Onan P218G

Onan P218GThe Onan P218G (Performer 18) is a 782 cc (47.7 cu-in) two-cylinder air-cooled four-stroke internal combustion small gasoline engine with a horizontal shaft manufactured by Onan for general-purpose applications.

The P218G engine has an L-head design with two flat cylinders, an aluminum cylinder block, a carburetor fuel system, an electronic battery ignition system, and an electric starter.

The cylinder bore is 82.55 mm (3.25 in) and the piston stroke is 73.01 mm (2.87 in), the compression ratio rating is 7.0:1. The Onan P218G engine produced 18.2 PS (13.4 kW; 18.0 HP) at 3,600 rpm of horsepower.

The breakdown of the engine code is as follows:

  • P – Engine Family
  • 2 – Two cylinder
  • 18 – 18.0 BHP power
  • G – Gasoline

General information

Engine Specifications
ModelOnan P218G (Performer 18)
Type4-stroke, L-head, flat
Displacement782 cm3 (47.7 cu-in)
Max. horsepower18.2 PS (13.4 kW; 18.0 HP) at 3,600 rpm
Max. torque
Fuel systemCarburetor with fixed main jet
Cooling systemForced-air
Ignition systemElectronic battery ignition system ignition system
Lubricating systemForced lubrication
Starting systemElectric starter
PTO shaft rotationClockwise (viewed from flywheel)

Cylinder Block and Head

Cylinder block
Compression ratio:7.0:1
Bore x Stroke82.55 X 73.00 mm (3.25 x 2.87 in)
Sleeve internal diameter82.530-82.550 mm (3.2492-3.25 in)
Piston skirt outer diameter82.420-82.440 mm (3.2449-3.2457 in)
Ring end gapTop/Second0.076-0.203 mm (0.003-0.008 in)
Connecting rod small end ID17.470-17.480 mm (0.6878-0.6882 in)
Piston pin outer diameter17.463-17.468 mm (0.6875-0.6877 in)
Crankpin diameter41.280-41.300 mm (1.6252-1.626 in)
Crankshaft main journal diameter50.780-50.800 mm (1.9992-2 in)
Cylinder Head
Valve Arrangement:L-haed, gear driven
Valves:4 (2 per cylinder)
Stem outer diameter (standard):INTAKE7.099-7.112 mm (0.2795-0.2800 in)
EXHAUST7.061-7.074 mm (0.2780-0.2785 in)
Valve spring free length:40.640 mm (1.6 in)
Lobe height:INTAKE28.880 mm (1.1370 in)
EXHAUST29.390 mm (1.1571 in)

Service Information

Maximum speed3,600
Cylinder compression517-793 kPa (75 to 115 psi)
Valve clearance
Intake valve clearance0.130 mm (0.0051 in)
Exhaust valve clearance0.330 mm (0.0130 in)
Oil system
Oil type:API SF, SF/CC, or SF/CD
Recommended oil:SAE 5W-30, 10W-30, 30W, 40W
Oil capacity Without oil filter:
Standard base: 1.4 L (1.5 US. qt, 1.2 Imp. qt.)
High capacity base: 2.6 L (2.75 US. qt, 2.3 Imp. qt.)
Oil filter: 0.3 L (0.32 US. qt, 0.26 Imp. qt.)
Ignition system
Ignition timing20° B.T.D.C.
Spark plugNGK BPR5EFS, Champion RS14YC
Spark plug gap0.640 mm (0.0252 in)
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We try to use verified sources and official documentation, however, differences between sources or errors in entering information may occur. We do not provide advice on technical issues related to the engines operation or repair. We do not recommend using provided information for engines repairing engines or spare parts ordering, use only official service manuals and spare-parts catalogs.

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