The Honda GXR120 T/RT is a 121 cc, (7.4 cu·in) natural aspirated single-cylinder four-stroke air-cooled internal combustion 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 43.0 mm (1.69 in), respectively. Compression ratio rating is 8.5:1.
The Honda GXR120 T/RT engine produced 3.7 PS (2.7 kW; 3.6 HP) at 3,600 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 GXR120 T/RT features:
- Overhead camshaft (OHC) design
- Transistorized magneto ignition system
- Float type, Horizontal butterfly valve type or Diaphragm type
- Centrifugal governor
- Splash lubrication system
- Forced air cooling system
- Recoil starter
General information
| Engine Specifications | |
| Engine model | GXR120 T/RT |
| Engine type | 4-stroke, OHC, single-cylinder |
| Displacement | 121 cm3, (7.38 cu·in) |
| Max. horsepower | 3.7 PS (2.7 kW; 3.6 HP) at 3,600 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 | GXR120T: Single type, Dual type GXR120RT: Single type, Dual type, Elbow type |
| Lubricating system | Splash |
| Ignition system | Transistorized magneto ignition |
| Fuel system | Float type, Horizontal butterfly valve type or Diaphragm type |
| Fuel consumption | 1.0 L (0.26 US gal, 0.22 Imp gal)/h |
| Fuel tank capacity | – |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Starting system | Recoil starter |
| Stoping system | Ignition primary circuit ground |
| Governor | Mechanical centrifuga |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
Cylinder Block and Head
| Cylinder block | |
| Compression ratio: | 8.5:1 |
| Cylinder bore: | 60.0 mm (2.36 in) |
| Piston stroke: | 43.0 mm (1.69 in) |
| Cylinder internal diameter (standard): | 60.000-60.015 mm (2.3622-2.3628 in) |
| Piston skirt outer diameter (standard): | 59.971-59.985 mm (2.3611-2.3616 in) |
| Number of piston rings (compression / oil): | 2/1 |
| Connecting rod big end diameter (standard): | 26.020-26.033 mm (1.0244-1.0249 in) |
| Connecting rod small end diameter (standard): | 13.005-13.020 mm (0.512-0.5126 in) |
| Piston pin diameter: | 12.994-13.000 mm (0.5116-0.5118 in) |
| Side clearance (Top): | 0.015-0.054 mm (0.0006-0.0021 in) |
| Side clearance (Second): | 0.030-0.069 mm (0.0012-0.0027 in) |
| Ring end gap (Top): | 0.150-0.300 mm (0.0059-0.0118 in) |
| Ring end gap (Second): | 0.400-0.550 mm (0.0157-0.0217 in) |
| Ring end gap (Oil): | 0.200-0.700 mm (0.0079-0.0276 in) |
| Ring width (Top): | 0.970-0.990 mm (0.0382-0.039 in) |
| Ring width (Second): | 1.155-1.175 mm (0.0455-0.0463 in) |
| Crankpin journal diameter: | 25.970-25.980 mm (1.0224-1.0228 in) |
| Crankshaft center distance: | 21.5 mm (0.845 in) |
| Cylinder head | |
| Valve arrangement: | OHC, gear driven |
| 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): | 25.8 mm (1.0157 in) |
| Valve spring free length (EXHAUST): | 25.8 mm (1.0157 in) |
| Camshaft lobe height (INTAKE): | 36.483 mm (1.4363 in) |
| Camshaft lobe height (EXHAUST): | 36.483 mm (1.4363 in) |
Service Data
| Engine | |
| Maximum speed: | 4,100 ± 100 rpm |
| Idle speed: | 1,850 ± 150 rpm |
| Cylinder compression: | 5.1 kg/cm2 (73 psi) at 700 rpm |
| Valve clearance | |
| Intake valve clearance: | 0.15±0.04 mm (0.006±0.002 in) |
| Exhaust valve clearance (COLD): | 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 higher) |
| Recommended oil: | SAE 10W-30 |
| Oil capacity: | 0.28 L (0.3 US. qt, 0.25 Imp. qt.) |
| Fuel system | |
| Type: | Float type, Horizontal butterfly valve type or Diaphragm type |
| Main jet: | Float type BF33S A: #60 BF33R A: #60 Floatless type #48 |
| Float height: | 15.7 mm (0.6181 in) |
| Pilot screw opening: | Float type BF33S A: 3-1/2 turns out BF33R A: 3-3/8 turns out Floatless type 2-3/4 turns out |
| Ignition system | |
| Type: | Transistorized magneto ignition |
| Ignition timing: | 25° B.T.D.C. |
| Spark plug: | NGK: CR5HSB DENSO: U16FSR-UB |
| Spark plug gap: | 0.7-0.8 mm (0.0276-0.0315 in) |
| Ignition coil air gap | 0.5-0.7 mm (0.0197-0.0276 in) |
Applications
| Manufacturer or Brand | Models |
| Generators | |
| Honda | EB2200i |
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