The Honda G50 is a 187 cc (11.4 cu-in) single-cylinder, air-cooled, four-stroke, internal combustion small gasoline engine manufactured by Honda Motor Company for general-purpose applications.
The Honda G50 engine has a slide valve (L-head) design and camshaft driven by a single row chain driven by the crankshaft. It has a recoil starter, horizontal carburetor with butterfly valve and high voltage ignition.
Cylinder bore and piston stroke are 69.0 mm (2.7 in) and 50.0 mm (2.0 in), respectively. Compression ratio rating is 6.5:1 for G50K1 and 6.9:1 for G50K2
The Honda G50 engine produced 3.8 PS (2.8 KW; 3.8 HP) at 3,600 rpm of continuous rated horsepower and 5.0 PS (3.67 KW; 4.9 HP) at 4,000 rpm of maximum horsepower. This engine produced 9.0 Nm (0.92 kg·m; 6.64 lbf·ft) at 3,600 rpm of torque.
General information
| Engine Specifications | |
| Model | G50 |
| Type | 4-stroke, side valve type (L-head), single cylinder |
| Displacement | 187 cm 3 (11.4 cu-in) |
| Max. horsepower | 5.0 PS (3.67 KW; 4.9 HP) at 4,000 rpm |
| Max. torque | 9.0 Nm (0.92 kg·m; 6.64 lbf·ft) at 3,600 rpm |
| Carburetor | Horizontal, butterfly valve |
| Cooling system | Forced-air |
| Ignition system | High voltage ignition |
| Lubricating system | Splash type |
| Starting system | Recoil starter |
| Stoping system | Ground switch |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Fuel tank capacity | G50 – 6.0 liters (1.6 US gal. 1.3 Imp. gal.) G50K1 – 3.4 liters (0.9 US gal. 0.7 Imp. gal.) G50K2 – 4.0 liters (1.1 US gal. 0.9 Imp. gal.) |
| Fuel consumption | 300 g/HPh (0.67 lb/HPh) |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
Cylinder Block and Head
| Cylinder block | ||
| Compression ratio: | G50K1 – 6.5:1 G50K2 – 6.9:1 |
|
| Bore x Stroke | 69 x 50 mm (2.7 in x 2.0 in in) | |
| Sleeve internal diameter | 69.00 mm (2.71 in) | |
| Piston skirt outer diameter | 68.97-68.99 mm (2.5492-2.5558 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Piston ring side clearance (Top): | 0.02-0.06 mm (0.008-0.024 in) | |
| Piston ring side clearance (Second): | 0.02-0.06 mm (0.008-0.024 in) | |
| Piston ring side clearance (Oil): | 0.02-0.06 mm (0.008-0.024 in) | |
| Piston ring end gap (Top): | 0.200-0.400 mm (0.008-0.016 in) | |
| Piston ring end gap (Second): | 0.200-0.400 mm (0.008-0.016 in) | |
| Piston ring end gap (Oil): | 0.200-0.400 mm (0.008-0.016 in) | |
| Connecting rod small end ID | 18.01-18.03 mm (0.708-0.711 in) | |
| Cylinder Head | ||
| Warpage (limit) | 0.10 mm (0.004 in) | |
| Valve Arrangement: | Side valve type (L-head) | |
| Valves: | 2 | |
| Valve stem outer diameter (INTAKE): | 6.970 mm (0.274 in) | |
| Valve stem outer diameter (EXHAUST): | 6.925 mm (0.272 in) | |
| Valve guide inner diameter (INTAKE): | 7.000 mm (0.276 in) | |
| Valve guide inner diameter (EXHAUST): | 7.000 mm (0.276 in) | |
| Spring free length | 27.9 mm (1.1 in) | |
| Camshaft journal diameter: | 11.966-11.984 mm (0.4711-0.4718 in) | |
| Engine | |
| Cylinder compression | G50K1 – 7.0 kg/cm2 at 750 rpm G50K2 – 6.0 kg/cm2 at 1000 rpm |
| Adjust timing ignition | |
| Ignition timing | 20° B.T.D.C. (Fixed) |
| Adjust valve clearance | |
| Intake valve | 0.07 mm (0.003 in) |
| Exhaust valve | 0.07 mm (0.003 in) |
| Oil system | |
| Oil type | Honda 4-stroke |
| Recommended oil | 10W-40 |
| Oil capacity | 0.6 liters (0.6 US gal. 0.5 Imp. gal.) |
| Ignition system | |
| Spark plug |
G50 – NGK: B-6H G50K1 – NGK: B-6HS G50K2 – NGK: B-6HS, BR-6HS |
| Spark plug gap | 0.6-0.7 mm (0.024-0.028 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 |
Author:
Needs more pictures of the engine from all sides and the picture of the petrol tank from the top please.
es varu nosūtīt
I would like to know what setting is by spec for the carb screw 1 and a half turns or what hope to hear back .I built a moped with this motor on a bycycles and it’s awsume to ride
I have one of these but it on a genarator I need a new coil with built in cap. For the motor
lo hai trovato?
forse anche io…
i am looking for a diaphram for the carb
Managed to repaor mine with a bike tube repairkit… works since 8 yrs. But also interested in a new one