Honda GX630

Honda GX630The 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:

  • OHV design
  • C.D.I. (Capacitor Discharge Ignition) type magneto ignition system
  • 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, two-cylinders
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: 0.06-0.10 mm (0.0024-0.0039 in)
Exhaust valve clearance: 0.08-0.12 mm (0.0031-0.0047 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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