The Honda G42 is a 171 cc single-cylinder air-coolled 4-stroke internal combustion small gasoline engine manufactured by Honda Motor Company since 1972 for general-purpose applications.
The Honda G42 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.
The G42 engine a compression ratio rating is 6.4:1, cylinder bore and piston stroke are 66.0 mm (2.6 in) and 50.0 mm (2.0 in), respectively.
The G42 produced 3.3 PS (2.42 kW) at 3400 rpm of continuous rated horsepower and 4.5 PS (3.31 kW) at 4000 rpm of maximum horsepower.
General information
| Engine Specifications | |
| Model | G42 |
| Type | 4-stroke, side valve type (L-head), single cylinder |
| Displacement | 171 cm 3 (10.4 cu-in) |
| Max. horsepower | 4.5 PS (3.31 kW) at 4000 rpm |
| Max. torque | 8.3 Nm (0.85 kg·m) at 3600 rpm |
| Carburetor | Horizontal, butterfly valve |
| Cooling system | Forced-air |
| Ignition system | High voltage ignition |
| Lubricating system | Splash system |
| Starting system | Recoil starter |
| Stoping system | Ground switch |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| 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 consumption | 300 g/HPh (0.67 lb/HPh) |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
Dimensions and Weight
| G42 K1 | |
| Length, mm (in) | 425 (16.7) |
| Width, mm (in) | 325 (12.8) |
| Height, mm (in) | 430 (16.9) |
| Dry weight, kg (lb) | 19.0 (41.9) |
Cylinder Block and Head
| Cylinder block | ||
| Compression ratio: | 6.4:1 | |
| Bore x Stroke | 66 x 50 mm (2.6 in x 2.0 in in) | |
| Sleeve internal diameter | 66.00 mm (2.59 in) | |
| Piston skirt outer diameter | 65.97-65.99 mm (2.59-2.60 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Ring side clearance | Top/second/oil | 0.03-0.07 mm (0.001-0.003 in) |
| Ring end gap | Top/second/oil | 0.2-0.4 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 | |
| Stem outer diameter (standard): | INTAKE | 6.970 mm (0.274 in) |
| EXHAUST | 6.925 mm (0.272 in) | |
| Guide internal diameter | INTAKE / EXHAUST | 7.000 mm (0.276 in) |
| Spring free length | 27.9 mm (1.1 in) | |
| Camshaft journal diameter: | 11.953-11.968 mm (0.470-0.471 in) | |
Maintenance data
| Engine | |
| Cylinder compression | 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 l (0.6 US gal. 0.5 Imp. gal.) |
| Ignition system | |
| Spark plug | G42 – NGK: B-6HS G42K1 – 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:
Need a linkage diagram for the Honda G42 general purpose engine.
Looking for parts or new carburetor for this engine. Any chance you could help me??
Have you found a new carb?
I have a Honda g42 for sale soon on gumtree and ebay
I am needing a new coil , will others fit as can’t find any listed for g42