Kubota Z402-EB

Kubota Z402-EBThe Kubota Z402-EB is a 400 cc, (24.41 cu·in) natural aspirated two-cylinders four-stroke liquid-cooled internal combustion small diesel engine, manufactured by Kubota for general-purpose applications.

The cylinder bore is 64.0 mm (2.52 in) and the piston stroke is 62.2 mm (2.45 in). The compression ratio rating is 23.0:1.

This engine produced 8.6 PS (6.3 KW; 8.4 HP) at 3,000 rpm of net (intermittent) power and 8.8 PS (6.5 KW; 8.7 HP) at 3,000 rpm of gross (intermittent) power.

The Kubota Z402-EB features:

  • Spherical type combustion chamber
  • Bosch MD type mini pump
  • Centrifugal ball mechanical governor
  • Forced lubrication by trochoid pump
  • Water cooling system with pressurized radiator
  • Electric starter (12V, 1.2 kW)

General information

Engine Specifications
Engine modelZ402-EB
Engine type4-stroke, OHV, two-cylinders
Displacement400 cm3, (24.41 cu·in)
Max. horsepower Net (intermittent): 8.6 PS (6.3 KW; 8.4 HP) at 3,000 rpm
Gross (intermittent): 8.8 PS (6.5 KW; 8.7 HP) at 3,000 rpm
Gross (cont.): 7.5 PS (5.5 KW; 7.4 HP) at 3,000 rpm
Max. torque
Cooling systemLiquid-cooled with pressurized radiator
Lubricating systemForced lubrication by pump
Fuel systemBosch MD type mini pump
Injection typeIndirect injection
Fuel usedDiesel fuel No.2-D
Starting systemElectric starter (12V, 1.2 kW)
GovernorCentrifugal ball mechanical governor
PTO shaft rotationCounterclockwise (from PTO shaft side)
Dimensions (L x W x H):314 x 380 x 449 mm (12.38 x 14.98 x 17.68 in)
Weight:56 kg (123.5 Ibs)

Cylinder Block and Head

Cylinder block
Compression ratio:23.0:1
Cylinder bore:64.0 mm (2.52 in)
Piston stroke:62.2 mm (2.45 in)
Cylinder internal diameter (standard):64.000-64.019 mm (2.5199-2.5204 in)
Piston skirt outer diameter (standard):
Number of piston rings (compression / oil):2/1
Piston ring side clearance (Second):0.085-0.112 mm (0.0033 to 0.0044 in)
Piston ring side clearance (Oil):0.040-0.080 mm (0.0016 to 0.0031 in)
Ring end gap (Top):0.250-0.400 mm (0.0098-0.0157 in)
Ring end gap (Second):0.250-0.400 mm (0.0098-0.0157 in)
Ring end gap (Oil):0.150-0.300 mm (0.0059-0.0117 in)
Crankshaft main journal diameter: Bearing №1,3: 39.934-39.950 mm (1.5722-1.5728 in)
Bearing №2: 43.934-43.950 mm (1.7297-1.7303 in)
Crankpin journal diameter:33.959-33.975 mm (1.337-1.3376 in)
Cylinder head
Valve arrangement:OHV, gear driven
Valves:4 (2 valves in total)
Valve timing (INTAKE): Open: 20° Before T.D.C.
Close: 45° After B.D.C.
Valve timing (EXHAUST): Open: 50° Before B.D.C.
Close: 15° After T.D.C.
Valve steam diameter (INTAKE):5.968-5.980 mm (0.2349 to 0.2354 in)
Valve steam diameter (EXHAUST):5.968-5.980 mm (0.2349 to 0.2354 in)
Valve seat angle (INTAKE):45°
Valve seat angle (EXHAUST):45°
Valve face angle (INTAKE):45°
Valve face angle (EXHAUST):45°
Valve spring free length (INTAKE):31.6 mm (1.244 in)
Valve spring free length (EXHAUST):31.6 mm (1.244 in)
Rocker arm shaft outer diameter (standard):10.473-10.484 mm (0.41232-0.41276 in)
Rocker arm inner diameter (standard):10.500-10.518 mm (0.4134-0.4141 in)

Tightening torque

Tightening torque specs
Cylinder head screws (M8x1.25):37.2-42.1 Nm (3.8-4.3 kgf-m, 27.5-31.1 lb-ft)
Main bearing case screws 1 (M6x1.0):12.7-15.7 Nm (1.3-1.6 kgf-m, 9.4-11.6 lb-ft)
Main bearing case screws 1
(Flywheel side) (M8x1.25):
23.5-27.4 Nm (2.4-2.8 kgf-m, 17.4-20.3 lb-ft)
Main bearing case screws 2 (M7x1.0):26.5-30.4 Nm (2.7-3.1 kgf-m, 19.5-22.4 lb-ft)
Connecting rod screws (M7x0.75):26.5-30.4 Nm (2.7-3.1 kgf-m, 19.5-22.4 lb-ft)
Flywheel screws (M10x1.25):53.9-58.8 Nm (5.5-6.0 kgf-m, 39.8-43.4 lb-ft)
Rocker arm bracket nuts (M6x1.0):9.8-11.5 Nm (1.0-1.15 kgf-m, 7.2-8.3 lb-ft)
Bearing case cover screws (M6x1.0):9.8-11.5 Nm (1.0-1.15 kgf-m, 7.2-8.3 lb-ft)
Idle gear shaft screws (M6x1.0):9.8-11.5 Nm (1.0-1.15 kgf-m, 7.2-8.3 lb-ft)
Crankshaft end bolt (M12x1.5):117.6-127.4 Nm (12.0-13.0 kgf-m, 86.4-93.6 lb-ft)
Glow plugs (M8x1.0):7.8-14.7 Nm (0.8-1.5 kgf-m, 5.8-10.8 lb-ft)

Service Data

Valve clearance
Intake valve clearance:0.145-0.185 mm (0.0057-0.0073 in)
Exhaust valve clearance:0.145-0.185 mm (0.0057-0.0073 in)
Oil system
Lubrication system:Forced lubrication by pump
Oil type:API CD or CE
Recommended oil:SAE 30, 10W-30
Oil capacity:1.9 liters (2.0 US.qts, 1.67 Imp. qts)
Oil filter type:Full flow paper filter (cartridge)
Oil pressure indicating:Electrical type switch
Oil pressure: At Idle speed: 98 kPa (1.O kgf/cm2, 14 psi)
At Rated speed: 196.0-441.O kPa (2.0-4.5 kgf/cm2, 28.0-64.0 psi)
Cooling system
TypeLiquid-cooled with pressurized radiator
Coolant capacity
Thermostat’s valve opening temperature69.5-72.5 °C (157.1-162.5 °F)
Temperature at which thermostat completely opens85 °C (185 °F)
Fuel system
Type:Bosch MD type mini pump
Injection timing:18-20° Before T.D.C.
Injection nozzle fuel injection pressure:13.73-14.71 MPa (140-150 kgf/cm2, 1991-2133 psi)
Electrical system
Battery:12V, CCA 600A or equivalent
Starting motorElectric starter (12V, 1.2 kW)
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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