2004 Yamaha YZ85(T) / YZ85LW(T) Owner's Service Manual (P/N 5PA-28199-83)

Yamaha's Owner's Service Manual covers the 2004 YZ85(T) and YZ85LW(T), including the standard and Large Wheel motocross configurations. This is publication 5PA-28199-83, first edition, April 2004.

• Engine and transmission: Engine removal, crankcase separation, crankshaft and piston inspection, clutch friction-plate replacement, and service of the shift cam and shift forks.

• Fuel and cooling systems: PWK28 Keihin carburetor disassembly, reed-valve inspection, radiator-cap and cooling-system pressure tests, and water-pump repair.

• Brakes and chassis: Hydraulic brake bleeding, caliper and master-cylinder service, wheel-bearing replacement, steering-head inspection, and swingarm linkage service.

• Suspension: Telescopic front-fork rebuilding with oil-seal replacement, rear-shock removal and spring replacement, and model-specific preload and damping adjustments.

• Electrical diagnosis: CDI magneto service, ignition-timing checks, a wiring diagram, and a no-spark inspection chart with component resistance tests.

• Maintenance and tuning: Race-based service schedules, pre-operation checks, fuel mixtures and oil grades, carburetor setting charts, and suspension symptom charts.

The owner sections cover operation and basic maintenance; the repair chapters are suited to mechanics with measuring equipment and the specified service tools.

Engine, Clutch, and Transmission Repair

The engine chapter combines exploded assembly views with job instruction charts, inspection limits, and component torque specifications. Coverage extends to crankshaft bearings and seals, primary gears, the kick shaft and shift shaft, and transmission gear inspection and reassembly. Sectional illustrations clarify details such as circlip orientation.

Piston matching: A cylinder-mark and color-coded piston selection chart helps identify the correct piston grade before ordering replacement parts. Cylinder-bore, piston-ring clearance, and crankshaft runout checks accompany the repair procedures.

Special-tool references include the crankcase separating tool YU-1135-A / 90890-01135 and flywheel puller YM-1189 / 90890-01189.

Carburetor Service and Cooling-System Tests

Carburetor instructions cover jets, the needle valve, float height, and reassembly; the venturi block remains assembled. Tuning charts relate jet and needle selection to throttle opening, weather, and running symptoms. Pilot-air-screw figures include examples rather than one universal factory setting.

Cooling coverage includes radiator inspection and water-pump impeller, bearing, and seal work. Pump reassembly notes flag the risk of damaging an oil-seal lip or dislodging its spring during shaft installation.

Brakes, Suspension, and Race Setup

Brake sections show piston and seal inspection, master-cylinder rebuilding, and leak checks after assembly. Cable-routing diagrams and fastening specifications help avoid trapped leads and fastener damage during reassembly.

Fork coverage includes damper-rod and base-valve inspection and oil-level setting. A specific caution addresses internal valve damage if the damper rod drops into the fork tube.

Rear-shock service: The section covers spring replacement, inspection, and external adjustments, without an internal damper rebuild procedure. Yamaha warns against opening the pressurized nitrogen cylinder or reservoir. Consult a qualified technician before major brake or suspension work.

Setup tables distinguish standard and LW suspension settings and regional rear-spring options. Transmission ratios, optional sprockets, and front- and rear-suspension symptom charts support track setup.

Ignition Fault Tracing

The no-spark chart works through the stop switch, ignition coil, spark-plug cap, pickup coil, and charging coils before the CDI unit. Wiring color codes and connector illustrations connect the resistance tests to the correct leads.

Examples of Cylinder Specifications and Wheelbase Differences

These figures are a small selection of the engine inspection data and model-specific dimensions in the manual.

For both models, cylinder-head combustion chamber capacity is listed as 7.14 cm³. Standard piston-to-cylinder clearance is 0.040–0.045 mm, with a 0.1 mm service limit.

The YZ85 wheelbase is 1,258 mm for U.S. and South African models and 1,255 mm for European, Canadian, Australian, and New Zealand models. The YZ85LW wheelbase is 1,286 mm.

PDF Navigation, Languages, and Page Count

Text search and diagram detail: Body text is searchable. Chapter bookmarks open the language-specific contents pages, whose linked entries lead to the relevant sections. Small wiring and connector labels are readable when enlarged; labels embedded in illustration images are not searchable.

The download contains one printable, 508-page PDF with English, French, and German text. That total includes the original covers and front matter, three memo pages, and two blank end pages.