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General| Engine Model | NH |
|---|---|
| Cylinders | 2 |
| Fuel Type | Gasoline |
| Governor Type | Mechanical |
| Ignition System | Battery |
| Starter | Electric |
| Engine Type | 4-cycle, air-cooled |
Fire safety, securing parts, caution with moving machinery and hot surfaces.
Flammability of fuel, toxicity of exhaust, carbon monoxide risks.
Precautions for battery operation and cooling system pressure.
Manual covers mechanical/electrical info for troubleshooting and servicing.
How to identify model and spec number from the unit nameplate.
Lists key engine parameters like bore, stroke, displacement, power.
Details valve clearances, ignition timing, and compression specs.
Specifications for cylinder bore, main bearings, and crankshaft.
Specifications for connecting rods, camshaft, and pistons.
Clearances for pistons, rings, valve stems, and guides.
Specifications for piston pin, intake/exhaust valves, and tappets.
Specifications for valve springs and gear backlash.
Table listing torque values for various engine components.
Lists special tools available from Onan for engine service.
Guide to identify causes of engine troubles across various systems.
Guidelines for engine air intake and exhaust for optimal cooling.
Installation advice for open air and Vacu-Flo cooling systems.
Guidelines for exhaust system setup and carburetor air intake.
Advice on engine mounting methods and angles.
Importance of regular inspection and maintenance of the exhaust system.
Dimensions for standard, Rockford Clutch, and Gear Reduction PTO shafts.
Guide for setting up and installing belt drives.
Installation of flexible couplings and reduction gear drives.
Procedures for clutch installation and gearbox oil changes.
How to connect automotive type separate starter batteries.
Steps to protect the engine for storage over 30 days.
Procedures for taking the engine out of storage and preparing it.
Information on oil changes, viscosity, and checking oil level.
Procedure for changing the oil filter element.
How to service the crankcase breather valve for optimal performance.
Explanation of the engine's pressure lubrication system and oil pump.
Description and inspection of the oil by-pass valve.
Instructions for adjusting idle and main mixture screws.
Procedures for measuring and adjusting carburetor float levels.
General instructions for carburetor disassembly, cleaning, and repair.
Steps for reassembling and installing Nikki carburetors.
Steps for reassembling and installing other carburetor types.
Steps to test the pulse fuel pump's vacuum and pressure.
Procedure for testing mechanical fuel pump fuel flow.
Test values for pulse pumps and repair instructions.
Steps for removing and repairing mechanical fuel pumps.
Detailed steps for repairing mechanical fuel pumps.
Information on electric fuel pumps and their service.
Procedures for testing and servicing electric fuel pumps.
Function and testing of the external fuel shutoff valve.
How to access and replace fuel filters within pumps.
How the electric choke works and how to adjust it.
Troubleshooting and repair for the electric choke system.
Instructions for cleaning and oiling the air cleaner pre-cleaner.
Steps for adjusting carburetor, linkage, and spring tension.
How to adjust governor linkage for proper throttle control.
How spring tension affects engine speed.
Adjusting governor sensitivity for stable speed regulation.
Adjusting speed and sensitivity for variable speed governors.
How to replace and adjust breaker points for timing.
Testing ignition timing using continuity tests.
Procedures for testing ignition coil primary and secondary resistance.
Spark plug maintenance and replacement advice.
How to check battery cells with a hydrometer and clean terminals.
Safe procedures for jump starting a weak battery.
Overview of different flywheel alternator systems used.
Key points to remember when testing or servicing the flywheel alternator.
Specific tests for the 20 Amp Synchro alternator system.
Troubleshooting steps for no output or regulation issues.
Procedure to test the alternator's output voltage.
Table of tests and values for Phelon alternator systems.
Components and basic function of the electric starter system.
Procedures for removing and disassembling the starter motor.
Inspecting pinion gear, clutch, brushes, and armature.
Tests for armature grounds, shorts, and field coil integrity.
How to check and correct commutator runout.
Checking armature shaft runout and cleaning parts.
Steps for assembling the starter motor.
Post-overhaul tests for the starting motor.
Procedure for checking starter-to-flywheel gear lash.
Step-by-step guide for taking the engine apart.
Guidelines for reassembling the engine correctly.
How to perform a compression test on the engine.
Procedure for checking and adjusting valve tappet clearance.
Inspecting valves, seats, guides, and cylinder block for wear.
Inspecting valve stems and guides for wear.
Steps for installing new valve guides.
Checking valve springs and rotators for condition.
Procedures for removing and installing valve seat inserts.
Tappet inspection and valve face/seat grinding procedures.
Checking valve head margin and understanding interference angles.
Procedures for safely removing the engine flywheel.
Steps for removing and installing the gear cover.
Information on governor cup, flyballs, and installation.
Procedures for replacing crankshaft and camshaft gears.
Steps for removing pistons and connecting rods from cylinders.
How to remove piston rings using a spreader.
Cleaning piston surfaces and ring grooves.
Procedures for inspecting pistons and connecting rods for wear.
Steps for cleaning the cylinder block after disassembly.
Inspecting the cylinder block for cracks, wear, and flatness.
Checking cylinder bores for wear, taper, and out-of-roundness.
Methods for measuring cylinder bore dimensions for wear.
Procedures and precautions for reboring cylinder bores.
Using precision hones to achieve desired cylinder finish.
Process of deglazing bores for piston ring break-in.
Inspecting crankshaft journals and drilled passages.
Procedure for shot peening crankshaft fillets.
Inspecting and replacing crankshaft and camshaft bearings.
Procedures for installing front and rear main bearings.
How to check and adjust crankshaft endplay.
Procedures for replacing oil seals in bearing plates and gear covers.
Installing piston rings onto pistons.
Steps for installing pistons and connecting rods into the cylinder.
Steps for removing cylinder heads and cleaning carbon deposits.
Procedures for installing new cylinder head gaskets and heads.
Steps to test cylinder head studs for integrity.
Procedures for replacing cylinder head studs.
Using a repair fixture and drilling for stud replacement.
Steps for removing and installing the intake manifold gasket.
Diagram showing engine control wiring with options.
Wiring diagram for the Phelon 15 Amp alternator system.
Wiring diagram for the Syncro 20 Amp alternator system.
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