Honda G100

Honda G100The Honda G100 is a 76 cc, (4.64 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 1980 for general-purpose applications.

The Honda G100 engine has a single-cylinder, side-valve (L-head) design with two valves, a camshaft driven by a single-row chain, and a heavy-duty recoil starter. This engine used a horizontally type carburetor with butterfly valve, flywheel magneto ignition, splash type lubricating system, and forced-air cooling system. The G100 is equipped with a 1.4 L (0.37 US. gal. 0.31 Imp. gal.) fuel tank.

The G100 engine produced 2.0 PS (1.5 kW; 2.0 HP) or 2.2 PS (1.6 kW; 2.1 HP) at 4,200 rpm of maximum horsepower and 3.3 N·m (0.3 kg·m, 2.4 ft·lb) or 3.5 N·m (0.4 kg·m, 2.6 ft·lb) of peak torque.

General information

Engine Specifications
Engine modelG100
Engine type4-stroke, L-head, single-cylinder
Displacement76 cm3, (4.64 cu·in)
Max. horsepower 2.0 PS (1.5 kW; 2.0 HP)
or 2.2 PS (1.6 kW; 2.1 HP) at 4,200 rpm
Max. torque 3.3 N·m (0.3 kg·m, 2.4 ft·lb)
or 3.5 N·m (0.4 kg·m, 2.6 ft·lb)
Cooling systemForced air
Lubricating systemSplash type
Ignition systemFlywheel magneto
Fuel systemHorizontal carburetor with butterfly valve
Fuel consumption320 g/HPh
Fuel tank capacity1.4 L (0.37 US. gal. 0.31 Imp. gal.)
Fuel usedUnleaded gasoline (octane number 86 or higher)
Starting systemRecoil starter
Stoping systemIgnition primary circuit ground
GovernorCentrifugal govervor
PTO shaft rotationCounterclockwise (from PTO shaft side)

Cylinder Block and Head

It has a 46.0 mm (1.81 in) cylinder bore and a 46.0 mm (1.81 in) piston stroke. The compression ratio rating is 6.5:1.

Cylinder block
Compression ratio:6.5:1
Cylinder bore:46.0 mm (1.81 in)
Piston stroke:46.0 mm (1.81 in)
Cylinder internal diameter (standard):46.000 mm (1.811 in)
Piston skirt outer diameter (standard):45.980 mm (1.8102 in)
Number of piston rings (compression / oil):2/1
Connecting rod big end diameter (standard):18.000 mm (0.7087 in)
Connecting rod small end diameter (standard):10.000 mm (0.3937 in)
Side clearance (Top):0.025-0.055 mm (0.001-0.0022 in)
Side clearance (Second):0.010-0.040 mm (0.0004-0.0016 in)
Side clearance (Oil):0.010-0.040 mm (0.0004-0.0016 in)
Ring end gap (Top):0.15-0.35 mm (0.0059-0.0138 in)
Ring end gap (Second):0.15-0.35 mm (0.0059-0.0138 in)
Ring end gap (Oil):0.15-0.35 mm (0.0059-0.0138 in)
Crankpin journal diameter:17.973 mm (0.7076 in)
Crankshaft center distance:23.0 mm (0.905 in)
Cylinder head
Valve arrangement:L-head
Valve steam diameter (INTAKE):5.490 mm (0.2161 in)
Valve steam diameter (EXHAUST):5.445 mm (0.2144 in)
Valve spring free length (INTAKE):27.1 mm (1.0669 in)
Valve spring free length (EXHAUST):27.1 mm (1.0669 in)
Camshaft lobe height (INTAKE):18.100-18.400 mm (0.7126-0.7244 in)
Camshaft lobe height (EXHAUST):18.100-18.400 mm (0.7126-0.7244 in)

Tightening torque

Tightening torque settings
Carburetor4-6 Nm; 0.4-0.6 kg·m; 2.9-4.3 ft·lb;
Flywheel45-55 Nm; 4.5-5.5 kg·m; 32.5-40 ft·lb;
Governor arm8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb;
Cylinder head8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb;
Crankcase cover8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb;
5 mm bolts, nuts4-7 Nm; 0.4-0.7 kg·m; 2.9-5.1 ft·lb
6 mm bolts, nuts8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
8 mm bolts, nuts20-28 Nm; 2.0-2.8 kg·m; 14.5-20.3 ft·lb
10 mm bolts, nuts35-40 Nm; 3.5-4.0 kg·m; 25-29 ft·lb

Service Data

Idle speed:1,400 rpm
Cylinder compression:6.5 kg/cm2 (637 kPa) at 800 rpm
Valve clearance
Intake valve clearance:0.08-0.16 mm (0.0031-0.0063 in)
Exhaust valve clearance:0.08-0.16 mm (0.0031-0.0063 in)
Oil system
Lubrication system:Splash type
Oil type:10W-40
Recommended oil:Honda 4-stroke “SE”
Oil capacity:0.45 L (0.48 US. qt, 0.4 Imp. qt.)
Fuel system
Type:Horizontal carburetor with butterfly valve
Main jet:#55
Float height:6.7-9.7 mm mm (0.2638 in)
Pilot screw:1-3/8 turns out
Ignition system
Type:Flywheel magneto
Ignition timing:20° B.T.D.C. (Fixed)
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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