Category:
Motocross Competition
Target Audience:
Motocross racers, off-road enthusiasts, mechanics, and Yamaha owners seeking detailed technical information.
Key Competitors 2001:
Honda CRF450R, Kawasaki KX450F, Suzuki RM450Z (though 4-stroke market was nascent).
Vehicle Highlights:
Powerful 4-stroke engine, advanced suspension, lightweight chassis, and competitive motocross performance.
Manual Value Proposition:
Provides essential information for maintaining, troubleshooting, and repairing the YZ426F, ensuring optimal performance and longevity.
Engine:
Complete engine disassembly, inspection, repair, and reassembly. Includes top-end, bottom-end, lubrication, cooling, and valve train.
Transmission:
Detailed procedures for transmission removal, disassembly, inspection, assembly, and installation. Covers gear selection, clutch operation, and shift linkage.
Chassis:
Front suspension (forks), rear suspension (shock absorber, linkages), steering system, frame, and subframe.
Brakes:
Front and rear hydraulic brake systems, including caliper disassembly, piston replacement, brake fluid bleeding, and pad/rotor inspection.
Electrical System:
Ignition system, lighting, battery, wiring diagrams, component testing, and troubleshooting for electrical faults.
Fuel System:
Carburetor (Mikuni) specifications, disassembly, cleaning, adjustment, and jetting. Fuel tank and petcock.
Exhaust System:
Exhaust pipe and silencer inspection, removal, and installation.
Wheels And Tires:
Wheel bearing inspection and replacement, spoke tensioning, and tire changing procedures.
Maintenance Procedures:
Oil changes, filter replacement, chain adjustment, spark plug service, air filter cleaning, valve clearance checks, and general lubrication.
Troubleshooting:
Diagnostic flowcharts and common problem identification for engine performance, electrical issues, and chassis components.
Repair Procedures:
Step-by-step instructions for rebuilding major components, replacing worn parts, and correcting specific malfunctions.
Specifications And Measurements:
Torque values for all fasteners, critical clearances, fluid capacities, and performance data.
Parts Identification:
Detailed parts diagrams with OEM part numbers for ordering replacement components.
Depth Of Coverage:
Comprehensive, covering routine maintenance to full engine and transmission rebuilds, including electrical diagnostics and suspension tuning.
Engine Type:
Four-stroke, liquid-cooled, DOHC, 5-valve
Bore X Stroke:
95.0 mm x 60.0 mm
Compression Ratio:
12.6:1
Carburetor:
Mikuni TM40SS, Flat-slide, w/TPS
Valve Actuation:
DOHC, 5 valves per cylinder (3 intake, 2 exhaust)
Horsepower Estimate:
Approximately 45-50 hp (at crank, varies with tuning and conditions)
Torque Estimate:
Approximately 30-34 lb-ft (at crank, varies with tuning and conditions)
Fuel Type:
Unleaded gasoline, minimum 91 octane (RON+MON)/2
Fuel Tank Capacity:
2.4 gallons (9.0 Liters)
Safety Certification:
N/A (Off-road competition vehicle)
Braking System Type:
Hydraulic disc brakes, front and rear
Suspension Design:
Upside-down telescopic front forks, Monocross rear suspension with adjustable shock.
Frame Construction:
Aluminum alloy semi-double cradle frame
Engine Oil Change:
Every 5-10 hours of operation (depending on riding conditions).
Air Filter Cleaning:
After every few rides, or more frequently in dusty conditions.
Spark Plug Service:
Check and clean every 10-15 hours; replace as needed.
Valve Clearance Check:
Every 20-30 hours of operation.
Chain Lubrication And Adjustment:
Regularly, as needed.
Engine Oil Type:
Yamalube 4 (or equivalent) SAE 10W-40, API SG or higher.
Engine Oil Capacity:
1.10 US qt (1.05 L) without filter change; 1.20 US qt (1.15 L) with filter change.
Coolant Type:
High-quality, permanent type antifreeze coolant with low silicate content, mixed 50/50 with distilled water.
Brake Fluid Type:
DOT 3 or DOT 4 brake fluid.
Transmission Oil Type:
Yamaha Gear Oil GL-4 SAE 80W (or equivalent).
Transmission Oil Capacity:
0.75 US qt (0.70 L).
Common Wear Items:
Piston rings, valve guides, clutch plates, wheel bearings, steering head bearings, and suspension seals.
Carburetor Tuning:
Can be sensitive to altitude and temperature changes, often requiring jetting adjustments for optimal performance.
Decarbonization:
Periodic decarbonization of the combustion chamber and exhaust port is recommended to maintain power.
Yamaha Motorcycle Division:
Yamaha Motor Corporation is a global leader in powersports, with a long history of innovation in motorcycle design and racing.
Predecessor:
YZ400F (introduced in 1998, marking Yamaha's return to 4-stroke motocross).
Advancement From Yz400F:
The YZ426F offered increased displacement, improved power delivery, and chassis refinements over the YZ400F.
Production Period:
Produced from 2000 to 2002, before being succeeded by the YZ450F.
Racing Success:
The YZ426F platform was highly competitive in AMA Supercross and Motocross, contributing to Yamaha's racing heritage.
Review Sentiment:
Generally well-received for its powerful engine and capable chassis, considered a benchmark in early 4-stroke motocross bikes.
Emissions Standards:
N/A (Off-road competition vehicle, not typically subject to road-legal emissions standards).
