2001–2002 Yamaha YZ426F Maintenance & Service Manual (P/N 5JG-28199-81)

• Yamaha YZ426F(N)/LC Owner’s Service Manual, cover reference 5JG-28199-81, supplied as a 623-page PDF with English, French, and German text.
• Engine repair covers cylinder-head service, camshaft timing, engine removal, crankcase separation, and internal transmission, shift-cam, and shift-fork work.
• Keihin FCR MX39 carburetor coverage includes disassembly, float-height adjustment, accelerator-pump inspection, and hot- and cold-start circuits.
• Front and rear brake procedures cover caliper and master-cylinder rebuilding, hydraulic bleeding, and brake-disc inspection.
• Chassis repair extends to front-fork disassembly, steering-head bearing replacement, and swingarm and Monocross suspension-linkage service.
• Map-controlled CDI and TPS diagnostics combine a wiring diagram with ignition and throttle-position-sensor inspection flowcharts.

The owner sections explain controls, starting, break-in, and routine maintenance. The repair sections are suited to mechanics familiar with precision measurement and the specified Yamaha service tools.

Model Coverage and Manual Layout

The factory specifications identify these regional versions:

European specifications distinguish final gearing, fork settings, and an unequal-pitch rear shock spring. These regional entries matter when selecting replacement springs or checking the original setup.

Organized into seven sections, the manual moves from machine identification and pre-ride checks into engine and chassis repair, electrical diagnosis, and tuning. Mechanical coverage centers on the liquid-cooled, 426 cc DOHC single with dry-sump lubrication, manual decompression, and kick starting.

Engine Repair and Factory Specifications

Valve service goes beyond checking intake and exhaust clearance. Separate pad-selection tables support clearance adjustment, while the cylinder-head section covers valve sealing, guide replacement, seat reconditioning, and color-code matching of valve lifters to cylinder heads.

Camshaft service notes explain how uneven cap-bolt tightening can damage the cylinder head, camshafts, and caps.

The wet multi-plate clutch section details the damper spring, friction-plate arrangement, and pushrod release mechanism. Inspection and assembly procedures also cover the five-speed constant-mesh gearbox and balancer-gear indexing.

Oil-pump rotor inspection and water-pump shaft, bearing, and seal replacement support lubrication and cooling-system repairs. Radiator-cap and cooling-system pressure tests help investigate coolant loss. Lubrication diagrams trace oil delivery to the camshafts, crankshaft, and transmission.

Reference tables provide engine and chassis tightening torques, fluid capacities, piston-to-cylinder clearances, and component wear limits. General specifications also document frame construction and steering geometry.

Suspension Service and Repair Limits

The Front Fork Disassembly exploded view identifies the seals, bushings, base valve, and damper rod. Related procedures cover oil filling, air bleeding, and oil-level adjustment. Assembly cautions address internal-valve damage caused by an uncontrolled damper-rod drop into the fork tube.

Swingarm and linkage work includes bearing, collar, bushing, and seal inspection, with installation-depth specifications and lubrication points.

Rear shock coverage includes removal, spring replacement, mounting-bearing service, preload adjustment, and damping adjustments. It does not include internal damper or nitrogen-reservoir overhaul; leaking or damaged damper units are addressed through assembly replacement. Yamaha specifically recommends dealer maintenance for the front fork.

Electrical Tests and Race Setup

Electrical checks cover ignition-coil primary and secondary resistance, magneto pickup and source coils, engine-stop-button operation, and neutral-switch continuity. TPS coverage includes resistance and input-voltage testing, plus replacement and adjustment procedures. Wiring color codes and cable-routing diagrams support fault tracing and reassembly.

The tuning chapter relates carburetor jet and needle selection to throttle opening, atmospheric conditions, and running symptoms. Suspension-setting charts address bottoming, poor grip, stiffness, and instability. Sprocket-selection guidance and spring-option tables provide part numbers and identification markings for setup changes.

Yamaha Special Tools

The tool list identifies equipment such as the crankcase separator YU-1135-A / 90890-01135 and fork seal driver YM-01442 / 90890-01442, with descriptions of their uses. It distinguishes U.S. and Canadian tool numbers from those used in other markets.

For hands-on work, follow the complete manual’s procedures and safety precautions, particularly for hot pressurized coolant and the nitrogen-charged rear shock.