The Onan B43G is a 0.7 L (710 cc, 43.33 cu·in) two cylinders natural aspirated 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 66.55 mm (2.62 in), respectively. The compression ratio rating is 6.5:1.
This engine produced 18.2 PS (13.4 kW; 18.0 HP) at 3,600 rpm of horsepower and 43.0 N·m (4.4 kg·m, 31.7 ft·lb) of torque.
The Onan B43G features:
- L-head design
- Automotive type battery ignition system
- Carburetor type fuel system
- Forced lubrication lubrication system
- Air cooling system
- Electric starter
General information
| Engine Specifications | |
| Engine model | B43G |
| Engine type | 4-stroke, L-head, |
| Displacement | 710 cm3, (43.33 cu·in) |
| Max. horsepower | 18.2 PS (13.4 kW; 18.0 HP) at 3,600 rpm |
| Max. torque | 43.0 N·m (4.4 kg·m, 31.7 ft·lb) |
| Cooling system | Forced air |
| Air cleaner | – |
| Lubricating system | Forced lubrication |
| Ignition system | Automotive type battery ignition system |
| Fuel system | Carburetor |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Starting system | Electric starter |
| Stoping system | Ignition primary circuit ground |
| Dimensions (L x W X H) | – |
| Dry weight | – |
Cylinder Block and Head
| Cylinder block | |
| Compression ratio: | 6.5:1 |
| Cylinder bore: | 82.55 mm (3.25 in) |
| Piston stroke: | 66.55 mm (2.62 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: | 33.275 mm (1.31 in) |
| Cylinder head | |
| Valve arrangement: | L-head, gear driven |
| Valves: | 2 |
| 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): | 28.370-28.470 mm (1.1169-1.1209 in) |
| Camshaft lobe height (EXHAUST): | 29.570—29.720 mm (1.1640—1.1700 in.) |
| Camshaft journal diameter: | 29.440—29.590 mm (1.1590—1.1650 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: | 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.) |
| Fuel system | |
| Type: | Carburetor |
| Ignition system | |
| Type: | Automotive type battery ignition system |
| Ignition timing: | 16° B.T.D.C. |
| Spark plug: | NGK BPR5EF, Champion RS14YC |
| Spark plug gap: | 0.640 mm (0.0252 in) |
| Ignition coil air gap | 0.410 mm (0.0161 in) |
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