Onan B48G

Onan B48GThe Onan B48G is a 0.8 L (782 cc, 47.7 cu·in) natural aspirated two-cylinders four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, for general-purpose applications.

Cylinder bore and piston stroke are 82.55 mm (3.25 in) and 73.00 mm (2.87 in), respectively. The compression ratio rating is 7.0:1.

This engine produced 20.3 PS (14.9 kW; 20.0 HP) at 3,600 rpm of horsepower and 43.0 N·m (4.4 kg·m, 31.7 ft·lb) of torque.

The Onan B48G features:

  • L-head design
  • Automotive type battery ignition system ignition system
  • Carburetor fuel system
  • Forced lubrication system
  • Air-cooling system
  • Electric starter

General information

Engine Specifications
Engine modelB48G
Engine type4-stroke, L-head, two-cylinders
Displacement782 cm3, (47.72 cu·in)
Max. horsepower20.3 PS (14.9 kW; 20 HP) at 3,600 rpm
Max. torque43.0 N·m (4.4 kg·m, 31.7 ft·lb)
Cooling systemForced air
Air cleaner
Lubricating systemForced lubrication
Ignition systemAutomotive type battery ignition system
Fuel systemCarburetor
Fuel usedUnleaded gasoline (octane number 86 or higher)
Starting systemElectric starter
Dimensions (L x W X H)
Dry weight

Cylinder Block and Head

Cylinder block
Compression ratio:7.0:1
Cylinder bore:82.55 mm (3.25 in)
Piston stroke:73.00 mm (2.87 in)
Cylinder internal diameter (standard):82.530-82.550 mm (3.2492-3.25 in)
Piston skirt outer diameter (standard):82.42-82.44 mm (3.2449-3.2457 in)
Number of piston rings (compression / oil):2/1
Connecting rod small end diameter (standard):17.470-17.480 mm (0.6878-0.6882 in)
Piston pin diameter:17.463-17.468 mm (0.6875-0.6877 in)
Ring end gap (Top):0.250-0.510 mm (0.0098-0.0201 in)
Ring end gap (Second):0.250-0.510 mm (0.0098-0.0201 in)
Number of main bearings:2
Crankshaft main journal diameter:50.780-50.800 mm (1.9992-2 in)
Crankpin journal diameter:41.280-41.300 mm (1.6252-1.626 in)
Crankshaft center distance:36.5 mm (1.435 in)
Cylinder head
Valve arrangement:L-head, gear driven
Valves:2 (4 valves in total)
Valve steam diameter (INTAKE):8.700-8.710 mm (0.3425-0.3429 in)
Valve steam diameter (EXHAUST):8.660-8.670 mm (0.3409-0.3413 in)
Valve spring free length (INTAKE):42.210 mm (1.6618 in)
Valve spring free length (EXHAUST):42.210 mm (1.6618 in)
Camshaft lobe height (INTAKE):29.570-29.720 mm (1.1642-1.1701 in)
Camshaft lobe height (EXHAUST):29.440-29.590 mm (1.1591-1.165 in)
Camshaft journal diameter :34.900-34.910 mm (1.374-1.3744 in)

Service Data

Cylinder compression:517-793 kPa (75 to 115 psi)
Valve clearance
Intake valve clearance (COLD):0.130 mm (0.0051 in)
Exhaust valve clearance (COLD):0.330 mm (0.013 in)
Oil system
Lubrication system:Forced lubrication
Oil type:SF, SF/CC, or SF/CD
Recommended oil:SAE 10W-30
Oil capacity: Without oil filter: 1.4 L (1.48 US. qt, 1.23 Imp. qt.)
With oil filter: 1.7 L (1.8 US. qt, 1.5 Imp. qt.)
Fuel system
Ignition system
Type:Automotive type battery ignition system
Ignition timing: Spec A&B: 20° B.T.D.C.
Spec C: 16° B.T.D.C.
Spark plug:NGK BPR5EF, Champion RS14YC
Spark plug gap:0.640 mm (0.0252 in)
Ignition coil air gap Spec A&B: 0.530 mm (0.020 in)
Spec C: 0.410 mm (0.016 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.

ATTENTION! Dear visitors, this is an informational database of technical specifications, we are not a parts supplier or a marketplace.

We try to use official documentation and verify the published data, but errors may occur. In addition, specifications of machinery and equipment may vary depending on markets and modifications. We do not recommend the use of this data for spare parts or repairs. Use official service manuals or parts catalogs for your product.

Be the first to comment

Leave a Reply

Your email address will not be published.