Honda G50

Honda G50The Honda G50 is a 187 cc, (11.4 cu·in) natural aspirated single-cylinder four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, manufactured by Honda Motor Company for general-purpose applications.

The cylinder bore is 69.0 mm (2.72 in) and the piston stroke is 50.0 mm (1.97 in). The compression ratio rating is 6.5:1 for the G50K1 version or 6.9:1 for the Honda G50K2.

The G50 engine produced 3.8 PS (2.8 kW; 3.8 HP) at 3,600 rpm of continuous rated horsepower or 5.0 PS (3.67 kW; 4.9 HP) at 4,000 rpm of maximum output power and 9.0 N·m (0.9 kg·m, 6.6 ft·lb) at 3,600 rpm of maximum torque.

The Honda G50 features:

  • L-haed design
  • High voltage ignition system
  • Horizontal type carburetor with butterfly valve
  • Centrifugal govervor
  • Splash type lubrication system
  • Forced air cooling system
  • Recoil starter

General information

Engine Specifications
Engine model G50
Engine type 4-stroke, L-head, single-cylinder
Displacement 187 cm3, (11.4 cu·in)
Max. horsepower 5.0 PS (3.67 kW; 4.9 HP) at 4,000 rpm
Max. torque 9.0 N·m (0.9 kg·m, 6.6 ft·lb) at 3,600 rpm
Cooling system Forced air
Air cleaner Oil bath type
Lubricating system Splash
Ignition system High voltage ignition
Fuel system Horizontal type carburetor with butterfly valve
Fuel consumption 300 g/HPh
Fuel tank capacity G50: 6.0 L (1.6 US gal. 1.3 Imp. gal.)
G50K1: 3.4 L (0.9 US gal. 0.7 Imp. gal.)
G50K2: 4.0 L (1.1 US gal. 0.9 Imp. gal.)
Fuel used Unleaded gasoline (octane number 86 or higher)
Starting system Recoil starter
Stoping system Ignition primary circuit ground
Governor Centrifugal govervor
PTO shaft rotation Counterclockwise (from PTO shaft side)
Dimensions (L x W X H)
Dry weight

Cylinder Block and Head

Cylinder block
Compression ratio: G50K1: 6.5:1
G50K2: 6.9:1
Cylinder bore: 69.0 mm (2.72 in)
Piston stroke: 50.0 mm (1.97 in)
Cylinder internal diameter (standard): 69.000 mm (2.7165 in)
Piston skirt outer diameter (standard): 68.970-68.990 mm (2.7153-2.7161 in)
Number of piston rings (compression / oil): 2/1
Connecting rod small end diameter (standard): 18.010-18.030 mm (0.7091-0.7098 in)
Side clearance (Top): 0.020-0.060 mm (0.0008-0.0024 in)
Side clearance (Second): 0.020-0.060 mm (0.0008-0.0024 in)
Side clearance (Oil): 0.020-0.060 mm (0.0008-0.0024 in)
Ring end gap (Top): 0.200-0.400 mm (0.0079-0.0157 in)
Ring end gap (Second): 0.200-0.400 mm (0.0079-0.0157 in)
Ring end gap (Oil): 0.200-0.400 mm (0.0079-0.0157 in)
Cylinder head
Valve arrangement: L-head
Valves: 2
Valve steam diameter (INTAKE): 6.970 mm (0.2744 in)
Valve steam diameter (EXHAUST): 6.925 mm (0.2726 in)
Valve spring free length (INTAKE): 27.9 mm (1.0984 in)
Valve spring free length (EXHAUST): 27.9 mm (1.0984 in)
Camshaft journal diameter : 11.966-11.984 mm (0.4711-0.4718 in)

Tightening torque specs

Tightening torque specs
Cylinder head (8×1.25 mm) 20-24 Nm; 2.0-2.4 kg·m; 14.5-17.4 ft·lb
Flywheel (14×1.25 mm) 80-90 Nm; 8.0-9.0 kg·m; 57.9-65.1 ft·lb
Fuel tank (6×1.0 mm) 10-12 Nm; 1.0-1.2 kg·m; 7.2-8.7 ft·lb
Fuel tank (8×1.25 mm) 24-28 Nm; 2.4-2.8 kg·m; 17.4-20.3 ft·lb
Muffler (6×1.0 mm) 8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
Starter pulley (6×1.0 mm) 8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
Fuel cock (6×1.0 mm) 10-12 Nm; 1.0-1.2 kg·m; 7.2-8.7 ft·lb
PTO (8×1.25 mm) 20-24 Nm; 2.0-2.4 kg·m; 14.5-17.4 ft·lb
Carburetor (6×1.0 mm) 10-12 Nm; 1.0-1.2 kg·m; 7.2-8.7 ft·lb
Others
5×0.8 mm screw, bolt, nut 3.5-6.5 Nm; 0.35-0.65 kg·m; 2.5-4.7 ft·lb
6×1.0 mm bolt 8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
8×1.25 mm bolt 20-28 Nm; 2.0-2.8 kg·m; 14.5-20.3 ft·lb
10×1.25 mm bolt 40-50 Nm; 4.0-5.0 kg·m; 28.9-36.2 ft·lb

Service Data

Cylinder compression: G50K1: 7.0 kg/cm2 at 750 rpm
G50K2: 6.0 kg/cm2 at 1,000 rpm
Valve clearance
Intake valve clearance: 0.07 mm (0.0028 in)
Exhaust valve clearance: 0.07 mm (0.0028 in)
Oil system
Lubrication system: Splash
Oil type: 4-stroke Honda engine oil
Recommended oil: SAE 10W-40
Oil capacity: 0.6 L (0.63 US. qt, 0.53 Imp. qt.)
Fuel system
Type: Horizontal type carburetor with butterfly valve
Fuel tank capacity G50: 6.0 L (1.6 US gal. 1.3 Imp. gal.)
G50K1: 3.4 L (0.9 US gal. 0.7 Imp. gal.)
G50K2: 4.0 L (1.1 US gal. 0.9 Imp. gal.)
Ignition system
Type: High voltage ignition
Ignition timing: 20° B.T.D.C. (Fixed)
Spark plug: G50: NGK B-6H
G50K1: – NGK B-6HS
G50K2: – NGK B-6HS, BR-6HS
Spark plug gap: 0.6-0.7 mm (0.0236-0.0276 in)

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