2004–2009 Honda TRX450R / TRX450ER ATV Service Manual (P/N 61HP105)

This Honda service manual covers the 2004–2009 TRX450R and TRX450ER ATVs, including the kickstart and electric-start variants. It covers maintenance and repairs, separating the original models from the revised engine and electrical systems introduced after '05.

• Engine & Valvetrain: Unicam valve inspection and shimming, compression testing, camshaft and decompressor service, cylinder head overhaul, and piston inspection.
• Clutch & Transmission: Wet clutch, gearshift linkage, kickstarter, and TRX450ER starter clutch service, plus crankcase separation, transmission rebuilding, crankshaft inspection, and balancer timing.
• Fuel System: Carburetor removal, disassembly, cleaning, inspection, and assembly, with float level checks, pilot screw adjustment, and high-altitude settings.
• Lubrication & Cooling: Separate engine and transmission oil servicing, oil pump inspection, cooling system pressure testing, thermostat checks, and water pump overhaul.
• Hydraulic Brakes: Front and rear caliper and master cylinder disassembly, component inspection and assembly, brake bleeding, and parking brake adjustment.
• Chassis & Body: Seat, fender, and exhaust removal, steering and wheel bearing service, rear axle work, and suspension linkage and swingarm inspection.
• Electrical Systems: Variant-specific ignition and alternator tests, TRX450ER charging and starter diagnosis, lighting and switch checks, and cooling fan circuit testing.

Written for qualified professional technicians, this manual assumes workshop knowledge and access to the specified tools, particularly for engine, electrical, and brake work.

Unicam, Crankcase and Transmission Repair

Cylinder head procedures include valve guide replacement, seat refacing, cam timing, and shim selection. Inspection data cover cam lobe heights, valve spring free lengths, piston clearances, and transmission gear, bushing, shift fork, and drum wear.

The manual separates in-frame top-end work from crankcase service requiring engine removal. Exploded component views accompany clutch and gearbox disassembly, while assembly instructions address balancer alignment and the applicable fastener torque specifications.

For the After '05 titanium intake valves, lapping damages the thin oxide coating; the manual distinguishes this restriction from the earlier intake valve procedures.

Carburetor, Oil Circuit and Cooling Service

Carburetor identification distinguishes QA16A on the original models from FCR10A on later TRX450ER models and FCR11A on later TRX450R models. The fuel chapters include accelerator pump service, with special tool references for float level and pilot screw work.

Lubrication diagrams show the separate engine and transmission oil arrangements. Pump rotor inspection, sealing points, and oil cooler service are covered where applicable; the maintenance instructions warn that a reversed oil filter can cause severe engine damage.

Cooling coverage includes radiator cap and system pressure tests, coolant replacement and air bleeding, thermostat inspection, and water pump mechanical seal and bearing replacement. A coolant gravity chart supports coolant condition checks.

Ignition and Starting Fault Diagnosis

Electrical procedures distinguish the kickstart ignition system from TRX450ER battery, charging, starter motor, relay, and interlock testing. Circuit diagrams, cable and harness routing drawings, and model-specific wiring diagrams support component and connector identification.

The later models' closed-throttle position detection tests help distinguish an ignition cutoff caused by throttle switch or circuit faults from other ignition problems. Coil, exciter, and pulse generator peak voltage tests are assigned to the applicable systems, with peak voltage adapter and meter requirements stated alongside the checks.

Suspension, Steering and Brake Work

Suspension procedures cover shock removal, inspection and replacement, mounting bearings, linkage, and swingarm service. Internal shock absorber overhaul is not included; damaged shock assemblies are replaced.

Steering procedures include tie-rod inspection and toe adjustment. Rear axle locknut instructions distinguish actual torque from torque wrench readings when using the specified tool, while brake sections cover hydraulic component overhaul and parking brake service.

Always adhere to standard workshop safety protocols and consult a certified technician before undertaking major engine or chassis work on this equipment.

Valve Clearance and Transmission Oil Examples

The valve inspection specifications list intake clearance at 0.16 ± 0.03 mm and exhaust clearance at 0.28 ± 0.03 mm, with the engine cold, below 35°C (95°F). These figures accompany the Unicam inspection and shim adjustment procedures.

For the '04–'05 models, the transmission oil capacity after draining is 0.55 liter. The manual distinguishes this service refill quantity from capacities following disassembly and from the separate engine oil supply.

PDF Search, Bookmarks and Page Contents

Search and navigation: The PDF has a searchable OCR layer across most service pages and bookmarks for the contents and all chapters. The cover and main contents page lack searchable text; small wiring diagram labels are image-based and require enlargement for reading. Printed pages 16-19 and 16-20 appear in reverse order.

File contents: One printable English-language PDF with 523 pages total, including the cover and three introductory pages.