1985–1988 Yamaha Badger 80 / YFM80 (YFM80N) ATV Service Manual (P/N LIT-11616-04-84)

Yamaha service manual for the 1985–1988 Badger 80 / YFM80, with repair procedures and specification tables identifying the YFM80N, model code 55X.

• Maintenance and adjustment: Valve-clearance adjustment, compression testing, throttle and speed-limiter settings, oil-strainer cleaning, and periodic inspection and lubrication schedules.

• Engine overhaul: Engine removal, crankcase separation, cylinder-head repair, valve-guide and seat work, piston inspection, camshaft checks, and timing-system assembly.

• Clutch and transmission: Centrifugal-clutch disassembly, one-way boss inspection, clutch-height adjustment, shift-cam and shift-fork checks, and transmission reassembly.

• Carburetor service: Mikuni VM16SH removal, disassembly, component inspection, fuel-level measurement, float-height adjustment, and a labeled sectional view.

• Chassis and shaft drive: Wheel-bearing replacement, rear drum-brake service, steering-knuckle and tie-rod inspection, toe-in adjustment, and final-drive disassembly.

• Electrical diagnosis: Starting, charging, and ignition troubleshooting charts, starter-motor inspection, relay tests, coil-resistance checks, and system-specific wiring diagrams.

This manual suits mechanics familiar with engine repair and electrical testing who have access to the specified measuring equipment and special tools.

Engine Overhaul and Timing Coverage

The engine chapter follows removal and disassembly through inspection, repair, assembly, and final adjustment. Internal checks cover cylinder wear, piston clearance, ring gaps, crankshaft runout, valve-seat contact, and camshaft condition, with component-specific limits and torque tables.

Coverage limits: Printed page 2-2 is missing, leaving the beginning of the cam-chain tension adjustment incomplete. Printed page 3-40 is also missing, interrupting engine reassembly around the oil-pump, oil-strainer, and drive-gear/starter installation sections.

The manual distinguishes work that requires engine removal from cylinder and flywheel-magneto work that can be performed with the engine installed. Its special-tool references connect the required equipment with the corresponding measurements, helping a shop prepare for the planned repair.

Clutch, Middle Gear, and Shaft Drive

Clutch assembly drawings distinguish the black and silver friction plates, bent clutch plate, thrust weight plate, and pressure plate. Adjustment charts address clutch boss height and friction-plate height rather than treating the clutch as a simple replacement assembly.

Middle-gear service includes U-joint bearing work and driven-gear shim selection. Shaft-drive coverage extends to the coupling gear, drive pinion, spring-loaded shaft assembly, and bearings; a dimensioned homemade-tool drawing accompanies the crankcase-separator application.

The bearing-care notes explain that spinning dry bearings with compressed air damages their running surfaces.

Carburetor Inspection and Adjustment

The carburetor chapter separates needle-valve, throttle-valve, jet-needle, and float inspection from reassembly and adjustment. The sectional view identifies the fuel, air, and mixture passages.

Step-by-step procedures cover fuel-level and float-height checks. The fuel-level procedure references Yamaha gauge YM-01312, while the float-height instructions explain the needle-valve contact condition required for the measurement.

Wheels, Brakes, and Steering

Chassis procedures cover wheel and hub removal, bearing replacement, rear-axle inspection, brake-shoe measurement, and brake-drum inspection. Steering coverage includes shaft bushings, knuckle spacers, tie-rod ends, and alignment checks.

The assembly illustrations show lubrication points and component orientation. Follow the factory procedures and use qualified technical expertise for brake work, fuel handling, battery service, and supporting the ATV during wheel removal.

Starting, Charging, and Ignition Tests

Separate troubleshooting charts address a starter that will not operate, charging faults, and missing or intermittent ignition spark. Tests cover the starter relay, starting circuit cut-off relay, starter motor, ignition coil, and magneto coils.

The YFM80N Wiring Diagram and Electrical Starting System diagram connect component numbers with wire-color codes. The Lubrication Diagram and Cable Routing drawings provide additional assembly references.

Battery-breather routing receives a specific caution: misplaced discharge can expose the frame to electrolyte and cause structural or cosmetic damage.

A Preview of Clutch and Carburetor Adjustment Data

Clutch assembly data specify a clutch boss height of 0.2–0.4 mm and a friction-plate height of 1.30–1.65 mm. These are separate measurements, supported by different washer- and plate-selection charts.

The carburetor section specifies a float height of 21.0 ± 0.5 mm, measured from the float-chamber mating surface with the gasket removed. The float arm rests against the needle valve without compressing it.

Bookmarked Chapters and Wiring Detail

Text search and diagram viewing: PDF text search is unavailable. Embedded bookmarks provide access to the seven chapters and selected subsections. Small wire-color codes and connector labels in the wiring diagrams require zooming for comfortable reading.

One printable English PDF contains 173 pages: 172 manual pages, including the symbol guide, index, and three divider/blank pages, plus one additional unnumbered wiring-diagram sheet.