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
| Engine | |
| 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.) |
| Carburetor | |
| 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 DENSO: W20EPR-U |
| 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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