Onan Gasoline Engine Service Manual (16, 18, 20 & 24HP) John Deere (P/N CTM2)

The official John Deere publication CTM2 (P/N 130495) provides a comprehensive 223-page PDF of 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, engine application charts, metric torque specification tables, dimensional wear tolerance charts, diagnostic testing views, valve clearance charts, and component cutaway drawings 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.
• Covers extensive maintenance and rebuild procedures for essential engine systems including carburetors, stators, rectifier-regulators, ignition coils, breaker points, condensers, and solenoid drive starters.
• Outlines precise teardown and measurement sequences for bottom-end and lubrication hardware, covering crankshafts, main bearings, connecting rods, oil pumps, oil filter adapters, governor assemblies, and Bendix drive starters.

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, troubleshooting, and testing. Specific topics include air cleaner and breather maintenance, intake manifold service, cylinder head removal, valve train work, flywheel assembly, camshaft repair, as well as servicing oil bases, oil pressure regulating valves, and overrunning clutches.

To help shops keep complex work in-house instead of outsourcing to expensive specialized facilities, this guide outlines advanced step-by-step procedures. These include deglazing cylinder bores with a flex-hone, measuring connecting rod bearing clearance using the PLASTIGAGE method, testing starter armature windings for short circuits with a growler, and cutting valve seats to a precise 45-degree angle. By providing exact factory wear tolerances and clearance specifications directly from the manufacturer, this manual allows technicians to immediately determine if a component requires simple replacement or specialized machining, effectively eliminating costly trial-and-error at the workbench. 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.