The Onan B48G is a 782 cc (47.7 cu-in) two cylinder air-cooled four-stroke internal combustion small gasoline engine with horizontal shaft manufactured by Onan for general-purpose applications.
The B48G engine has an L-head design with two flat cylinders; a carburetor fuel system, an automotive-type battery ignition system, and an electric starter.
The cylinder bore is 82.55 mm (3.25 in) and the piston stroke is 73.00 mm (2.87 in), the compression ratio rating is 7.0:1. The Onan B48G 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.
General information
| Engine Specifications | |
| Model | Onan B48G |
| Type | 4-stroke, L-head, flat |
| Displacement | 782 cm3 (47.7 cu-in) |
| Max. horsepower | 20.0 HP (14.9 kW) at 3,600 rpm |
| Max. torque | 43.0 N·m (4.4 kg·m, 31.7 ft·lb) |
| Carburetor | – |
| Cooling system | Forced-air |
| Ignition system | Automotive-type battery ignition system |
| Lubricating system | Forced lubrication |
| Starting system | Electric starter |
| PTO shaft rotation | Clockwise (viewed from flywhee) |
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 | 82.42-82.44 mm (3.2449-3.2457 in) | |
| Ring end gap | Top/Second | 0.250-0.510 mm (0.0098-0.0201 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 | |
| Valves: | 4 (2 per cylinder) | |
| Stem outer diameter (standard): | INTAKE | 8.700-8.710 mm (0.3425-0.3429 in) |
| EXHAUST | 8.660-8.670 mm (0.3409-0.3413 in) | |
| Valve spring free length: | 42.210 mm (1.6618 in) | |
| Camshaft journal diameter: | 34.900-34.910 mm (1.374-1.3744 in) | |
| Lobe height: | INTAKE | 29.570—29.720 mm (1.164—1.170 in) |
| EXHAUST | 29.440—29.590 mm (1.159—1.165 in) | |
Service Information
| Engine | |
| 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 (0.013 in) |
| Oil system | |
| Recommended oil | SAE 10W-30 |
| Oil capacity | With oil filter: 1.7 L (1.8 US. qt, 1.5 Imp. qt.) Without oil filter: 1.4 L (1.48 US. qt, 1.23 Imp. qt.) |
| 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) |
| Breaker point gap | Spec A&B: 0.530 mm (0.020 in) Spec C: 0.410 mm (0.016 in) |
Author:
This is awsome, thank you
Big help. Was looking for information on an Old (40 something) engine. Thanks