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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We try to use official documentation and verify the published data, but errors may occur. In addition, specifications of machinery and equipment may vary depending on markets and modifications. We do not recommend the use of this data for spare parts or repairs. Use official service manuals or parts catalogs for your product.

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