Honda G25

Honda G25 engineThe Honda G25 is a 59 cc (3.6 cu·in) natural aspirated single-cylinder four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, manufactured by Honda Motor Company since 1966 for general-purpose applications.

The Honda G25 engine has a single-cylinder, an efficient combustion chamber, and a heavy-duty recoil starter. This engine used a horizontal type carburetor with a butterfly valve, high-voltage ignition, splash type lubricating system, and forced-air cooling system. The G25 is equipped with a 2.0 L fuel tank.

The G25 engine produced 2.5 PS (1.86 kW; 2.5 HP) at 6,000 rpm of maximum horsepower and 1.8 PS (1.32 kW; 1.8 HP) at 5,000 rpm of continuous horsepower.

General information

Engine Specifications
Engine modelG25
Engine type4-stroke, OHV, single-cylinder
Displacement59 cm3, (3.6 cu·in)
Max. horsepower2.5 PS (1.86 kW; 2.5 HP) at 6,000 rpm
Max. torque
Cooling systemForced air
Lubricating systemSplash type
Ignition systemHigh-voltage ignition
Fuel systemHorizontal type carburetor with butterfly valve
Fuel tank capacity2.0 L (0.53 US. gal. 0.44 Imp. gal.)
Fuel usedUnleaded gasoline (octane number 86 or higher)
Starting systemRecoil starter
Stoping systemIgnition primary circuit ground
PTO shaft rotationCounterclockwise (from PTO shaft side)
Dimensions (L x W X H)360 x 282 x 276 mm (14.2 x 11.1 x 10.9 in)
Dry weight13.8 kg (30.4 lbs)

Cylinder Block and Head

Cylinder bore and piston stroke are 46.0 mm (1.81 in) and 35.6 mm (1.4 in), respectively. Compression ratio rating is 8.6:1. Friction components such as the cylinder sleeve and piston are made of high strength materials. The crankshaft is mounted on two ball bearings for reduced friction.

Cylinder block
Compression ratio:8.6:1
Cylinder bore:46.0 mm (1.81 in)
Piston stroke:35.6 mm (1.4 in)
Number of piston rings (compression / oil):2 / 1
Crankshaft center distance:17.8 mm (0.7 in)
Cylinder head

Service Data

Oil system
Lubrication system:Splash type
Oil type:SAE 10W-30 or 10W-40
Recommended oil:Honda 4-stroke or an equivalent
Oil capacity:0.74 L (0.78 US. qt, 0.65 Imp. qt.)
Fuel system
Type:Horizontal type carburetor with butterfly valve
Ignition system
Type:High-voltage ignition
Spark plug:NGK: C-6HB
Spark plug gap:0.6-0.7 mm (0.0236-0.0276 in)


Manufacturer or BrandModels
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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We try to use official documentation and verify the published data, but errors may occur. In addition, specifications of machinery and equipment may vary depending on markets and modifications. We do not recommend the use of this data for spare parts or repairs. Use official service manuals or parts catalogs for your product.

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