The Honda GX120 T1 is a 118 cc (7.2 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.
Cylinder bore and piston stroke are 60.0 mm (2.36 in) and 42.0 mm (1.65 in), respectively. The compression ratio rating is 7.5:1 or 8.5:1.
The Honda GX120 T1 engine produced 3.9 PS (2.9 kW; 3.9 HP) at 4,000 rpm of maximum output power and 7.5 N·m (0.8 kg·m, 5.5 ft·lb) at 2,500 rpm of peak torque.
The Honda GX120 T1 features:
- Overhaed valve (OHV) 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 | GX120 T1 |
| Engine type | 4-stroke, OHV, single-cylinder |
| Displacement | 118 cm3, (7.2 cu·in) |
| Max. horsepower | 3.9 PS (2.9 kW; 3.9 HP) at 4,000 rpm |
| Max. torque | 7.5 N·m (0.8 kg·m, 5.5 ft·lb) at 2,500 rpm |
| Cooling system | Forced air |
| Air cleaner | Dual elemenet type Semi-dry type Oil bath type Cyclone type |
| Lubricating system | Splash type |
| Ignition system | Transistorized magneto ignition |
| Fuel system | Horizontal type carburetor with butterfly valve |
| Fuel consumption | 230 g/PSh |
| Fuel tank capacity | 2.5 L (0.66 US. gal. 0.55 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: | 7.5:1 or 8.5:1 |
| Cylinder bore: | 60.0 mm (2.36 in) |
| Piston stroke: | 42.0 mm (1.65 in) |
| Cylinder internal diameter (standard): | 60.000 mm (2.3622 in) |
| Piston skirt outer diameter (standard): | 59.985 mm (2.3616 in) |
| Number of piston rings (compression / oil): | 2/1 |
| Connecting rod big end diameter (standard): | 26.020 mm (1.0244 in) |
| Connecting rod small end diameter (standard): | 13.005 mm (0.512 in) |
| Piston pin diameter: | 13.000 mm (0.5118 in) |
| Side clearance (Top): | 0.015-0.045 mm (0.0006-0.0018 in) |
| Side clearance (Second): | 0.015-0.045 mm (0.0006-0.0018 in) |
| Side clearance (Oil): | 0.015-0.045 mm (0.0006-0.0018 in) |
| Ring end gap (Top): | 0.200-0.400 mm (0.0079-0.0157 in) |
| Ring end gap (Second): | 0.200-0.400 mm (0.0079-0.0157 in) |
| Ring end gap (Oil): | 0.150-0.350 mm (0.0059-0.0138 in) |
| Ring width (Top): | 1.500 mm (0.0591 in) |
| Ring width (Second): | 1.500 mm (0.0591 in) |
| Ring width (Oil): | 2.500 mm (0.0984 in) |
| Crankpin journal diameter: | 25.980 mm (1.0228 in) |
| Crankshaft center distance: | 21.000 mm (0.825 in) |
| Cylinder head | |
| Valve arrangement: | OHV |
| Valves: | 2 |
| Valve spring free length (INTAKE): | 30.500 mm (1.2008 in) |
| Valve spring free length (EXHAUST): | 30.500 mm (1.2008 in) |
| Camshaft lobe height (INTAKE): | 27.700 mm (1.0905 in) |
| Camshaft lobe height (EXHAUST): | 27.750 mm (1.0925 in) |
Tightening torque
| Tightening torque specs | |
| Connecting rod bolt | 12 Nm; 1.2 kg·m; 9 ft·lb |
| Cylinder head bolt | 24 Nm; 2.4 kg·m; 17 ft·lb |
| Flywheel nut | 75 Nm; 7.5 kg·m; 54 ft·lb |
| Rocker arm pivot lock nut | 10 Nm; 1.0 kg·m; 7 ft·lb |
| Rocker arm pivot bolt | 24 Nm; 2.4 kg·m; 17 ft·lb |
| Crankcase cover bolt | 12 Nm; 1.2 kg·m; 9 ft·lb |
| Oil level switch joint nut | 10 Nm; 1.0 kg·m; 7 ft·lb |
| Oil drain bolt | 18 Nm; 1.8 kg·m; 13 ft·lb |
| Standard torque values | |
| Bolt, nut (5 mm) | 5.5 Nm; 0.55 kg·m; 4.0 ft·lb |
| Bolt, nut (6 mm) | 10 Nm; 1.0 kg·m; 7 ft·lb |
| Bolt, nut (8 mm) | 24 Nm; 2.4 kg·m; 17 ft·lb |
| Bolt, nut (10 mm) | 37.5 Nm; 3.75 kg·m; 27 ft·lb |
| Bolt, nut (12 mm) | 55 Nm; 5.5 kg·m; 40 ft·lb |
Service Data
| Engine | |
| Maximum speed: | 3,900 ± 100 rpm |
| Idle speed: | 1,400 ± 150 rpm |
| Cylinder compression: | 6.0-8.5 kg/cm2 (85-121 psi) at 600 rpm |
| Valve clearance | |
| Intake valve clearance: | 0.15±0.02 mm (0.006±0.001 in) |
| Exhaust valve clearance: | 0.20±0.02 mm (0.008±0.001 in) |
| Oil system | |
| Lubrication system: | Splash |
| Oil type: | Honda 4-stroke or an equivalent (SE or SF) |
| Recommended oil: | SAE 10W-30 |
| Oil capacity: | 0.6 L (0.63 US. qt, 0.53 Imp. qt.) |
| Fuel system | |
| Type: | Horizontal type carburetor with butterfly valve |
| Main jet: | Externally vented carburetor bowl: #60 Internally vented carburetor bowl: #62 |
| Float height: | 13.7 mm (0.5394 in) |
| Pilot screw opening: | Externally vented carburetor bowl: 2 turns out Internally vented carburetor bowl: 2-3/8 turns out turns out |
| Ignition system | |
| Type: | Transistorized magneto ignition |
| Ignition timing: | 25° B.T.D.C. (Fixed) |
| Spark plug: | NGK BP6ES, BPR6ES NIPPONDENSO W20EP-U, W20EPR-U |
| Spark plug gap: | 0.7-0.8 mm (0.0276-0.0315 in) |
| Ignition coil air gap | 0.2-0.6 mm (0.0079-0.0236 in) |
Applications
| Manufacturer or Brand | Models |
| Generators | |
| Honda | EG1200X, EG1400X |
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