1985–1987 Honda TRX250 Fourtrax ATV Factory Service & Repair Manual (P/N 61HA800)

This 233-page PDF covers the 1985–1987 Honda TRX250 FourTrax and its 246 cc air-cooled, chain-driven OHC single, dual-valve carburetor, semi-automatic wet clutch, five-speed constant-mesh transmission with reverse, and shaft final drive. Identification pages show where the frame, engine, and carburetor numbers are located, while repair differences are organized as ’85 and After ’85 rather than by published serial-number ranges. It is suited to experienced mechanics and mechanically proficient owners who already understand standard shop practice; the manual expressly omits detailed explanations of standard workshop procedures and general safety principles.

• Year-specific changes: Distinguishes ’85 and After ’85 cable and harness routing, crankcase-breather routing, tire data, steering-lock and front-wheel service, rear-brake hardware, and handlebar-switch checks.
• Engine repair: Covers engine removal and installation, cylinder-head disassembly, camshaft and cam-chain timing, valve-guide replacement and seat refacing, cylinder and piston inspection, and compression checks.
• Clutch and drivetrain repair: Follows both clutch systems through removal, inspection, and installation, then continues through oil-pump and kick-starter service, starter-clutch and shift-linkage work, crankcase separation, transmission inspection, output-gear setup, and shaft final-drive repair.
• Chassis and brake work: Includes steering-stem and front-arm service, kingpin and wheel-bearing replacement, shock disassembly, front hydraulic drum-brake bleeding and repair, rear cable-operated drum-brake service, rear axle work, and swingarm inspection.
• Fuel and electrical diagnosis: Provides carburetor overhaul and synchronization, pilot-screw and high-altitude adjustment, CDI and ignition-coil tests, charging-system checks, starter-motor inspection, switch testing, and oil-temperature warning diagnosis.
• Workshop reference: Supplies assembly views, troubleshooting charts, a full wiring diagram, special-tool references, component torque data, fluid specifications, wear limits, clearances, and electrical test values.

Engine and Drivetrain Service Depth

The top-end chapters go well beyond routine valve adjustment. They document rocker-arm and camshaft measurement, cam-chain tensioner service, valve-guide removal and reaming, valve-seat contact inspection and refacing, piston-ring checks, cylinder measurement, and final cam-timing verification. The manual also identifies the assemblies that can be serviced with the engine still in the frame, including the cylinder head, cylinder and piston, clutch, oil pump, alternator, starter motor, kick starter, carburetor, and gearshift linkage.

For internal drivetrain work, the crankcase section covers case separation, crankshaft and balancer timing, transmission gear and shift-fork inspection, bearing replacement, and reassembly. Output-drive repair includes matched gear replacement, adjustment-shim selection, backlash measurement, and tooth-contact pattern checks. The rear final-drive chapter adds pinion and ring-gear disassembly, spacer selection, contact-pattern correction, backlash verification, and assembly-preload checks.

Chassis, Brake, and Electrical Coverage

The chassis chapters address toe-in, camber and caster inspection, tie rods, kingpins, steering bearings, front arms, shocks, rear axle bearings, swingarm pivots, wheels, and tire repair. Brake coverage matches the actual TRX250 configuration: hydraulic leading-trailing front drums and a cable-operated leading-trailing rear drum. Procedures include master-cylinder and wheel-cylinder inspection, shoe and drum service, brake adjustment, hose and pipe checks, and hydraulic-system bleeding.

Electrical diagnosis is organized around measured tests rather than parts swapping. The ignition section covers the coil, exciter coil, CDI unit, pulse generator, and timing; charging coverage includes battery condition, leakage, charging output, regulator/rectifier, and alternator-coil checks. The starter chapter includes brush, commutator, field-coil, and relay inspection. Lighting and switch sections provide continuity charts plus a dedicated fault-isolation chart for the oil-temperature warning circuit.

Diagrams, Tools, and Repair Cautions

Useful visual references include the full wiring diagram with wire-color codes and switch-continuity matrices, ’85/After ’85 cable-routing views, the engine lubrication diagram, camshaft timing-mark views, output-gear and final-drive tooth-contact diagrams, and symptom-based engine and handling troubleshooting charts.

The tool index identifies Honda equipment by number and notes U.S. substitutes or availability. Examples include crank assembly tool set 07931-KF00000, clutch holder 07923-HA80000, pinion holder 07924-HA00000, and CDI inspection adapter 07508-0012500.

The carburetor section warns that forcing the pilot screw against its seat will damage the seat. During engine installation, poor alignment can damage mounting threads, wiring, cables, or the oil-temperature sensor; interchanging the neutral and reverse switch leads can also create a false neutral indication and unexpected reverse movement. Separate cautions address fuel vapors, battery gas and electrolyte, brake-fluid damage, safe vehicle support, and brake dust that may contain asbestos.