for altitude or temperature—a ritual that connects rider and machine.

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Chassis and Suspension: Dancing with the Terrain

The Chrom-Molybdenum tubular frame strikes a perfect balance between rigidity and flex. Paired with a wheelbase of 1,325–1,340 mm (52.2–52.8 inches), the TXT 125 feels like an extension of your body when pivoting around tight turns or balancing on rear wheels.

Suspension highlights:
- Front: Marzocchi 40 mm Right-Sight-Up forks (adjustable compression/rebound on Racing models) offer 177 mm (7.0 inches) of travel. They absorb square-edged rocks without drama.
- Rear: Earlier Pro models used Sachs shocks, while Racing editions featured Reiger or Öhlins units. All variants provide 164 mm (6.5 inches) of controlled travel via aluminum swingarms.

The suspension setup favors responsiveness over plushness—this isn’t a bike for soaking up whoops, but for precise placement. At 650 mm (25.6 inches), the seat height is accessible, though you’ll rarely sit down in trials use.

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Brakes and Wheels: Surgical Stopping Power

- Front brake: A floating 4-piston disc setup (Galfer ‘Wave’ on Racing models) delivers bite without grabiness. You can feather it mid-climb to adjust front-end lift.
- Rear brake: The 2-piston disc is progressive, critical for controlling slides during descents.

The lightweight aluminum spoked wheels (21-inch front, 18-inch rear) wear trials-specific tires (2.75-21 front, 4.00-18 rear). These provide tenacious grip on wet roots and loose gravel, though serious competitors often upgrade to grippier rubber.

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Competition: How the TXT 125 Stacks Up

In the 125cc trials segment, the GAS GAS faced stiff competition:

1. Beta Evo 125
2. Similar weight and power, but with a slightly softer suspension setup.

3. Beta’s clutch has a lighter pull, but GAS GAS counters with better heat management during prolonged slipping.

4. Sherco ST 125

5. Sherco’s frame geometry feels more “flickable” at speed, but the TXT 125 dominates in slow-speed stability.

6. GAS GAS maintenance is simpler due to the carburetor (vs. Sherco’s occasional EFG gremlins).

7. Montesa Cota 4RT

8. Montesa’s 4-stroke engine is quieter and torque-rich, but purists argue the TXT’s two-stroke delivers sharper response.

Verdict: The TXT 125 holds its own with superior suspension adjustability and a vocal two-stroke character that thrills traditionalists.

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Maintenance: Keeping the TXT 125 in Peak Condition

As a MOTOPARTS.store journalist, here’s how to ensure longevity and performance:

1. Engine Care
2. Carb tuning: Clean the Dell’Orto jetting monthly if ridden in muddy conditions. Consider a JD Racing Jet Kit for altitude adjustments.

3. Cooling system: Flush coolant annually—the compact radiators clog easily with debris.

4. Suspension

5. Replace fork seals every 80–100 hours. Upgrade to SKF seals for durability.

6. Sachs/OEM shock rebuild kits are affordable and widely available.

7. Brakes

8. Galfer brake pads (model G1374) improve bite over stock.

9. Bleed the hydraulic clutch annually with Motorex Mineral Oil.

10. Chain/Drivetrain

11. A DID 520VT2 narrow chain reduces drag. Pair with a JT Sprockets kit for longevity.

Pro tip: Keep the air filter pristine—twin-air foam filters with No-Toil oil work wonders in dusty environments.

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Final Verdict: A Timeless Trials Weapon

The GAS GAS TXT 125 (2011–2015) isn’t about brute force; it’s about finesse. Whether you’re hopping onto a fallen tree or inching up a granite slab, this bike rewards skill and punishes clumsiness—exactly as a trials machine should. While newer models boast fuel injection and lighter frames, this generation remains a benchmark for accessible, analog trials performance.

For owners looking to refresh their TXT 125, MOTOPARTS.store offers everything from OEM-style replacement parts to performance upgrades. Because even legends deserve a second wind.

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Specifications sheet

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