Honda GX120T2

The Honda GX120 T2 is a 118 cc (7.2 cu-in) single-cylinder inclined by 25° air-cooled 4-stroke internal combustion small gasoline engine with horizontal shaft manufactured by Honda Motor Company for general-purpose applications, such as commercial lawn and garden equipment, tillers and cultivators, generators, construction and industrial equipment, agricultural equipment and water pumps.

The Honda GX120 T2 engine has an OHV (overhead valve) design; high compression ratio for better fuel efficiency; horizontal type carburetor with butterfly valve; mechanical centrifugal governor; forced splash lubrication system; heavy-duty recoil starter and C.D.I. (Capacitor Discharge Ignition) type magneto ignition. The engine can be equipped with the dual-type, semi-dry type, dual silent type, oil bath type or cyclone-type air cleaner

The cylinder bore is 60.0 mm (2.4 in) and the piston stroke is 42.0 mm (1.7 in), compression ratio rating is 8.5:1. The engine produced 3.5 HP (2.6 kW) at 3,600 rpm of maximum horsepower and 2.9 HP (2.1 kW) at 3,600 rpm of continuous rated power. Maximum torque is 7.3 N·m (0.7 kg·m, 5.4 ft·lb) at 2,500 rpm.

General information

Engine Specifications
Model GX120 T2 / UT2
Type 4-stroke, OHV, single cylinder inclined by 25°
Displacement 118 cm 3 (7.2 cu-in)
Max. horsepower 3.5 HP (2.6 kW) at 3,600 rpm
Max. torque (crank PTO) 7.3 N·m (0.7 kg·m, 5.4 ft·lb) at 2,500 rpm
Carburetor Horizontal type, butterfly valve
Cooling system Forced-air
Ignition system C.D.I. (Capacitor Discharge Ignition)
Lubricating system Forced splash
Starting system Recoil starter
Stoping system Ignition primary circuit ground
Fuel used Unleaded gasoline (octane number 86 or higher)
Fuel tank capacity 2.0 L (0.53 US Gal, 0.44 Imp Gal.)
PTO shaft rotation Counterclockwise (from PTO shaft side)

Cylinder Block and Head

The Honda GX120T2 has cast iron cylinder sleeve, ball bearing supported forged steel crankshaft, improved piston design. The piston has two compression rings and one oil ring. Precision camshaft design offers precise valve timing and optimal valve overlap for better fuel efficiency. Cylinder bore and piston stroke are 60.0 mm (2.4 in) and 42.0 mm (1.7 in), respectively. Compression ratio rating is 8.5:1

Cylinder block
Compression ratio: 8.5:1
Bore x Stroke 60 X 42 mm (2.4 x 1.7 in)
Sleeve internal diameter 60.00 mm (2.36 in)
Piston skirt outer diameter 59.985 mm (2.3616 in)
Number of piston rings (compression / oil): 2 / 1
Ring side clearance Top 0.035-0.070 mm (0.0014-0.0028 in)
Second 0.045-0.080 mm (0.0018-0.0032 in)
Ring end gap Top 0.20-0.35 mm (0.0079-0.0138 in)
Second 0.35-0.50 mm (0.0138-0.0197 in)
Oil (side rail) 0.2-0.7 mm (0.01-0.03 in)
Ring width Top 0.95-0.97 mm (0.0374-0.0382 in)
Second 0.94-0.96 mm (0.0370-0.0378 in)
Connecting rod small end ID 13.005 mm (0.5120 in)
Connecting rod big end ID 26.02 mm (1.024 in)
Piston pin outer diameter 13.0 mm (0.51 in)
Crankshaft crank pin outer diameter 25.98 mm (1.023 in)
Cylinder Head
Warpage (limit) 0.10 mm (0.004 in)
Valve Arrangement: OHV
Valves: 2
Stem outer diameter (standard): INTAKE 5.468-5.480 mm (0.2153-0.2157 in)
EXHAUST 5.425-5.440 mm (0.2136-0.2142 in)
Valve spring free length: 30.5 mm (1.20 in)
Camshaft outer diameter: 13.984 mm (0.5506 in)
Cam height: INTAKE 27.500-27.900 mm (1.0827-1.0984 in)
EXHAUST 27.547-27.947 mm (1.0845-1.1003 in)

Tightening torque specs

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 adjusting 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

Service Information

Maximum speed 3,900 ± 100 rpm
Idle speed 1,400 ± 150 rpm
Cylinder compression 5.0-7.0 kg/cm2 (71-100 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
Oil type Honda 4-stroke or an equivalent (SJ or higher)
Recommended oil SAE 10W-30
Oil capacity 0.56 L (0.59 US. qt, 0.49 Imp. qt.)
Main jet BE99A: #60
BE60W, BE61M, BE99B: #62
Float height 13.7 mm (0.54 in)
Pilot screw opening BE99A: 2 turns out
BE60W, BE61M, BE99B: 2-3/8 turns out
Ignition system
Ignition timing 20° B.T.D.C.
Spark plug NGK: BPR6ES
Spark plug gap 0.7-0.8 mm (0.028-0.031 in)
Primary ignition coil resistance 0.6-0.9 Ω
Secondary ignition coil resistance 5.6-6.9 kΩ
Ignition coil air gap 0.4 ± 0.2 (0.016 ± 0.008)
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