Honda GX120 T1

Honda GX120 T1The 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:

  • 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: 0.13-0.17 mm (0.0051-0.0067 in)
Exhaust valve clearance: 0.18-0.22 mm (0.0071-0.0087 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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