The Honda GX100 is a 98 cc (5.98 cu·in) natural aspirated single-cylinder four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, manufactured by Honda Motor Company for general-purpose applications.
A 56.0 mm (2.2 in) cylinder bore and 40.0 mm (1.57 in) piston stroke give the GX100 engine a total of 98 cc of displacement. The compression ratio rating is 8.5:1.
The Honda GX100 engine produced 3.0 PS (2.2 kW; 3.0 HP) at 3,600 rpm of maximum output power and 5.7 N·m (0.6 kg·m, 4.2 ft·lb) at 3,600 rpm of peak torque.
The Honda GX100 features:
- Overhaed camshaft OHC design
- Transistorized magneto ignition system
- Horizontal type carburetor with butterfly valve
- Centrifugal governor
- Splash lubrication system
- Forced air cooling system
- Recoil starter
General information
| Engine Specifications | |
| Engine model | GX100 |
| Engine type | 4-stroke, OHC, single-cylinder |
| Displacement | 98 cm3, (5.98 cu·in) |
| Max. horsepower | 3.0 PS (2.2 kW; 3.0 HP) at 3,600 rpm |
| Max. torque | 5.7 N·m (0.6 kg·m, 4.2 ft·lb) at 3,600 rpm |
| Cooling system | Forced air |
| Air cleaner | Dual-element type |
| Lubricating system | Splash |
| Ignition system | Transistorized magneto ignition |
| Fuel system | Horizontal type carburetor with butterfly valve |
| Fuel consumption | 240 g/PSh |
| Fuel tank capacity | 1.2 L (0.32 US. gal. 0.26 Imp. gal.) |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Starting system | Recoil starter |
| Stoping system | Ignition primary circuit ground |
| Governor | Centrifugal governor |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
| Dimensions (L x W X H) | – |
| Dry weight | – |
Cylinder Block and Head
| Cylinder block | |
| Compression ratio: | 8.5:1 |
| Cylinder bore: | 56.0 mm (2.2 in) |
| Piston stroke: | 40.0 mm (1.57 in) |
| Cylinder internal diameter (standard): | 56.000 mm (2.2047 in) |
| Piston skirt outer diameter (standard): | 55.965-55.985 mm (2.2033-2.2041 in) |
| Number of piston rings (compression / oil): | 2/1 |
| Connecting rod small end diameter (standard): | 13.005-13.020 mm (0.512-0.5126 in) |
| Side clearance (Top): | 0.015-0.050 mm (0.0006-0.002 in) |
| Side clearance (Second): | 0.015-0.050 mm (0.0006-0.002 in) |
| Side clearance (Oil): | 0.015-0.050 mm (0.0006-0.002 in) |
| Ring end gap (Top): | 0.150-0.300 mm (0.0059-0.0118 in) |
| Ring end gap (Second): | 0.300-0.450 mm (0.0118-0.0177 in) |
| Crankpin journal diameter: | 23.970-23.980 mm (0.9437-0.9441 in) |
| Crankshaft center distance: | 20 mm (0.785 in) |
| Cylinder head | |
| Valve arrangement: | OHC |
| Valves: | 2 |
| Valve steam diameter (INTAKE): | 3.970-3.985 mm (0.1563-0.1569 in) |
| Valve steam diameter (EXHAUST): | 3.935-3.950 mm (0.1549-0.1555 in) |
| Valve spring free length (INTAKE): | 25.800 mm (1.0157 in) |
| Valve spring free length (EXHAUST): | 25.800 mm (1.0157 in) |
| Camshaft lobe height (INTAKE): | 36.483 mm (1.4363 in) |
| Camshaft lobe height (EXHAUST): | 36.483 mm (1.4363 in) |
Tightening torque
| Tightening torque specs | |
| Connecting rod bolt | 5 Nm; 0.5 kg·m; 3.6 ft·lb |
| Oil dran plug bolt | 18 Nm; 1.8 kg·m; 13 ft·lb |
| Valve adjusting lock nut | 7.5 Nm; 0.75 kg·m; 5.4 ft·lb |
| Flywheel nut | 42 Nm; 4.3 kg·m; 31 ft·lb |
| Governor arm nut | 10 Nm; 1.0 kg·m; 7 ft·lb |
| Stopper plate screw | 1 Nm; 0.1 kg·m; 0.7 ft·lb |
| Spark plug | 11.8 Nm; 1.2 kg·m; 8.7 ft·lb |
Service Data
| Engine | |
| Maximum speed: | 4,000 ± 200 rpm |
| Idle speed: | 1,550 ± 150 rpm |
| Cylinder compression: | 5.0 kg/cm2 (71 psi) at 700 rpm |
| Valve clearance | |
| Intake valve | 0.15 ± 0.04 mm (0.006 ± 0.002 in) |
| Exhaust valve | 0.20 ± 0.04 mm (0.008 ± 0.002 in) |
| Oil system | |
| Lubrication system: | Splash |
| Oil type: | Honda 4-stroke or an equivalent (SE or SF) |
| Recommended oil: | SAE 10W-30 |
| Oil capacity: | 0.4 L (0.42 US. qt, 0.35 Imp. qt.) |
| Fuel system | |
| Type: | Horizontal type carburetor with butterfly valve |
| Main jet: | #60 |
| Float height: | 12 mm mm (0.4724 in) |
| Pilot screw opening: | 2-3/8 turns out |
| Ignition system | |
| Type: | Transistorized magneto ignition |
| Spark plug: | NGK: CR5HSB DENSO: U16FSR-UB |
| Spark plug gap: | 0.7-0.8 mm (0.0276-0.0315 in) |
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