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
Model Onan P218G (Performer 18)
Type 4-stroke, L-head, flat
Displacement 782 cm3 (47.7 cu-in)
Max. horsepower 18.2 PS (13.4 kW; 18.0 HP) at 3,600 rpm
Max. torque
Fuel system Carburetor with fixed main jet
Cooling system Forced-air
Ignition system Electronic battery ignition system ignition system
Lubricating system Forced lubrication
Starting system Electric starter
PTO shaft rotation Clockwise (viewed from flywheel)

Cylinder Block and Head

Cylinder block
Compression ratio: 7.0:1
Bore x Stroke 82.55 X 73.00 mm (3.25 x 2.87 in)
Sleeve internal diameter 82.530-82.550 mm (3.2492-3.25 in)
Piston skirt outer diameter 82.420-82.440 mm (3.2449-3.2457 in)
Ring end gap Top/Second 0.076-0.203 mm (0.003-0.008 in)
Connecting rod small end ID 17.470-17.480 mm (0.6878-0.6882 in)
Piston pin outer diameter 17.463-17.468 mm (0.6875-0.6877 in)
Crankpin diameter 41.280-41.300 mm (1.6252-1.626 in)
Crankshaft main journal diameter 50.780-50.800 mm (1.9992-2 in)
Cylinder Head
Valve Arrangement: L-haed, gear driven
Valves: 4 (2 per cylinder)
Stem outer diameter (standard): INTAKE 7.099-7.112 mm (0.2795-0.2800 in)
EXHAUST 7.061-7.074 mm (0.2780-0.2785 in)
Valve spring free length: 40.640 mm (1.6 in)
Lobe height: INTAKE 28.880 mm (1.1370 in)
EXHAUST 29.390 mm (1.1571 in)

Service Information

Maximum speed 3,600
Cylinder compression 517-793 kPa (75 to 115 psi)
Valve clearance
Intake valve clearance 0.130 mm (0.0051 in)
Exhaust valve clearance 0.330 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 timing 20° B.T.D.C.
Spark plug NGK BPR5EFS, Champion RS14YC
Spark plug gap 0.640 mm (0.0252 in)
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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