Kubota Z402-EB

Kubota Z402-EBThe Kubota Z402-EB is a 400 cc (24.41 cu·in) straight-two, water-cooled naturally aspirated diesel engine manufactured by Kubota.

The Kubota Z402-EB engine has a spherical type сombustion сhamber with a glow plug. 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.

The Z402-EB diesel 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 breakdown of the engine code is as follows:

  • Z – 2-cylinders
  • 402 – Approximate displacement 400 cc
  • EB – Early industrial diesel

General information

Engine Specifications
Engine codeZ402-EB
LayoutStraight-2, vertical diesel engine
Fuel typeDiesel fuel No.2-D
Displacement0.4 L, 400 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
Torque output
Injection typeIndirect injection
Fuel systemBosch MD type mini pump
Cooling systemWater with pressurized radiator
Starting systemElectric starting with 12V (1.2 kW) starter
Starting support deviceGlow plug in combustion chamber
GovernorCentrifugal ball mechanical governor
Power adderNone
Firing order1-2
Dimensions (L x W x H):314.5 x 380.4 x 449.1 mm (12.38 x 14.98 x 17.68 in)
Weight56 kg (123.5 Ibs)

Cylinder block

Cylinder block
Compression ratio:23.0:1
Cylinder bore:64.0 mm (2.52 in)
Piston stroke:62.2 mm (2.45 in)
Number of piston rings (compression / oil):2 / 1
Cylinder inner diameter:64.000-64.019 mm (2.5199-2.5204 in)
Piston skirt diameter
Piston ring side clearance:Second0.085-0.112 mm (0.0033 to 0.0044 in)
Oil0.040-0.080 mm (0.0016 to 0.0031 in)
Piston ring end gap:Top0.250-0.400 mm (0.0098-0.0157 in)
Second0.250-0.400 mm (0.0098-0.0157 in)
Oil0.150-0.300 mm (0.0059-0.0117 in)
Piston pin outer diameter20.002-20.011 mm (0.7875-0.7878 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 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 Open: 20° B.T.D.C.
Close: 45° A.B.D.C.
EXHAUST Open: 50° B.B.D.C.
Close: 15° A.T.D.C.
Valve head diameter:INTAKE
Valve stem diameter:INTAKE5.968-5.980 mm (0.2349 to 0.2354 in)
EXHAUST5.968-5.980 mm (0.2349 to 0.2354 in)
Valve seat angle:INTAKE45°

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 Kubota 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)

Maintenance data

Valve clearance
Intake valve0.145-0.185 mm (0.0057-0.0073 in)
Exhaust valve0.145-0.185 mm (0.0057-0.0073 in)
Compression pressure
Standard2.84-3.23 MPa (29.0-33.0 kgf/cm2, 412-469 psi)
Oil system
Recommended engine oilCD or CE
SAE Viscosity NumberSAE 10W-30, 10W-40
Engine oil capacity1.9 liters (2.0 US.qts, 1.67 Imp. qts)
Oil filter typeFull-flow paper filter (cartridge type)
Cooling system
TypeWater with pressurized radiator
Coolant capacity
Electrical system
Battery:12V, CCA 600A or equivalent
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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