The Yamaha YZ250 is a legendary two-stroke motocross bike, widely regarded as one of the most iconic and competitive bikes in its class. Known for its lightweight handling, explosive power, and race-ready performance, the YZ250 has been a favorite among motocross enthusiasts and racers for decades.

General Overview

• Category: Motocross / Off-road
• Engine Type: Two-stroke single-cylinder
• Production: Since 1974, continuously updated.
• Reputation: One of the most successful and enduring two-stroke motocross bikes in history, recognized for its blend of performance, reliability, and ease of maintenance.

Engine and Performance

• Displacement: 249 cc
• Cooling System: Liquid-cooled (introduced in 1982).
• Bore x Stroke: 66.4 mm x 72.0 mm
• Compression Ratio: 8.9:1 (varies slightly by year).
• Carburetor: Keihin or Mikuni 38 mm (depending on year), offering precise fuel delivery.
• Horsepower: Approximately 46 HP, making it one of the most powerful two-stroke bikes in its class.
• Power Valve: Yamaha Power Valve System (YPVS), introduced in the early 1980s, smooths out power delivery and enhances low- to mid-range torque.
• Powerband: Explosive mid-to-top-end power, with strong performance across the RPM range, thanks to the YPVS.

Drivetrain

• Transmission: 5-speed manual gearbox, optimized for motocross and off-road riding.
• Clutch: Multi-plate wet clutch for consistent engagement.
• Final Drive: Chain drive for durability and ease of maintenance.

Chassis and Suspension

• Frame:
  • Early Years: Steel frame.
  • 2005-Present: Aluminum bilateral beam frame for reduced weight and increased rigidity.
• Front Suspension:
  • KYB 48 mm inverted forks (Speed-Sensitive System or SSS).
  • Fully adjustable for compression and rebound damping.
  • Approximately 12.2 inches of travel.
• Rear Suspension:
  • KYB single shock with linkage.
  • Fully adjustable for preload, compression, and rebound damping.
  • Around 12.4 inches of travel.
• Handling: Known for nimble and precise handling, with excellent stability over rough terrain and jumps.

Brakes and Wheels

• Front Brakes: Single hydraulic disc (270 mm) with a dual-piston caliper for strong stopping power.
• Rear Brakes: Single hydraulic disc (245 mm) with a single-piston caliper.
• Tires: 21-inch front and 19-inch rear, designed for optimal motocross performance.

Dimensions and Weight

• Seat Height: Approximately 38 inches, standard for motocross bikes.
• Ground Clearance: 14 inches, suitable for navigating obstacles on the track or trail.
• Weight:
  • Dry weight: Approximately 227 lbs.
  • Wet weight: Around 231 lbs (ready to ride).
• Fuel Capacity: 2.1 gallons, with a reserve.

Key Updates by Era

1. 1974 (Debut):
   • Yamaha’s first dedicated motocross bike with a two-stroke engine.
   • Air-cooled with drum brakes.
2. 1982:
   • Introduced liquid cooling, enhancing engine reliability and power.
   • Debut of the Yamaha Power Valve System (YPVS) for broader power delivery.
3. 1990s:
   • Refinements to suspension and engine for better track performance.
   • Ergonomic improvements for rider comfort and control.
4. 2005:
   • Major redesign with an aluminum bilateral beam frame for improved handling and reduced weight.
5. 2015:
   • Updated suspension with KYB SSS forks, enhancing damping performance.
   • Modernized bodywork and ergonomics.

Features

• Ergonomics: Slim design for easy rider movement and control during aggressive riding.
• Durability: Yamaha’s engineering ensures longevity, even under extreme conditions.
• Aftermarket Support: Extensive options for performance upgrades and customization.
• Simplicity: Two-stroke design makes it easier to maintain compared to modern four-stroke motocross bikes.

Pros

• Lightweight and nimble, excelling in tight tracks and corners.
• Strong and consistent power delivery, thanks to the YPVS.
• Reliable and durable with a reputation for low maintenance costs.
• High-quality KYB suspension provides excellent handling and comfort.
• Easy to rebuild and modify with abundant aftermarket support.

Cons

• Requires frequent maintenance, including regular top-end rebuilds.
• Vibrations can be noticeable at high RPMs.
• Limited low-end torque compared to modern four-strokes.
• Kickstart only, which may be inconvenient for some riders.

Riding Experience

• The YZ250 offers an exhilarating ride with its explosive power and precise handling.
• Ideal for motocross tracks, it performs exceptionally well in jumps, corners, and high-speed sections.
• Its lightweight and agile design make it a joy to ride in technical terrain, rewarding experienced riders with thrilling performance.

Legacy

• The YZ250 has won countless championships and is considered a legend in motocross and off-road racing.
• Despite the rise of four-stroke bikes, the YZ250 remains a favorite among two-stroke enthusiasts and vintage racers.
• Yamaha’s continuous updates ensure the YZ250 remains relevant, even in the modern motocross world.

If you're considering a Yamaha YZ250, you're investing in a time-tested, race-ready machine that delivers unparalleled excitement and performance. Its legacy as one of the best two-stroke motocross bikes ensures it will always have a dedicated following.