Kubota Z402-EB

The 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 code	Z402-EB
Layout	Straight-2, vertical diesel engine
Fuel type	Diesel fuel No.2-D
Production	–
Displacement	0.4 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 type	Indirect injection
Fuel system	Bosch MD type mini pump
Cooling system	Water with pressurized radiator
Starting system	Electric starting with 12V (1.2 kW) starter
Starting support device	Glow plug in combustion chamber
Governor	Centrifugal ball mechanical governor
Power adder	None
Firing order	1-2
Dimensions (L x W x H):	314.5 x 380.4 x 449.1 mm (12.38 x 14.98 x 17.68 in)
Weight	56 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:	Second	0.085-0.112 mm (0.0033 to 0.0044 in)
	Oil	0.040-0.080 mm (0.0016 to 0.0031 in)
Piston ring end gap:	Top	0.250-0.400 mm (0.0098-0.0157 in)
	Second	0.250-0.400 mm (0.0098-0.0157 in)
	Oil	0.150-0.300 mm (0.0059-0.0117 in)
Piston pin outer diameter		20.002-20.011 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	–
	EXHAUST	–
Valve stem diameter:	INTAKE	5.968-5.980 mm (0.2349 to 0.2354 in)
	EXHAUST	5.968-5.980 mm (0.2349 to 0.2354 in)
Valve seat angle:	INTAKE	45°
	EXHAUST	45°

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 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	2.84-3.23 MPa (29.0-33.0 kgf/cm2, 412-469 psi)
Oil system
Recommended engine oil	CD or CE
SAE Viscosity Number	SAE 10W-30, 10W-40
Engine oil capacity	1.9 liters (2.0 US.qts, 1.67 Imp. qts)
Oil filter type	Full-flow paper filter (cartridge type)
Cooling system
Type	Water with pressurized radiator
Coolant capacity	–
Electrical system
Battery:	12V, CCA 600A or equivalent