The Honda G42 is a 171 cc, (10.44 cu·in) natural aspirated single-cylinder four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, manufactured by Honda Motor Company from 1972 for general-purpose applications.
The Honda G42 engine has a single-cylinder, slide valve (L-head) design, and camshaft driven by a single row chain driven by the crankshaft. It used a recoil starter, horizontal carburetor with butterfly valve, and high voltage ignition system. The engine is fitted with an oil bath-type air cleaner and a 3.4 L (0.9 US. gal. 0.75 Imp. gal.) fuel tank.
The G42 engine produced 3.3 PS (2.42 kW; 3.2 HP) at 3,400 rpm of continuous rated power, 4.5 PS (3.3 kW; 4.4 HP) at 4,000 rpm of maximum horsepower, and 8.3 N·m (0.8 kg·m, 6.1 ft·lb) at 3,600 rpm of peak torque.
General information
| Engine Specifications | |
| Engine model | G42 |
| Engine type | 4-stroke, L-head, single-cylinder |
| Displacement | 171 cm3, (10.44 cu·in) |
| Max. horsepower | 4.5 PS (3.3 kW; 4.4 HP) at 4,000 rpm |
| Max. torque | 8.3 N·m (0.8 kg·m, 6.1 ft·lb) at 3,600 rpm |
| Cooling system | Forced air |
| Air cleaner | Oil bath type |
| Lubricating system | Splash type |
| Ignition system | High-voltage ignition |
| Fuel system | Horizontal type carburetor with butterfly valve |
| Fuel consumption | 300 g/HPh |
| Fuel tank capacity |
G42 – 3.4 L (0.9 US gal. 0.7 Imp. gal.) G42K1 – 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) | 425 x 325 x 430 mm (16.7 x 12.8 x 16.9 in) |
| Dry weight | 19.0 kg (41.9 lbs) |
Cylinder Block and Head
It has a 66.0 mm (2.6 in) cylinder bore and 50.0 mm (1.97 in) piston stroke. The compression ratio rating is 6.4:1.
| Cylinder block | |
| Compression ratio: | 6.4:1 |
| Cylinder bore: | 66.0 mm (2.6 in) |
| Piston stroke: | 50.0 mm (1.97 in) |
| Cylinder internal diameter (standard): | 66.000 mm (2.5984 in) |
| Piston skirt outer diameter (standard): | 65.970-65.980 mm (2.5972-2.5976 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) |
| Piston pin diameter: | 17.994-18.000 mm (0.7084-0.7087 in) |
| Side clearance (Top): | 0.030-0.070 mm (0.0012-0.0028 in) |
| Side clearance (Second): | 0.030-0.070 mm (0.0012-0.0028 in) |
| Side clearance (Oil): | 0.030-0.070 mm (0.0012-0.0028 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 lobe lift (INTAKE): | 5.8 mm (0.2283 in) |
| Camshaft lobe liift (EXHAUST): | 5.8 mm (0.2283 in) |
| Camshaft journal diameter: | 11.953-11.968 mm (0.4706-0.4712 in) |
Service Data
The Honda 4-stroke or an equivalent oil with a viscosity of SAE 10W-30 or 10W-40 is recommended for the Honda G42 engine, refilling oil capacity is 0.6 L (0.63 US. qt, 0.53 Imp. qt.).
| Compression pressure | |
| Standard: | 0.6 kg/cm2 |
| 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 type |
| Oil type: | SAE 10W-30 or 10W-40 |
| Recommended oil: | Honda 4-stroke or an equivalent |
| Oil capacity: | 0.6 L (0.63 US. qt, 0.53 Imp. qt.) |
| Fuel system | |
| Type: | Horizontal type carburetor with butterfly valve |
| Ignition system | |
| Type: | High-voltage ignition |
| Ignition type: | 20° B.T.D.C. |
| Spark plug: |
G42 – NGK: B-6HS G42K1 – NGK: B-6HS, BR-6HS |
| Spark plug gap: | 0.6-0.7 mm (0.0236-0.0276 in) |
Applications
| Manufacturer or Brand | Models |
| Tillers | |
| Honda | F42 |
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