1993–2005 Honda TRX90 ATV Service Manual

This Honda service manual covers the 1993–2005 TRX90 ATV, including its air-cooled engine, semi-automatic transmission, and recoil starter. It contains model-specific procedures and is designed to be used with Honda's separate Common Service Manual, which is not included in this PDF.

Text search, navigation, and wiring detail: Text search is not available. Embedded bookmarks link to the contents, all 15 sections, and the index. Small wiring labels are readable when enlarged.

• Engine repair: Cylinder head, cylinder, and piston removal; valve-train disassembly; cam sprocket timing, decompressor cam checks, and cam chain tensioner servicing.

• Clutch and transmission: Centrifugal and change clutch disassembly, gearshift linkage service, crankcase separation, and mainshaft, countershaft, and shift drum assembly.

• Fuel and lubrication: Carburetor and throttle valve disassembly, air screw and high-altitude adjustments, oil pump service, and strainer screen and centrifugal filter cleaning.

• Recoil starter: Fault diagnosis, ratchet and reel disassembly, starter rope installation, and recoil spring assembly.

• Chassis and brakes: Drum brake and equalizer service, steering shaft and tie-rod removal, swingarm repair, rear axle work, and shock absorber servicing.

• Ignition diagnosis: CDI circuit checks, ignition coil and alternator testing, wiring diagrams, switch continuity charts, and symptom-based troubleshooting flowcharts.

Honda wrote this manual for readers with basic maintenance knowledge of Honda motorcycles, motor scooters, or ATVs; standard workshop procedures are assumed.

Engine Repair and Transmission Service

The cylinder head, cylinder, and piston can be serviced with the engine in the frame. Crankshaft and transmission work requires engine removal and crankcase separation, a useful distinction when planning a repair.

Assembly illustrations distinguish the centrifugal clutch, one-way clutch, and change clutch. Mainshaft, countershaft, and shift drum layouts identify the gears, washers, circlips, and shift forks involved in internal transmission work.

The crankcase procedure warns that the countershaft's exposed sprocket end can damage the oil seal during transmission removal or installation.

Carburetor Settings and Lubrication

The PB1AA carburetor section distinguishes standard and high-altitude jetting and explains air screw adjustment after overhaul. It warns that using the high-altitude setup at lower elevations can overheat and damage the engine.

The Lubrication System Diagram traces oil delivery to engine and transmission components. Oil pump assembly instructions identify shaft alignment points, while the Service Access Guide shows which panels must be removed for individual maintenance jobs.

Frame, Brakes, and Suspension

Frame and body procedures cover fenders, the fuel tank, muffler, and exhaust pipe. Front-end illustrations detail the brake equalizer, kingpins, steering shaft, and tie-rods; rear-end coverage extends to swingarm bushings and the axle bearing holder.

Cable & Harness Routing drawings show the throttle and brake cable paths alongside ignition wiring.

Front shock absorbers are replaced as complete assemblies. The rear shock section illustrates spring and damper separation using a spring compressor, with general procedures referenced to the Common Service Manual.

Follow the manual's precautions for secure vehicle support, hazardous fluids, hot exhaust components, and brake dust during chassis maintenance.

CDI Ignition and Fault Tracing

The no-spark flowchart links connector checks with tests of the ignition coil, alternator exciter coil, pulse generator, and CDI circuits. This helps distinguish a component fault from a wiring or switch fault before replacement parts are selected.

The ignition System Location drawing and Wiring Diagram identify neutral and top gear switch circuits, wire-color codes, and ignition/engine-stop switch continuity. Ignition timing inspection is covered, but the CDI timing setting is not adjustable.

Separate troubleshooting charts address hard starting, loss of power, poor running at low and high speeds, and handling problems.

Technical Specifications and Service Tools

Factory tables provide engine and chassis torque values, wear limits, valve clearances, lubricant specifications, carburetor settings, and electrical test data. Tool references for repair work include clutch holder 07HMB-HB70100 and flywheel puller 07733-0010000.

TRX90 PDF Contents and Page Count

The manual comes as one printable English PDF. Its 125 pages include 110 pages across 15 technical sections, one cover page, four introductory pages, nine memo pages, and a one-page index.