🏷️ Basic Information

Make:

Yamaha

Model:

YZ250

Model Year:

2005

Engine Type:

2-Stroke

Engine Identifier:

YZ250 (5MV)

Product Code Indicator:

YZ250 2005 05

👋 Introduction

Segment:

Motocross / Off-Road Competition

Target User:

Enthusiast riders, mechanics, and racers seeking detailed maintenance and repair information for their YZ250.

Competitors 2005:

KTM 250 SX, Suzuki RM250, Honda CR250R, Kawasaki KX250.

Performance Focus:

This manual is tailored for a high-performance, competition-oriented machine.

Diagnostic Capabilities:

Provides detailed diagnostic procedures for pinpointing mechanical and electrical issues.

Visual Aids:

Includes numerous diagrams, illustrations, and exploded views crucial for understanding complex procedures.

📋 Manual Details

Primary Coverage:

2005 Yamaha YZ250

Secondary Coverage Note:

Compatible with similar years and models (user discretion advised).

Estimated Page Count:

300-400 pages (typical for this model's comprehensive service manual)

Type:

Service Repair Workshop Manual

Language:

English

Format:

Digital (likely PDF, though print option may exist)

📖 Manual Coverage

Engine Mechanical:

Complete disassembly, inspection, and reassembly of the 2-stroke engine, including cylinder, piston, crankshaft, connecting rod, bearings, seals, and more.

Fuel System:

Carburetor (Mikuni VM38) tuning, cleaning, rebuilding, jetting information, fuel tank, fuel lines, and petcock.

Ignition System:

CDI ignition system, stator, coil, spark plug specifications, troubleshooting.

Cooling System:

N/A (Air-cooled engine)

Exhaust System:

Expansion chamber, muffler, and related components' maintenance and repair.

Transmission Drivetrain:

Clutch operation, disassembly, and adjustment; gearbox internal components, lubrication, and shift mechanism.

Suspension Front:

Kayaba (KYB) 46mm USD forks: disassembly, oil change, seal replacement, spring rates, damping adjustments, and general maintenance.

Suspension Rear:

Monocross rear suspension system: shock absorber servicing, linkage maintenance, bearings, and adjustments.

Brakes Front:

Hydraulic disc brake system: caliper servicing, master cylinder, brake pads, fluid type (DOT 4), bleeding procedures, and rotor inspection.

Brakes Rear:

Hydraulic disc brake system: caliper servicing, master cylinder, brake pads, fluid type (DOT 4), bleeding procedures, and rotor inspection.

Wheels Tires:

Hubs, spokes, rims, wheel bearings, tire pressure, and recommended tire sizes.

Electrical System:

Wiring diagrams, lighting (if applicable), kill switch, and basic electrical component troubleshooting.

Frame Chassis:

Frame inspection, steering head bearings, swingarm pivot, and general chassis maintenance.

Bodywork Plastics:

Removal and installation of fenders, seat, fuel tank cover, and side panels.

Routine Maintenance:

Oil changes, filter cleaning/replacement, chain adjustment, spark plug checks, air filter cleaning, brake adjustments.

Troubleshooting:

Diagnostic flowcharts and symptom-based troubleshooting for common issues like starting problems, poor running, and clutch slippage.

Engine Rebuild:

Detailed steps for top-end rebuild (piston, rings, cylinder) and potentially bottom-end (crankshaft, bearings).

Suspension Servicing:

Fork seal replacement, oil level and type specification, shock absorber maintenance.

Brake System Maintenance:

Brake fluid flush and bleed, pad replacement, caliper cleaning.

Carburetor Rebuilding:

Step-by-step instructions for disassembling, cleaning, and reassembling the Mikuni VM38 carburetor, including jetting charts.

Clutch Adjustment And Service:

Cable adjustment, clutch plate inspection and replacement.

Depth:

Comprehensive from basic maintenance to advanced troubleshooting and complete engine/suspension rebuilds.

📊 Manual Specifications

Digital Format:

PDF (typically Searchable and Printable)

Print Quality:

High-resolution scans of original factory manual pages, ensuring clarity of diagrams and text.

Binding Type:

N/A (Digital Format)

Paper Type:

N/A (Digital Format)

⚙️ Engine Specifications

Engine Configuration:

Single-cylinder, liquid-cooled (Note: YZ250 is typically air-cooled, but manual might cover variations or specific components that are liquid-cooled, *correction: YZ250 2005 is AIR-COOLED.*)

Displacement:

249cc

Bore X Stroke:

72.0 mm x 60.0 mm

Compression Ratio:

9.3:1 (Typical, manual will confirm)

Power Valve System:

YPVS (Yamaha Power Valve System)

Horsepower:

Approx. 45-50 HP (at crank, subjective to tuning and specific dyno)

Torque:

Specific figures not typically emphasized for this class, but focus on broad powerband.

Carburetor Model:

Mikuni VM38

Fuel Type:

Unleaded gasoline (91 octane or higher recommended, specific mix with 2-stroke oil for fuel/oil injection if applicable, or premix ratio)

Premix Ratio:

50:1 (Yamalube 2R or equivalent high-quality 2-stroke oil recommended, manual will specify).

🔧 Transmission

Type:

5-speed constant mesh sequential transmission

Option:

N/A (Standard configuration for this model)

Clutch Type:

Wet, multi-plate, cable-actuated

Gear Ratios:

Detailed in manual (e.g., 1st: 2.615, 2nd: 1.867, 3rd: 1.435, 4th: 1.130, 5th: 0.917)

Final Drive:

Chain drive

Transmission Oil Type:

Yamalube SAE 10W-30 API SE class SC or SB (Manual will confirm exact specification and capacity).

📐 Dimensions

Overall Length:

Approx. 2175 mm (85.6 in)

Overall Width:

Approx. 825 mm (32.5 in)

Overall Height:

Approx. 1285 mm (50.6 in)

Seat Height:

Approx. 985 mm (38.8 in)

Wheelbase:

Approx. 1475 mm (58.1 in)

Ground Clearance:

Approx. 335 mm (13.2 in)

Dry Weight:

Approx. 99 kg (218 lbs)

Fuel Tank Capacity:

8.0 L (2.1 US gal)

🛡️ Safety Features

Safety Certification:

Not applicable for off-road competition motorcycles in typical consumer safety rating systems.

Braking System:

Powerful hydraulic disc brakes front and rear for effective stopping power.

Suspension Performance:

Advanced suspension provides stability and control over varied terrain.

Frame Construction:

Durable aluminum frame provides a strong and responsive chassis.

💡 Technology Features

Infotainment System:

N/A (Dedicated motocross competition machine).

Assistance Features:

N/A (Focus is on rider input and mechanical performance).

Connectivity Features:

N/A

🔧 Maintenance

Oil Change Transmission:

Every 10-15 hours of use or annually, whichever comes first. (Manual provides precise recommendation).

Air Filter Cleaning:

After every few rides, especially in dusty conditions. (Manual details method).

Spark Plug Inspection:

Regularly, recommend replacement based on wear. (Manual specifies type and gap).

Chain Lubrication Adjustment:

Before every ride and adjust as needed. (Manual provides slack specification).

Suspension Fork Oil Change:

Every 20-30 hours of use or annually. (Manual specifies oil type and level).

Transmission Oil:

Yamalube SAE 10W-30 API SE class SC or SB (Confirm in manual for exact spec).

Brake Fluid:

DOT 4

Fork Oil:

Yamalube Fork Oil G10 or equivalent (Manual specifies viscosity and volume).

Common Wear Items:

Piston rings, clutch plates, wheel bearings, suspension seals, and brake pads are common wear items for this model.

Carburetor Tuning:

Sensitivity to altitude and temperature changes requiring periodic jetting adjustments is common for 2-stroke motocross bikes.

Power Valve Maintenance:

The YPVS system requires periodic cleaning to prevent carbon buildup and ensure proper operation.

📚 Vehicle History

Yamaha Motorcycles:

Yamaha has a long-standing reputation for performance and innovation in motocross and off-road racing since the 1970s.

Yz Lineage:

The YZ250 is a direct descendant of Yamaha's highly successful YZ racing lineage, continuously refined for performance.

2005 Updates:

The 2005 model likely received refinements based on previous racing feedback, potentially including suspension tuning or minor engine tweaks. This manual will detail the specific features of the '05 iteration.

Manufacturing Origin:

Japan (typical for Yamaha at this time)

🏆 Awards & Recognition

Motocross Legacy:

The YZ250 platform has a rich history of success in professional motocross and supercross championships.

Performance Reviews:

Consistently praised in period reviews for its potent engine, agile handling, and robust suspension.