The 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
Production
–
Displacement
0.64 L, 638 cm3 (38.9 cu in)
Max. Horsepower
16.0 PS (11.8 KW; 15.8 HP) at 3,200 rpm
Torque output
–
Injection type
Indirect injection
Cooling system
Liquid-cooled
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
Firing order
1-2-3
Dimensions (L x W x H):
–
Weight
–
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
–
Oil
–
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)
Oil
–
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:
6 (2 valves per cylinder)
Valve timing:
INTAKE
–
EXHAUST
–
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°
EXHAUST
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
Author:Sergei WersAbout: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.
The Kubota D640 is a 638 cc (38.9 cu·in) straight-tree, water-cooled naturally aspirated diesel engine manufactured by Kubota. 
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