The Honda GX630 is a 688 cc, (42.0 cu·in) natural aspirated V-twin 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 78.0 mm (3.07 in) and 72.0 mm (2.83 in), respectively. The compression ratio rating is 9.3:1.
The Honda GX630 engine produced 21.1 PS (15.5 kW; 20.8 HP) at 3,600 rpm of maximum output power, or 16.3 PS (12.0 kW; 16.1 HP) at 3,600 rpm of continuous rated power and 48.3 N·m (4.9 kg·m, 35.6 ft·lb) at 2,500 rpm of peak torque.
The Honda GX630 features:
- Overhead valve (OHV) design
- C.D.I. (Capacitor Discharge Ignition)
- Two barrel horizontal type carburetor with butterfly valve
- Centrifugal governor
- Forced feed lubrication system
- Forced air cooling system
- Starter motor
General information
| Engine Specifications | |
| Engine model | GX630 |
| Engine type | 4-stroke, OHV, V-twin |
| Displacement | 688 cm3, (41.98 cu·in) |
| Max. horsepower | 21.1 PS (15.5 kW; 20.8 HP) at 3,600 rpm |
| Max. torque | 48.3 N·m (4.9 kg·m, 35.6 ft·lb) at 2,500 rpm |
| Cooling system | Forced air |
| Air cleaner | Dual type |
| Lubricating system | Forced feed |
| Ignition system | C.D.I. (Capacitor Discharge Ignition) type magneto |
| Fuel system | 2 barrel horizontal type carburetor with butterfly valve |
| Fuel consumption | 6.0 Liters (1.59 US gal, 1.32 Imp gal) / h |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Starting system | Starter motor |
| Stoping system | Ignition primary circuit open |
| Governor | Centrifugal governor |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
| Dimensions (L x W X H) | 405 x 410 x 438 mm (15.9 x 16.1 x 17.2 in) |
| Dry weight | 44.0 kg (97 lbs) |
Cylinder Block and Head
| Cylinder block | |
| Compression ratio: | 9.3:1 |
| Cylinder bore: | 78.0 mm (3.07 in) |
| Piston stroke: | 72.0 mm (2.83 in) |
| Cylinder internal diameter (standard): | 78.000-78.015 mm (3.0709-3.0715 in) |
| Piston skirt outer diameter (standard): | 77.985-77.995 mm (3.0703-3.0707 in) |
| Number of piston rings (compression / oil): | 2/1 |
| Connecting rod big end diameter (standard): | 44.988-45.012 mm (1.7712-1.7721 in) |
| Connecting rod small end diameter (standard): | 18.006-18.018 mm (0.7089-0.7094 in) |
| Piston pin diameter: | 17.994-18.000 mm (0.7084-0.7087 in) |
| Side clearance (Top): | 0.050-0.080 mm (0.002-0.0031 in) |
| Side clearance (Second): | 0.050-0.080 mm (0.002-0.0031 in) |
| Ring end gap (Top): | 0.200-0.350 mm (0.0079-0.0138 in) |
| Ring end gap (Second): | 0.200-0.350 mm (0.0079-0.0138 in) |
| Ring end gap (Oil): | 0.200-0.700 mm (0.0079-0.0276 in) |
| Ring width (Top): | 1.140-1.155 mm (0.0449-0.0455 in) |
| Ring width (Second): | 1.140-1.155 mm (0.0449-0.0455 in) |
| Crankshaft main journal diameter: | 39.984-40.000 mm (1.5742-1.5748 in) |
| Crankpin journal diameter: | 44.973-44.983 mm (1.7706-1.771 in) |
| Crankshaft center distance: | 36 mm (1.415 in) |
| Cylinder head | |
| Valve arrangement: | OHV, gear driven |
| Valves: | 2,(4 valves in total) |
| Valve steam diameter (INTAKE): | 5.475-5.490 mm (0.2156-0.2161 in) |
| Valve steam diameter (EXHAUST): | 5.435-5.450 mm (0.214-0.2146 in) |
| Valve spring free length (INTAKE): | 38.3 mm (1.5079 in) |
| Valve spring free length (EXHAUST): | 38.3 mm (1.5079 in) |
| Camshaft lobe height (INTAKE): | 29.506-29.706 mm (1.1617-1.1695 in) |
| Camshaft lobe height (EXHAUST): | 29.410-29.610 mm (1.1579-1.1657 in) |
| Camshaft journal diameter : | 16.982-17.000 mm (0.6686-0.6693 in) |
Tightening torque
| Tightening torque specs | |
| Connecting rod bolt | 22 Nm; 2.2 kg·m; 16 ft·lb |
| Cylinder nut | 37 Nm; 3.8 kg·m; 27 ft·lb |
| Oil drain plug bolt | 45 Nm; 4.5 kg·m; 33 ft·lb |
| Flywheel nut | 235 Nm; 24.0 kg·m; 173 ft·lb |
| Oil filter cartridge | 12 Nm; 1.2 kg·m; 9 ft·lb |
| Tappet adjusting nut | 7.5 Nm; 0.75 kg·m; 5.5 ft·lb |
| Governor arm nut | 11 Nm; 1.1 kg·m; 8 ft·lb |
| Fuel pump cover screw | 4 Nm; 0.4 kg·m; 3 ft·lb |
| Oil pressure switch | 9 Nm; 0.9 kg·m; 6.6 ft·lb |
Service Data
| Engine | |
| Maximum speed: | GX630: 3,600-4,000 rpm GX630R (QYD, VEP4, VXF): 3,000-3,300 rpm GX630R (VXD8, VXE1): 3,050-3,350 rpm |
| Cylinder compression: | 0.5-0.7 MPa (5.09-7.14 kgf/cm2, 73-102 psi) / 500 rpm |
| Valve clearance | |
| Intake valve clearance: | 0.08±0.02 mm (0.003±0.001 in) |
| Exhaust valve clearance: | 0.10±0.02 mm (0.004±0.001 in) |
| Oil system | |
| Lubrication system: | Forced feed |
| Oil type: | API SE or later |
| Recommended oil: | SAE 10W-30 |
| Oil capacity: | Without oil filter replacement: 1.5 L (1.59 US. qt, 1.32 Imp. qt.) With oil filter replacement: 1.7 L (1.80 US. qt, 1.50 Imp. qt.) |
| Fuel system | |
| Type: | 2 barrel horizontal type carburetor with butterfly valve |
| Main jet: | No.1 cylinder: #102 No.2 cylinder: #105 |
| Float height: | 15.5 mm (0.6102 in) |
| Pilot screw opening: | No.1 cylinder: 2 turns out No.2 cylinder: 1-7/8 turns out |
| Ignition system | |
| Type: | C.D.I. (Capacitor Discharge Ignition) type magneto |
| Ignition timing: | B.T.D.C. 9° |
| Spark plug: | NGK: ZFR5F |
| 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) |
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