2003 GAS GAS Supermoto EC 125 / 200 / 250 / 300 Service Manual

EC series enduro competition motorcycles technical service documentation with maintenance schedules, ignition timing CDI adjustment, and carburetor tuning specifications

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Document Details

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Document Number / Seller:
23936 / Jennifer Cooper
File Size:
9.43 MB
File Type:
PDF
Language:
English
Pages:
50+
Printable:
Yes
Category:
Motorbike
Last updated / verified
Jan 25, 2026

Models Covered & Key Technical Specifications

GAS GAS Supermoto EC 125, EC 200, EC 250, EC 300 — 2003 Precision Engineering Repository | Supermoto Series Packet.

  • Factory Assembly Gap: For optimal ignition performance, 1 mm APMS defines the ignition timing specification Mapping.
  • Calibrated Displacement Data: The engine displacement achieves 124 cc (125 cc), 199.4 cc (200 cc), 249.3 cc (250 cc), and 294.7 cc (300 cc) respectively Configuration.
  • Key Load Capacity: Rear axle nut — determines the wheel retention force at 98 N·m (70 ft-lbs) Benchmarks.
  • Primary Thermal Envelope: The cooling system requires 1.1 L total coolant capacity for aluminum engine protection Range.
  • General Size Parameters: Fuel tank capacity sets the operational range at 9.5 L (2.5 US gallons) Sequences.
  • Integral Running Clearance: Drive chain slack reaches 30–50 mm (1.2–2.0 in) between the chain and swing arm Baseline.

Professional Workshop Service Manual & Technical Specifications

Practical Workshop Manual: Motorcycle GASGAS Supermoto EC 125, EC 200, EC 250, EC 300 - Comprehensive Service & Repair Manual, 2003 edition Reference-Archive

Engine-Type: GAS GAS EC 125 (2003), GAS GAS EC 200 (2003), GAS GAS EC 250 (2003), GAS GAS EC 300 (2003) // Series-Validation: Two-stroke Competition Enduro / Multi-displacement Powertrain Logic // Technical-Scope: Liquid-cooled CDI ignition, 6-speed transmission, WP/Marzocchi/Öhlins suspension systems.

Documentation Element Scope Reference
Engine Specifications Bore/stroke dimensions, displacement volumes for all models Pages 67-68
Transmission Systems Gear ratios, clutch type, chain drive configuration Pages 67-68
Chassis Architecture Suspension stroke, brake disc sizing, fuel capacity Pages 68-69

Accurately requiring systematic maintenance protocols, the manual encompasses engine systems, transmission operation, and chassis management. The document addresses fuel mixing ratios for 2-stroke lubrication, cooling system maintenance including radiator care and antifreeze specifications, and spark plug evaluation procedures. Carburetor tuning is thoroughly documented with standard settings, correction factors for altitude and temperature conditions, and jet needle positioning guidance. Ignition timing references are provided for CDI system verification, and transmission oil specifications including capacity and change intervals are detailed.

Service intervals are documented for clutch friction plate inspection, drive chain slack adjustment, and brake disc wear assessment. The manual covers front fork oil level management for WP, Marzocchi, and Öhlins suspension variants, with rebound and compression dampening adjustment click ranges. Rear suspension spring preload adjustment procedures and shock absorber oil viscosity recommendations are included. Component locations are identified for fuel tank fill cap, air cleaner assembly, carburetor positioning, and brake fluid reservoirs across all four displacement variants.

Drivetrain specifications are addressed in sections covering chain guide wear inspection, sprocket tooth condition evaluation, and master link installation orientation. The document includes torque specifications for cylinder head fasteners, engine drain plugs, front axle retention, and rear axle nut security to ensure proper component alignment retention. Bolt and nut tightening reference data spans engine, chassis, and suspension mounting points across 33 critical fastener locations.

Reassembly procedures are specified for silencer packing replacement, including inner pipe rivet removal and new packing installation. Handlebar position adjustment, brake lever play configuration, and rear brake pedal position setup are documented with numerical clearance targets. Steering stem locknut adjustment methodology is provided alongside front fork upper and lower clamp bolt torque specifications, with step-by-step assembly sequence references for fork spring installation and suspension cap installation.

System Category Documented Content Source Section
Fuel System Octane rating requirements, oil mixing ratios, fuel tank capacity Pages 71-72
Cooling System Radiator fin inspection, antifreeze mixture ratios, coolant drain plug procedures Pages 78-80
Electrical CDI ignition timing reference marks, spark plug gap specifications Pages 78, 81
Drive System Chain slack measurement (30-50 mm), sprocket wear limits, lubrication intervals Pages 86-88
Brake Systems Disc diameter specifications, pad thickness minimum (1 mm), fluid type (DOT 3/4) Pages 89-90

The manual documents torque specifications for the front brake caliper mounting bolts, disc plate fastening screws, and engine suspension mounting points to ensure proper structural integrity. Handlebar clamp bolt tension and steering head nut specifications are recorded with foot-pound equivalents for international reference. Suspension tuning guidance includes fork oil level adjustment methodology and rear shock preload range documentation, with settings calibrated for rider weight categories and track condition adaptation.

Troubleshooting reference material is organized by engine operation symptoms, transmission engagement issues, suspension performance complaints, and brake system effectiveness. The document provides diagnostic pathways for spark plug condition assessment (ceramic insulator color evaluation), fuel system obstruction identification, and cooling system pressure maintenance. Storage preparation sequences and post-storage reactivation checklists are detailed with lubrication point references and seasonal maintenance considerations for extended idle periods.

FAQ

Reference the **specified** torque requirement for the rear axle nut? keyboard_arrow_down

98 N·m (70 ft-lbs) is the required tightening torque for the rear axle nut to ensure wheel security and safe operation.

What are the **essential** spark plug gap specifications for optimal ignition? keyboard_arrow_down

0.7-0.8 mm gap is the standard specification, adjusted by bending the outer electrode if the measurement is incorrect.

Specify the **correct** transmission oil capacity for the EC models? keyboard_arrow_down

1800 cc total capacity is required; EC 200/250/300 use 900 cc per oil change and EC 125 uses 650 cc, as detailed in page 42 maintenance procedures.

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Reviews (5)

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This manual is a must-have for maintaining my EC 250. The troubleshooting section saved me time and money!
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As a new rider, this manual was incredibly helpful. The download process was seamless and I received the link quickly.
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The engine tuning procedures are well explained and easy to implement. Downloading was a breeze!
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This manual covers everything you need to know. I was pleasantly surprised by the quick response from customer support!
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I appreciated the detailed maintenance schedules. The email support was also very responsive when I had a question.