The 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-head 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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