Segment:
High-performance two-stroke motocross motorcycle.
Target Audience:
Motocross racers, off-road enthusiasts, and DIY mechanics who own or service the 2007 Yamaha YZ250.
Competitors:
KTM 250 SX, Honda CR250R, Kawasaki KX250, Suzuki RM250.
Performance Focus:
Renowned for its potent two-stroke power delivery and agile handling.
Value Proposition:
Provides essential factory-level information for maintaining and repairing the YZ250, saving time and money on professional servicing.
Coverage:
Complete tear down and rebuild, maintenance, troubleshooting, diagnostics, electrical systems, chassis components, engine internals, suspension, brakes, bodywork.
Manual Type:
Factory Repair Manual / Service Manual
Format:
Digital Download (PDF)
Engine:
Complete engine overhaul, piston, rings, cylinder, crankshaft, connecting rod, bearings, seals, gaskets, lubrication system, cooling system (if applicable, though typically air-cooled for YZ250), exhaust system, carburetor (jetting, cleaning, adjustment).
Transmission:
Gearbox components, clutch assembly, shift mechanism, transmission oil specifications and change intervals.
Suspension:
Front forks (damping, seals, oil, springs), rear shock absorber (rebuild, adjustments, linkage maintenance).
Brakes:
Front and rear brake systems, hydraulic lines, caliper rebuild, master cylinder service, brake fluid specifications, pad replacement, rotor inspection.
Electrical:
Ignition system, lighting (if applicable), wiring diagrams, CDI unit, spark plug specifications, battery maintenance (if applicable for starting system).
Chassis And Bodywork:
Frame inspection, handlebars, footpegs, seat, fuel tank, fenders, plastics, chain and sprockets, wheel bearings, steering head bearings.
Maintenance Procedures:
Routine service, oil changes, filter cleaning/replacement, spark plug inspection/replacement, chain lubrication and adjustment, brake bleeding, general cleaning and inspection.
Repair Procedures:
Complete engine rebuild, transmission disassembly and reassembly, suspension fork and shock servicing, brake system repair, clutch replacement, carburetor overhaul.
Troubleshooting Diagnostics:
Step-by-step guides for diagnosing common performance issues, starting problems, and component failures. Includes symptom analysis.
Technical Specifications:
Torque specifications for all fasteners, engine clearances, fuel mixture settings, suspension settings, and other critical data.
Depth:
Comprehensive from basic maintenance to complete engine and gearbox rebuilds. Suitable for home mechanics and professional technicians.
Engine Type:
Liquid-cooled, 2-stroke, Reed valve, YPVS (Yamaha Power Valve System)
Bore X Stroke:
66.4 mm x 72.0 mm
Compression Ratio:
Typically around 8.6:1 to 10.7:1 depending on specific YPVS setting and test conditions (manual will specify exact for 2007).
Horsepower:
Approx. 50-55 HP (Varies by specific dyno testing and conditions, manual will provide rated output).
Torque:
Significant torque output characteristic of 250cc two-strokes, manual will provide peak torque figures and RPM.
Carburetor:
Keihin PWK38S (likely, manual confirms exact model and jetting).
Fuel Type:
Unleaded gasoline, 90 octane or higher recommended.
Premix:
Yamalube 2R or equivalent high-quality 2-stroke oil (50:1 or 40:1 ratio, manual specifies).
Type:
Constant-mesh 5-speed sequential.
Clutch:
Wet, multiple-disc, cable-actuated.
Optional Transmissions:
N/A (Single standard transmission for this model).
Gear Ratios:
Manual will list specific gear ratios for each of the 5 speeds.
Final Drive:
Chain drive, manual will specify sprocket sizes (e.g., 13T front, 50T rear).
Transmission Oil:
Yamalube 10W-30 or equivalent SAE 80 API GL-4 hypoid gear oil (manual specifies exact type and capacity).
Oil Change:
Transmission oil change every 10-15 hours of operation or annually. Premix fuel usage dictates engine internal cleaning frequency.
Air Filter Cleaning:
Clean air filter after every few rides, or more frequently in dusty conditions.
Spark Plug Inspection:
Inspect spark plug at regular intervals (e.g., every 10-20 hours) for fouling and wear.
Chain And Sprocket Maintenance:
Lubricate and adjust chain every 5-10 hours. Inspect sprockets for wear.
Transmission Fluid:
Yamalube 10W-30 or SAE 80 API GL-4 gear oil (as per manual).
Brake Fluid:
DOT 4 hydraulic brake fluid.
Coolant:
Not applicable (YZ250 is liquid-cooled, but the manual specifies coolant type and mixture ratio).
Common Wear Items:
Piston and rings, clutch plates, brake pads, wheel bearings, chain and sprockets, suspension seals and bushings.
Two Stroke Specific:
Carbon buildup in exhaust port and power valve system requires periodic cleaning. Carburetor jetting sensitivity to altitude and temperature.
