Kubota D722

Kubota D722The Kubota D722 is a 0.7 L (719 cc, 43.9 cu·in) straight-three, water-cooled naturally aspirated diesel engine manufactured by Kubota.

The Kubota D722 engine has a spherical type сombustion сhamber with glow plug, Bosch MD mini fuel injection pump, and Bosch throttle type injection nozzle. The compression ratio rating is 23.0:1 or 23.5:1. Cylinder bore is 67.0 mm (2.64 in) and piston stroke is 68.0 mm (2.68 in). The D722 diesel engine produced 21.2 PS (15.6 kW; 20.9 HP) at 3,600 rpm of gross (intermittent) horsepower and 45.8 Nm (4.67 kg·m; 33.8 ft·lb) at 2,600 rpm of torque.

The breakdown of the engine code is as follows:

  • D – 3-cylinders
  • 72 – Approximate displacement 720 cc

General information

Engine Specifications
Engine code D722-B(E), -E, -E2B, -E3B
Layout Straight-3, vertical diesel engine
Fuel type Diesel fuel No.2-D
Displacement 0.7 L, 719 cm3 (43.9 cu in)
Fuel injection pump Bosch MD type mini fuel injection pump
Fuel nozzle Bosch throttle type
Starting system Electric starting with 12V (0.8 kW) starter
Starting support device Glow plug in combustion chamber
Governor Centrifugal ball mechanical governor
Power adder None
Max. Horsepower 21.2 PS (15.6 kW; 20.9 HP) at 3,600 rpm
Torque output 45.8 Nm (4.67 kg·m; 33.8 ft·lb) at 2,600 rpm
Firing order 1-2-3
Dimensions (L x W x H): 426 x 398 x 519 mm (16.8 x 15.7 x 20.4 in)
Weight 63.7 kg (140.4 lbs)

Cylinder block

Cylinder block
Compression ratio: 23.0:1 for D722-B(E)
23.5:1 for D722-E2B, D722-E3B, D722-E
Cylinder bore: 67.0 mm (2.64 in)
Piston stroke: 68.0 mm (2.68 in)
Number of piston rings (compression / oil): 2 / 1
Cylinder inner diameter: 67.000-67.019 mm (2.6378-2.6385 in)
Piston skirt diameter
Piston ring side clearance: Second 0.085-0.112 mm (0.0033-0.0044 in)
Oil 0.020-0.060 mm (0.0008-0.0024 in)
Piston ring end gap: Top 0.150-0.300 mm (0.0059-0.0118 in)
Second 0.300-0.450 mm (0.0118-0.0177 in)
Oil 0.150-0.300 mm (0.0059-0.0118 in)
Piston pin outer diameter 20.002-20.011 mm (0.7875-0.7878 in)
Crankshaft main journal diameter: Flywheel side: 43.934-43.950 mm (1.72969-1.73032 in)
Other: 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 Open: 20° B.T.D.C.
Close: 45° B.T.D.C.
EXHAUST Open: 50° B.T.D.C.
Close: 15° B.T.D.C.
Valve seat width: INTAKE 2.120 mm (0.0835 in)
EXHAUST 2.120 mm (0.0835 in)
Valve stem diameter: INTAKE 5.968-5.980 mm (0.2349-0.2354 in)
EXHAUST 5.968-5.980 mm (0.2349-0.2354 in)
Valve spring free length: INTAKE 31.6 mm (1.2441 in)
EXHAUST 31.6 mm (1.2441 in)
Camshaft lobe height: INTAKE 26.88 mm (1.0583 in)
EXHAUST 26.88 mm (1.0583 in)
Camshaft journal diameter: 32.934-32.950 mm (1.2966-1.2972 in)

Tightening torque

Tightening torque specs
Head cover cap nuts (M6x1.0): 3.9-5.3 Nm (0.4-0.6 kgf-m, 2.9-4.3 lb-ft)
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)
Flywheel bolts (M10x1.25): 53.9-58.8 Nm (5.5-6.0 kgf-m, 39.8-43.4 lb-ft)
Connecting rod bolts (M7x0.75): 26.5-30.4 Nm (2.7-3.1 kgf-m, 19.5-22.4 lb-ft)
Rocker arm bracket nuts (M6x1.0): 9.81-11.28 Nm (1.0-1.15 kgf-m, 7.23-8.32 lb-ft)
Idle gear shaft bolts (M6x1.0): 9.8-11.3 Nm (1.00-1.15 kgf-m, 7.2-8.3 lb-ft)
Idle gear shaft screws (M6x1.0): 9.8-11.3 Nm (1.00-1.15 kgf-m, 7.2-8.3 lb-ft)
Glow plugs (M8x1.0): 7.8-14.7 Nm (0.8-1.5 kgf-m, 5.8-10.8 lb-ft)
Nozzle holder assembly (M20x1.5): 49.0-68.6 Nm (5.0-7.0 kgf-m, 36.2-50.6 lb-ft)
Nozzle holder and nozzle retaining nut: 58.8-78.5 Nm (6.0-8.0 kgf-m, 43.4-57.9 lb-ft)
Injection pipe retaining nuts: 24.5-34.3 Nm (2.5-3.5 kgf-m, 18.1-25.3 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 2.84-3.24 MPa, 29-33 kgf/cm2, 412-469 psi
Oil system
Recommended engine oil CD or CE
SAE Viscosity Number SAE 10W-30, 10W-40
Engine oil capacity Oil pan depth 101 mm (3.98 in): 3.2 L (3.38 US. qt, 2.82 Imp. qt.)
Oil pan depth 121 mm (4.76 in): 3.8 L (4.00 US. qt, 3.31 Imp. qt.)
Fuel system
Injection timing: 20-22° B.T.D.C. for D722-B(E)
19-21° B.T.D.C. for D722-E2B
20.25-21.75° B.T.D.C. for D722-E3B
20° B.T.D.C. for D722-E
Fuel injection pressure 13.73-14.71 MPa (140-150 kgf/cm2, 1991-2133 psi)
Cooling system
Coolant capacity 3.1 liters (3.3 US.qts, 2.7 Imp. qts)
Thermostat’s valve opening temperature: 69.5-72.5°C (157.1-162.5°F)
Temperature at which thermostat completely opens: 85°C (185°F)
Electrical system
Battery: 12V, 35Ah or equivalent
Starter mica undercut: 0.5-0.8 mm (0.0197-0.0315 in)
Starter brush length: 16.0 mm (0.6299 in)
Alternator (no-load voltage): AC 20V at 5,200 rpm
Glow plug resistance: Approx 0.9 Ω
Alternator stator resistance: Less than 1.0 Ω
Alternator rotor resistance: Less than 2.9 Ω
Alternator slip ring: 14.4 mm (0.567 in)
Alternator brush Length: 10.5 mm (0.413 in)
Author: Sergei Wers
About: 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.

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