Yamaha YZ426F(N)/LC 2001–2002 Owner’s Service Manual (P/N 5JG-28199-81)

The Yamaha YZ426F(N)/LC Owner’s Service Manual, P/N 5JG-28199-81, combines operating guidance with maintenance, repair, and race setup. Its seven chapters cover the regional versions identified in the model box above.

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Search and diagram detail: Embedded PDF text supports searches across the manual. PDF bookmarks open contents pages rather than individual chapters. Small wiring labels are readable when enlarged.

One printable 623-page PDF contains English, French, and German text. The total includes the front and back covers, five memo pages, and one blank page.

Engine Teardown, Chassis Service, and CDI/TPS Testing

These are selected areas of coverage, rather than a full contents list. Other topics include cleaning and storage, plus exhaust-pipe and silencer removal.

• Engine repair: Cylinder-head service, valve-clearance adjustment, camshaft timing, cylinder and piston inspection, engine removal, and crankcase separation.

• Clutch and transmission: Wet-clutch disassembly, internal gearbox inspection and assembly, shift-cam and shift-fork service, and balancer-gear indexing.

• Carburetor service: Keihin FCR MX39 disassembly, float-height adjustment, accelerator-pump inspection, and hot- and cold-start circuits.

• Brakes and wheels: Front and rear caliper and master-cylinder rebuilding, hydraulic bleeding, brake-disc inspection, and wheel-bearing replacement.

• Steering and suspension: Front-fork disassembly, steering-head bearing replacement, and swingarm and Monocross suspension-linkage service.

• Electrical diagnosis: Map-controlled CDI and TPS testing, with a wiring diagram and separate ignition-system 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.

Regional Specifications and Race Setup

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. General specifications also document frame construction and steering geometry.

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.

Cylinder Head and Internal Engine Work

Step-by-step procedures cover valve sealing checks, guide replacement, and seat reconditioning. A matching chart pairs valve-lifter and cylinder-head paint codes.

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

The clutch section details the damper spring, friction-plate arrangement, and pushrod release mechanism. Gearbox inspection extends to gear dogs and shift-fork grooves, with checks of shifting operation during assembly. Manual-decompression adjustment is covered separately.

Dry-Sump Lubrication and Cooling Repairs

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.

The 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.

Fork Service and Rear Shock Limits

The Front Fork Disassembly exploded view identifies seals, bushings, the 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. Internal damper and nitrogen-reservoir overhaul are outside its scope; leaking or damaged damper units are addressed through assembly replacement. Yamaha specifically recommends dealer maintenance for the front fork.

Ignition Fault Tracing and TPS Adjustment

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 the Cable Routing Diagram support fault tracing and reassembly. The ignition inspection flowchart links a no-spark complaint to component checks before CDI-unit replacement.

Yamaha Special Tools

The tool list identifies 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.

Preview: Valve Clearances and Clutch Wear Limits

Cold valve-clearance specifications are 0.10–0.15 mm for the intake valves and 0.20–0.25 mm for the exhaust valves. Separate pad-selection tables relate measured clearance to replacement pad thickness.

Clutch friction plates have a standard thickness of 2.9–3.1 mm and a 2.7 mm service limit. The inspection section also covers clutch-plate warpage.