The Honda G42 is a 171 cc (10.4 cu-in) single-cylinder, air-cooled, four-stroke cycle, 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; 3.2 HP) at 3,400 rpm of continuous rated horsepower, 4.5 PS (3.31 KW; 4.4 HP) at 4,000 rpm of maximum horsepower and 8.3 Nm (0.85 kg·m; 6.13 lbf·ft) at 3,600 rpm of peak torque.
General information
| Engine Specifications | |
| Model | G42 |
| Type | 4-stroke, sidevalve type (L-head), single cylinder |
| Displacement | 171 cm 3 (10.4 cu-in) |
| Max. horsepower | 4.5 PS (3.31 KW; 4.4 HP) at 4,000 rpm |
| Max. torque | 8.3 Nm (0.85 kg·m; 6.13 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 | G42: 3.4 liters (0.9 US gal, 0.7 Imp. gal) G42K1: 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) |
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 | |
| Piston ring side clearance (Top): | 0.030-0.070 mm (0.001-0.003 in) | |
| Piston ring side clearance (Second): | 0.030-0.070 mm (0.001-0.003 in) | |
| Piston ring side clearance (Oil): | 0.030-0.070 mm (0.001-0.003 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: | 11.953-11.968 mm (0.470-0.471 in) | |
Maintenance data
| Engine | |
| Cylinder compression | 6.0 kg/cm2 at 1,000 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 (0.63 US.qts, 0.53 Imp. qts) |
| 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 |
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