🏷️ Basic Information

Make:

Yamaha

Model:

YZ250

Year:

1994

Vehicle Type:

Motorcycle

Segment:

Motocross / Off-Road

Engine Code:

Likely 5CU (for 1994 YZ250, though not explicitly stated in product info)

👋 Introduction

Positioning:

The 1994 Yamaha YZ250 was a highly competitive motocross machine of its era, known for its potent two-stroke power and aggressive handling. This manual serves enthusiasts and mechanics looking to maintain or restore this iconic dirt bike.

Competitors Of Era:

Honda CR250R, Suzuki RM250, Kawasaki KX250

Value Proposition:

Provides factory-level accuracy for repairs and maintenance, enabling owners to keep their YZ250 performing at its peak or to undertake full restorations. Crucial for DIY mechanics and those wanting to understand the bike's intricate workings.

📋 Manual Details

Engine:

Complete teardown and rebuild, internal components, cooling, lubrication

Transmission:

Clutch, gearbox, shift mechanism

Chassis:

Frame, suspension (front and rear), steering, wheels, brakes

Electrical:

Ignition system, lighting, wiring diagrams, battery

Fuel System:

Carburetor tuning, fuel tank, fuel lines

Bodywork:

Plastics, seat, graphics

Maintenance:

Routine service, lubrication points, fluid changes, adjustments

Troubleshooting:

Diagnostic procedures, common problems and solutions

Total Pages:

263

Type:

Factory Service Manual / Repair Manual

Language:

English

Format:

Digital Download (Implied PDF)

Navigation:

Clickable chapters

📖 Manual Coverage

Engine Mechanical:

Cylinder, piston, crankshaft, connecting rod, bearings, seals, gaskets, valve timing (if applicable, though 2-stroke is simpler), power valve system

Ignition System:

CDI unit, stator, ignition coil, spark plug, timing specifications

Fuel And Carburetion:

Mikuni VM carburetor specifications, jetting, float height, needle settings, air screw, pilot screw adjustments

Cooling System:

Liquid-cooled system, radiator, hoses, water pump, coolant type

Transmission And Drivetrain:

Gear ratios, clutch operation, clutch friction plates, pressure plates, springs, clutch lever adjustment, final drive chain maintenance

Suspension System:

Front forks (KYB or similar), rear shock absorber (Monoshock, likely with adjustable preload and damping), seal replacement, oil levels, damping adjustments

Braking System:

Front and rear hydraulic disc brakes, brake pad replacement, fluid type (DOT 4), bleeding procedure, caliper service

Electrical System:

Wiring diagrams, component testing (lights, horn, kill switch), stator output checks

Engine Rebuild:

Complete engine disassembly, cleaning, inspection of all internal components, reassembly with specified torque values and clearances

Carburetor Service:

Disassembly, cleaning, inspection, and reassembly of the carburetor for optimal performance and fuel delivery

Suspension Overhaul:

Fork seal replacement, fork oil change, shock absorber service, linkage maintenance

Brake System Maintenance:

Brake fluid flush and replacement, pad inspection and replacement, caliper piston service

Clutch Adjustment And Service:

Cable adjustment, clutch plate inspection and replacement, spring tension checks

Engine Troubleshooting:

Diagnosis of common issues like poor starting, loss of power, overheating, and running problems

Electrical Diagnostics:

Testing of ignition system components, lighting circuits, and troubleshooting of electrical faults using wiring diagrams

Torque Specifications:

Precise torque values for critical fasteners throughout the motorcycle

Maintenance Schedules:

Recommended service intervals for various components and systems

Depth:

Comprehensive - Covers basic maintenance to complete engine and chassis overhauls, including detailed troubleshooting guides and factory specifications.

Illustrations:

Numerous pictures and detailed part diagrams

📊 Manual Specifications

Format:

Digital (likely PDF)

Searchability:

High (typical for factory digital manuals, allowing keyword searches)

Printability:

Yes (designed for printing specific sections or the entire manual)

Quality:

Excellent (Factory original quality for diagrams and text)

Binding:

N/A (Digital Format)

Paper:

N/A (Digital Format)

⚙️ Engine Specifications

Engine Type:

2-stroke, Liquid-cooled

Displacement:

249 cc

Bore X Stroke:

68.0 mm x 68.5 mm

Compression Ratio:

8.8:1 (approximate, manual will confirm)

Power Valve System:

Yamaha Power Valve System (YPVS)

Horsepower:

Approximately 45-50 HP (factory figures vary, manual will have specific dyno data or estimates)

Torque:

Approximate 30-33 lb-ft (factory figures vary, manual will have specific data)

Carburetor Model:

Mikuni VM38SS

Fuel Type:

Unleaded gasoline, minimum 91 octane (RON + MON)/2, mixed with 2-stroke oil

Oil Mix Ratio:

50:1 (verify with manual for specific oil)

🔧 Transmission

Type:

5-speed constant mesh

Clutch Type:

Wet, multi-disc

Gear Ratios:

Specific ratios detailed in manual for each gear (e.g., 1st: 2.615, 2nd: 1.938, 3rd: 1.471, 4th: 1.182, 5th: 1.000)

Final Drive:

Chain drive

Transmission Oil Type:

Yamaha Gear Oil (or equivalent 80W/90 API GL-4, manual will specify exact type and capacity)

📐 Dimensions

Length:

Approx. 2145 mm (84.4 in)

Width:

Approx. 820 mm (32.3 in)

Height:

Approx. 1265 mm (49.8 in)

Wheelbase:

Approx. 1465 mm (57.7 in)

Dry Weight:

Approx. 98 kg (216 lbs)

Wet Weight:

Approx. 105 kg (231 lbs) (with fluids, without fuel)

Fuel Capacity:

9.5 L (2.5 US gal)

Coolant Capacity:

0.6 L (0.63 US qt)

🛡️ Safety Features

Crash Test Data:

N/A (Not applicable to off-road motorcycles)

Braking System:

Hydraulic disc brakes front and rear for effective stopping power.

Suspension:

Long-travel, adjustable suspension (front forks and rear monoshock) for control over rough terrain.

Frame Construction:

Durable steel frame designed for off-road stress.

Handlebar Design:

Standard motocross handlebar with reinforced crossbar for rider control and impact absorption.

💡 Technology Features

Infotainment Systems:

N/A (No infotainment or electronic rider aids on this model)

Rider Aids:

N/A (No electronic rider aids)

Connectivity Features:

N/A (No connectivity features)

🔧 Maintenance

Oil Change Transmission:

Every 10-15 hours of riding or annually (check manual for specifics based on usage)

Air Filter Cleaning:

After every few rides, or more frequently in dusty conditions. Manual details cleaning and re-oiling procedures.

Spark Plug Inspection:

Every 10-20 hours of riding. Manual specifies correct type and gap.

Chain Lubrication And Adjustment:

Before every ride, and tension check/adjustment every 5-10 hours.

Top End Rebuild:

Typically every 40-60 hours of aggressive riding (piston and rings). Manual provides wear limits and replacement procedures.

Full Engine Rebuild:

As needed, based on mileage or performance degradation. Manual covers crank bearings, seals, and cylinder.

Transmission Oil:

Yamaha Gear Oil (or equivalent 80W/90 API GL-4, manual will confirm exact spec and capacity)

Coolant Type:

Permanent type coolant (ethylene glycol based), pre-mixed 50/50 with distilled water. Manual will specify exact blend and capacity.

Brake Fluid:

DOT 4 Hydraulic Brake Fluid (manual will confirm)

Fork Oil:

Yamaha Fork Oil G10 or equivalent (manual will specify viscosity and capacity per fork leg)

2 Stroke Oil:

High-quality synthetic blend 2-stroke oil specifically for air-cooled or liquid-cooled racing engines. Manual recommends Yamaha's own or equivalent.

Power Valve Sticking:

Common in 2-stroke engines due to carbon buildup. Manual details inspection and cleaning procedures.

Clutch Wear:

Friction plates can wear over time, leading to clutch slip. Manual provides inspection and replacement guide.

Suspension Seals:

Fork seals and shock seals can degrade, leading to leaks. Manual covers replacement procedures.

Carburetor Jetting Changes:

Sensitivity to altitude and temperature; requires proper jetting for optimal performance. Manual provides comprehensive jetting charts and tuning advice.

📚 Vehicle History

Yamaha Motorcycles:

Yamaha has a long and storied history in motorcycle racing, particularly in motocross, with decades of innovation and championship wins. The YZ line is a cornerstone of their off-road performance heritage.

Yz250 Line:

The YZ250 has been a dominant force in motocross since its inception. The 1994 model represents a refinement of the design, benefiting from years of development and racing feedback, featuring advancements in suspension, engine tuning, and chassis dynamics.

Manufacturing Location:

Primarily Japan (Iwata, Shizuoka)

Production Period:

The YZ250 has been in continuous production for many years, with the 1994 model being part of the highly competitive mid-90s era.

🏆 Awards & Recognition

Motocross Championships:

Yamaha YZ models have consistently been contenders and winners in professional motocross and supercross championships across various classes. The 1994 YZ250 was a factory race bike platform that saw success.

Magazine Reviews Era:

Highly rated by contemporary motocross publications for its powerful engine and responsive chassis. Often lauded for its performance relative to its competitors.