2004 Yamaha YXR660FAS UTV Service Manual (P/N LIT-11616-17-23)

The 2004 Yamaha YXR660FAS service manual covers maintenance, diagnosis, and repair for model code 5UG1, including selectable 2WD/4WD and differential lock. Yamaha publication P/N LIT-11616-17-23 is the first edition, dated July 2003.

Text Search, Wiring Detail, and PDF Contents

Search and diagram navigation: Text search is available across the service chapters, but there are no embedded PDF bookmarks. Small connector labels and wire-color codes in the checked wiring diagrams are readable when enlarged.

This printable, English-language 421-page PDF includes 17 pages of front matter, 400 pages of service chapters, two blank end pages, the back cover, and the final vehicle wiring diagram.

Engine Overhaul, Shaft Drive, and Electrical Diagnosis

The selected topics below show the main repair areas. The manual also includes spark-arrester cleaning and headlight-beam adjustment procedures.

• Engine repair: Engine removal, cylinder-head and valve service, cylinder and piston inspection, crankshaft work, and oil-pump checks.

• Clutch and transmission: Primary and secondary sheave disassembly, centrifugal-clutch inspection, internal transmission checks, and reassembly procedures.

• Shaft drive: Constant velocity joint service, differential inspection, middle-gear shim selection, final-drive setup, and gear-lash adjustment.

• Cooling system: Radiator inspection, coolant replacement and bleeding, water-pump disassembly, seal installation, and oil-cooler checks.

• Fuel system: Fuel-pump operation testing, carburetor disassembly and inspection, float-height measurement, and fuel-level adjustment.

• Brakes and chassis: Hydraulic brake bleeding, master-cylinder and caliper service, steering-knuckle inspection, and suspension-arm checks.

• Electrical diagnosis: Circuit diagrams and troubleshooting charts for ignition, starting, charging, lighting, drive selection, and carburetor heating.

Yamaha wrote this manual primarily for its dealers and qualified mechanics, assuming an existing understanding of mechanical principles and vehicle repair procedures.

Engine Inspection and Internal Repair

Step-by-step repair instructions extend from engine removal and crankcase separation to camshaft and decompression-system checks. The transmission section examines the shift forks, shift drum, drive axle, secondary shaft, and driven sprocket.

Factory tolerances, clearance specifications, tightening-torque tables, and wear limits let mechanics compare inspected components with Yamaha’s standards during maintenance and overhaul. Exploded diagrams and accompanying job instruction charts identify parts and clarify the work described.

Carburetor and Fuel Supply

The MIKUNI BSR42 section documents component inspection, assembly, float measurement, and fuel-level adjustment. Fuel-pump operation checks complement the carburetor procedures, while the electrical chapter separately addresses carburetor-heater faults.

Water Pump and Cooling Circuits

Water-pump service includes impeller inspection and seal installation. Coolant flow diagrams and oil flow diagrams show the related pipes, hoses, and component connections; cable-routing illustrations document hose and harness placement.

Shaft-Drive Setup and Service Limits

Middle-gear shim selection and final-drive pinion and ring-gear positioning receive separate procedures. The gear-lash measurement tool is identified as YM-01467 / 90890-01467.

The factory-assembled differential gear unit must remain intact during the surrounding housing service. Its inspection, lash adjustment, and operation checks are covered; the gear motor is tested as an assembly and must not be disassembled.

The middle driven shaft section flags the bearing retainer’s left-hand threads. It also warns that direct hydraulic-press loading on the pinion end damages its threads.

Brakes, Steering, and Suspension

Master-cylinder and caliper sections cover inspection, assembly, and installation. Steering-knuckle bearing work, tie-rod checks, steering-assembly service, and suspension-arm inspections extend the chassis coverage beyond routine adjustments.

Brake and steering work requires proper vehicle support and the manual’s specified checks before the vehicle returns to service.

Electrical Fault Finding

System-specific circuit diagrams, connector layouts, wire-color codes, and electrical test values support fault tracing between switches, relays, wiring, and components. The electric starting system also has a starting-circuit operation diagram.

Troubleshooting addresses hard starting, poor idle performance, gear shifting, clutch operation, overheating, and unstable handling.

Examples of Engine, Carburetor, and Final-Drive Specifications

Standard engine compression pressure is listed at 1,324 kPa (188.31 psi) at sea level and 850 r/min. Cold intake-valve clearance is specified at 0.10–0.15 mm.

The fluid tables distinguish a 2.20 L engine-oil refill with filter replacement from the 0.25 L periodic final-gear oil change quantity.

Carburetor float height is specified at 13 mm, with measurement notes covering gasket and needle-valve position. Final gear backlash is 0.1–0.3 mm in both the specification table and the adjustment section.