The 2003-2007 Kawasaki KX 125 is part of Kawasaki’s line of high-performance two-stroke motocross motorcycles, well-regarded for their power-to-weight ratio, agility, and reliability. Here’s a detailed breakdown:

General Overview

• Model Years: 2003-2007
• Category: Motocross / Off-road
• Engine Type: 2-stroke single-cylinder
• Target Audience: Intermediate and advanced riders seeking a lightweight, competitive motocross bike.

Engine and Performance

• Displacement: 124 cc
• Cooling System: Liquid-cooled, ensuring optimal performance during high-stress riding.
• Bore x Stroke: 54.0 mm x 54.5 mm
• Fuel System: Keihin PWK38S carburetor for responsive throttle and efficient fuel delivery.
• Ignition System: CDI (Capacitor Discharge Ignition)
• Power Output: Approximately 35 HP, depending on tuning and modifications.
• Powerband: Known for its aggressive powerband, delivering a strong mid-to-top-end punch.

Drivetrain

• Transmission: 6-speed manual, allowing riders to maximize power delivery across various terrains.
• Clutch: Multi-disc wet clutch for smooth engagement.

Chassis and Suspension

• Frame: High-tensile steel perimeter frame, lightweight yet durable.
• Front Suspension:
  • 2003-2004: 47 mm Kayaba inverted fork with 12.2 inches of travel.
  • 2005-2007: Upgraded Showa inverted forks with improved damping control.
• Rear Suspension: Uni-Trak® linkage system with a fully adjustable Kayaba or Showa shock (depending on year) and 12.2 inches of travel.

Brakes and Wheels

• Front Brakes: Hydraulic disc with a dual-piston caliper.
• Rear Brakes: Hydraulic disc with a single-piston caliper.
• Tires: Off-road motocross tires, with options for customization depending on terrain.

Dimensions and Weight

• Seat Height: Approximately 37.2 inches, suitable for riders with moderate to tall stature.
• Ground Clearance: 13.4 inches, ideal for motocross tracks and off-road conditions.
• Weight: Around 192 lbs (dry), making it lightweight and highly maneuverable.

Features

• Ergonomics: Slim profile and lightweight design for excellent handling and control.
• Handlebars: Adjustable positions to accommodate rider preferences.
• Aesthetics: Aggressive styling with Kawasaki’s signature green color and bold graphics.
• Tank Capacity: 2.1 gallons, sufficient for motocross events and practice sessions.

Notable Updates (2003-2007)

• 2005 Redesign: The KX 125 received significant updates in 2005, including a new frame, revised suspension components, and minor engine refinements for better performance and handling.
• Improved Suspension: Upgraded forks and rear shock for more precise tuning and greater control.
• Weight Reduction: Continuous improvements aimed at reducing weight and improving agility.

Pros

• Lightweight and easy to handle.
• Excellent mid-to-top-end power delivery.
• Durable and reliable for a two-stroke engine.
• Strong aftermarket support for parts and upgrades.

Cons

• Requires frequent maintenance, as expected for a two-stroke motocross bike.
• Limited low-end torque compared to four-strokes.
• Discontinued after 2007, making OEM parts harder to find.

Legacy

• The KX 125 holds a special place in motocross history as a competitive and reliable two-stroke bike, well-suited for riders who favor aggressive and nimble machines.
• It was part of the last generation of two-strokes before the widespread shift to four-stroke bikes in competitive motocross.
• Collectors and enthusiasts often seek out well-maintained or restored KX 125s for their nostalgic and high-revving performance.

If you’re restoring or maintaining one of these bikes, a strong aftermarket community exists, offering everything from OEM replacement parts to performance upgrades. It’s a great bike for two-stroke fans who appreciate the simplicity and excitement of these machines.