Honda ATC 90 & 110 Three-Wheeler 1973–1981 Shop Manual (P/N 6291806)

• Spans the 1973–1981 Honda ATC 90 and ATC 110 three-wheelers, detailing engine, chassis, and electrical system service for the US90 and ATC90K variants
• Official Honda factory publication P/N 6291806, originally released in 1980
• Features 116 pages of exploded-view diagrams, electrical schematics, and mechanical assembly illustrations
• Indexed layout guarantees fast navigation through the engine, steering, transmission, and braking sections
• Serves as the definitive reference for the transition from the early US90 to the ATC90K3, specifically documenting updates to the drive mechanism and steering assembly

Component and System Documentation

This Honda ATC 90 & 110 service manual delivers structured technical data for maintaining these classic air-cooled three-wheelers. The document outlines disassembly and reassembly sequences for the engine, drivetrain, front fork, and steering head components, alongside specific data on the clutch assembly and internal transmission gear sets.

Technical sections dive into the recoil starter, carburetion tuning, and cylinder head servicing. It provides clear, exploded-view diagrams that map out the exact sequence of snap rings, oil seals, and bearings required for engine housing and hub maintenance. Note that working on vintage ATVs involves inherent risks; always adhere to the provided factory specifications and proper shop safety practices to ensure safe operation and prevent injury.

Specifications and Reference Values

The manual highlights factory-defined tolerance charts for piston rings, valve guides, and clutch plates, giving you the standard measurements and wear limits needed to evaluate parts. Fluid capacities are clearly documented at 1.0 liters for engine oil (SAE 10W-40 recommended) and 6.5 liters for fuel.

Critical torque values for major assemblies are also laid out, including cylinder head nuts at 14.5–18.1 lbs-ft (1.5–2.0 kg-m) and rear driven sprocket bolts at 29–34.7 lbs-ft (4–4.8 kg-m). Understanding what an OEM service publication contains is essential for planning a thorough restoration or routine maintenance on these classic three-wheelers.

This page provides a contents overview of the manual and does not contain step-by-step diagnostic instructions. The official 116-page Honda factory publication equips technicians with the necessary tolerances, assembly diagrams, and technical specifications for complete engine and chassis service.