Kubota D640

Kubota D640The Kubota D640 is a 638 cc (38.9 cu·in) straight-tree, water-cooled naturally aspirated diesel engine manufactured by Kubota.

The Kubota D640 engine has a spherical type сombustion сhamber with a glow plug. The cylinder bore is 66.0 mm (2.60 in) and the piston stroke is 62.2 mm (2.45 in).

The Kubota D640 diesel engine produced 16.0 PS (11.8 KW; 15.8 HP) at 3,200 rpm of maximum horsepower.

The breakdown of the engine code is as follows:

  • D – 3-cylinders
  • 640 – Approximate displacement 640 cc

General information

Engine Specifications
Engine code D640
Layout Straight-3, vertical diesel engine
Fuel type Diesel fuel No.2-D
Displacement 0.64 L, 638 cm3 (38.9 cu in)
Fuel system Fuel injection pump
Cooling system Water with pressurized radiator
Starting system Electric starting with 12V (0.7 kW) starter
Starting support device Glow plug in combustion chamber
Governor Centrifugal ball mechanical governor
Power adder None
Max. Horsepower 16.0 PS (11.8 KW; 15.8 HP) at 3,200 rpm
Torque output
Firing order 1-2-3
Dimensions (L x W x H):

Cylinder block

Cylinder block
Compression ratio:
Cylinder bore: 66.0 mm (2.60 in)
Piston stroke: 62.2 mm (2.45 in)
Number of piston rings (compression / oil): 2 / 1
Cylinder inner diameter: 66.130-65.960 mm (2.6044-2.5984 in)
Piston skirt diameter 65.906 mm (2.5957 in)
Piston ring side clearance: Second
Piston ring end gap: Top 0.430-0.885 mm (0.0169-0.0348 in)
Second 0.430-0.885 mm (0.0169-0.0348 in)
Piston pin outer diameter
Crankshaft main journal diameter: 39.934-39.950 mm (1.5722-1.5728 in)
Crankpin diameter: 33.959-33.975 mm (1.337-1.3376 in)

Cylinder head

Cylinder head
Valve Arrangement: OHV, gear drive
Valves: 4 (2 valves per cylinder)
Valve timing: INTAKE
Valve head diameter: INTAKE 26.00 mm (1.0236 in)
EXHAUST 22.50 mm (0.8858 in)
Valve stem diameter: INTAKE 5.980 mm (0.2354 in)
EXHAUST 5.980 mm (0.2354 in)
Valve seat angle: INTAKE 45°

Tightening torque

Tightening torque specs
Head bolts (M8x1.25): 39.2-44.1 Nm (4.0-4.5 kgf-m, 28.9-32.5 lb-ft)
Main bearing case bolts 1 (M6x1.0): 12.7-15.7 Nm (1.3-1.6 kgf-m, 9.4-11.6 lb-ft)
Main bearing case screw 2 (M7x1.0): 26.5-30.4 Nm (2.7-3.1 kgf-m, 19.5-22.4 lb-ft)
Connecting rod bolts (M7x1.0): 26.0 Nm (2.6 kgf-m, 19.0 lb-ft)
Flywheel bolts (M10x1.25): 59.0 Nm (6.0 kgf-m, 44.0 lb-ft)
Rocker arm bracket bolts (M6x1.0): 11.5 Nm (1.15 kgf-m, 8.3 lb-ft)
Fan drive pulley bolt (M12x1.5): 117.0 Nm (17.0 kgf-m, 86.0 lb-ft)
Oil pump mounting bolt (M8x1.25): 20.0 Nm (2.0 kgf-m, 15.0 lb-ft)

Maintenance data

Valve clearance
Intake valve 0.145-0.185 mm (0.0057-0.0073 in)
Exhaust valve 0.145-0.185 mm (0.0057-0.0073 in)
Compression pressure
Standard 2.24-3.10 MPa, 23-31 kgf/cm2, 325-450 psi
Oil system
Recommended engine oil CD or CE
SAE Viscosity Number SAE 10W-30, 10W-40
Engine oil capacity 3.0 liters (3.17 US.qts, 2.64 Imp. qts)
Oil filter type Full-flow paper filter (cartridge)
Cooling system
Type Water with pressurized radiator
Coolant capacity 2.1 liters (2.22 US.qts, 1.85 Imp. qts)
Electrical system
Battery: 12V, 35Ah or equivalent
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