The Yamaha YZ 250 is one of the most iconic motocross bikes in history, revered for its powerful two-stroke engine, lightweight handling, and durability. Known as a benchmark in the two-stroke motocross world, the YZ 250 has remained a favorite among racers, enthusiasts, and off-road riders since its debut.

General Overview

• Category: Motocross / Off-road
• Production: Continuously produced since 1974.
• Engine Type: Two-stroke single-cylinder
• Reputation: Known for its strong power, agile handling, and reliability, the YZ 250 is widely considered one of the best two-stroke bikes ever made.

Engine and Performance

• Displacement: 249 cc
• Cooling System: Liquid-cooled (introduced in 1982) for consistent performance.
• Bore x Stroke: 66.4 mm x 72.0 mm
• Compression Ratio: Approximately 8.9:1 (varies slightly by year).
• Carburetor: Keihin or Mikuni (38 mm, depending on model year) for precise fuel delivery.
• Horsepower: Approximately 46 HP, making it one of the most powerful two-stroke 250 cc motocross bikes.
• Power Valve: Yamaha Power Valve System (YPVS) introduced in the early 1980s, providing smoother transitions between low, mid, and high RPM power.
• Powerband: Known for its explosive mid-to-top-end power, while the YPVS broadens usability in lower RPMs.

Drivetrain

• Transmission: 5-speed manual gearbox for precise control and versatility.
• Clutch: Multi-plate wet clutch for smooth and reliable engagement.
• Final Drive: Chain drive, standard for motocross bikes.

Chassis and Suspension

• Frame:
  • Early Models: Steel frame.
  • 2005-Present: Aluminum twin-spar frame for reduced weight and increased rigidity.
• Front Suspension:
  • Early models: Conventional telescopic forks.
  • Modern models: KYB Speed-Sensitive System (SSS) 48 mm inverted forks.
  • Fully adjustable for compression and rebound damping.
  • Travel: Approximately 11.8 inches.
• Rear Suspension:
  • Yamaha’s Monocross system with KYB shock.
  • Fully adjustable for preload, compression, and rebound damping.
  • Travel: Around 12.4 inches.
• Handling: Lightweight and agile, excelling in tight tracks and jumps.

Brakes and Wheels

• Front Brakes: Single hydraulic disc brake (dual-piston caliper).
• Rear Brakes: Single hydraulic disc brake (single-piston caliper).
• Tires: 21-inch front and 19-inch rear, designed for motocross and off-road terrains.

Dimensions and Weight

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

Key Updates by Era

1. 1970s:
   • Debuted in 1974 as Yamaha's first dedicated motocross bike.
   • Air-cooled engine with a steel frame and drum brakes.
2. 1982:
   • Transitioned to liquid cooling, significantly improving performance and reliability.
   • Introduction of the YPVS for smoother power delivery.
3. 1990s:
   • Refinements to suspension and engine for competitive racing.
   • Updated ergonomics and improved weight distribution.
4. 2005:
   • Major redesign with an aluminum twin-spar frame, reducing weight and improving rigidity.
   • Updated suspension for better handling.
5. 2015:
   • Further suspension refinements with KYB SSS forks for superior damping.
   • New bodywork and modernized ergonomics.

Features

• Durability: Yamaha’s reputation for reliability is evident in the YZ 250, which can handle rigorous motocross conditions with proper maintenance.
• Ergonomics: Slim profile for easy rider movement and control.
• Aftermarket Support: Extensive, with countless options for performance upgrades, replacement parts, and customizations.
• Versatility: While designed for motocross, it is also widely used for off-road riding, desert racing, and even hill climbing.

Pros

• Powerful and reliable two-stroke engine.
• Lightweight and nimble, offering excellent handling on tight tracks.
• Proven suspension with class-leading KYB SSS forks.
• Durable components designed to withstand heavy use.
• Easy to maintain compared to modern four-stroke motocross bikes.
• Long production history ensures ample parts availability and aftermarket support.

Cons

• Requires frequent maintenance, especially top-end rebuilds, due to the two-stroke engine.
• Vibrations can be noticeable, especially at high RPMs.
• Limited low-end torque compared to four-stroke competitors.
• Kickstart only, which can be a drawback for some riders.

Riding Experience

• The YZ 250 is a thrilling machine, delivering exhilarating power and precise handling.
• It excels in motocross racing, with quick acceleration and strong performance in jumps, corners, and straights.
• Its lightweight design and nimble handling make it forgiving and fun for intermediate and advanced riders.

Legacy

• The Yamaha YZ 250 remains one of the most iconic and respected two-stroke motocross bikes ever made.
• Its longevity in production speaks to its popularity and effectiveness in the motocross and off-road communities.
• Even in the modern era of four-stroke dominance, the YZ 250 continues to have a loyal following and is a common choice for riders seeking the simplicity and excitement of two-stroke power.

If you’re considering a Yamaha YZ 250, you’re investing in a legendary motocross machine with a proven track record. Whether for racing, recreational riding, or vintage competition, the YZ 250 delivers thrilling performance and exceptional durability.