Onan B43E

Onan B43EThe Onan B43E is a 710 cc (43.3 cu-in) two cylinder air-cooled four-stroke internal combustion small gasoline engine with horizontal shaft manufactured by Onan for general-purpose applications.

The B43E engine has an L-head design with two flat cylinders; carburetor fuel system and electric starter.

The cylinder bore is 82.55 mm (3.25 in) and the piston stroke is 66.55 mm (2.62 in), the compression ratio rating is 6.2:1. The Onan B43E engine produced 16.2 PS (11.9 kW; 16.0 HP) at 3,600 rpm of horsepower and 44.0 N·m (4.5 kg·m, 32.4 ft·lb) of torque.

General information

Engine Specifications
ModelOnan B43E
Type4-stroke, L-head, flat
Displacement710 cm3 (43.3 cu-in)
Max. horsepower16.0 HP (11.9 kW) at 3,600 rpm
Max. torque44.0 N·m (4.5 kg·m, 32.4 ft·lb)
Cooling systemForced-air
Ignition system
Lubricating systemForced lubrication
Starting systemElectric starter
PTO shaft rotationClockwise (viewed from flywhee)

Cylinder Block and Head

Cylinder block
Compression ratio:6.2:1
Bore x Stroke82.55 X 66.55 mm (3.25 x 2.62 in)
Sleeve internal diameter82.530-82.550 mm (3.2492-3.25 in)
Piston skirt outer diameter82.42-82.44 mm (3.2449-3.2457 in)
Ring end gapTop/Second0.250-0.510 mm (0.0098-0.0201 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
Valves:4 (2 per cylinder)
Stem outer diameter (standard):INTAKE8.700-8.710 mm (0.3425-0.3429 in)
EXHAUST8.660-8.670 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:INTAKE28.370-28.470 mm (1.1169-1.1209 in)
EXHAUST28.370-28.470 mm (1.1169-1.1209 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 (0.013 in)
Oil system
Recommended oilSAE 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 timing16° B.T.D.C.
Spark plugNGK BPR5EF, Champion RS14YC
Spark plug gap0.640 mm (0.0252 in)
Breaker point gap0.410 mm (0.01610.0161 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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