Onan Gasoline Engine Service Manual (16, 18, 20 & 24HP) - John Deere

The official John Deere publication CTM2 provides comprehensive maintenance and data for the 16–24HP Onan engine series, covering everything from cylinder block internals to fuel system components and valve timing specifications.

• Built for technicians servicing 16, 18, 20, and 24 HP Onan Engines (models B43E, B43G, B48G, P218G, P220G, and T260).
• Contains 56 individual diagrams, including component exploded views, torque-sequence illustrations, and engine application charts to speed up shop workflow.
• Details factory-recommended procedures for engine components such as air cleaner assemblies, cylinder heads, intake manifolds, valves, and pistons.
• The only edition explicitly distinguishing T260 engine service procedures from the standard B43/P218 variant assembly instructions.

Engine Service and Component Walkthrough

This documentation covers the technical procedures necessary for the overhaul and maintenance of two-cylinder, four-cycle power units. It gives clear direction on removing and installing engine components, with a heavy emphasis on diagnostic analysis and testing. Specific topics include air cleaner and breather maintenance, intake manifold service, cylinder head removal, valve train work, flywheel assembly, and camshaft repair. The layout mirrors the original factory workshop structure to seamlessly guide experienced service technicians through complex teardown and reassembly routines. Working on internal combustion engines involves high pressures and flammable liquids. Always verify your setup and consult a certified professional before performing service on this equipment to avoid personal injury or mechanical damage.

Specification and Torque Data Preview

Engine specifications are meticulously documented across the supported models. You will find detailed displacement alongside bore and stroke charts to aid in diagnostics. Crucial torque values for fasteners—like cylinder head nuts and flywheel cap screws—are provided so you can ensure accurate assembly on the bench. The manual lists intake valve clearance at 0.13 mm and exhaust valve clearance at 0.33 mm. Camshaft gear backlash for the B43E/G and B48G models is strictly specified at 0.03 to 0.15 mm. Most connecting rod cap nut torques are listed at 18 ± 1 N·m. However, the T260 cap screws require a specific 20 ± 1 N·m.