Kubota Z400 (399 cc) diesel engine: specs and review, service data

The Kubota Z400 is a 399 cc (24.3 cu·in) straight-two, water-cooled naturally aspirated diesel engine manufactured by Kubota.

The Kubota Z400 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 Z400 diesel engine produced 10.2 PS (7.5 kW; 10.0 HP) at 3,200 rpm of horsepower.

The breakdown of the engine code is as follows:

Z – 2-cylinders
400 – Approximate displacement 400 cc

General information

Engine Specifications
Engine code	Z400
Layout	Straight-2, vertical diesel engine
Fuel type	Diesel fuel No.2-D
Production	–
Displacement	0.4 L, 399 cm³ (24.3 cu in)
Fuel system	Fuel injection pump
Cooling system	Water with pressurized radiator
Starting system	Electric starting with 12V (0.7 kW) starter
Starting support device	Glow plug in combustion chamber
Governor	Centrifugal ball mechanical governor
Power adder	None
Max. Horsepower	10.2 PS (7.5 kW; 10.1 HP) at 3,200 rpm
Torque output	–
Firing order	1-2
Dimensions (L x W x H):	–
Weight	–

Cylinder block

Cylinder block
Compression ratio:		–
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:		63.989-64.139 mm (2.5192-2.5252 in)
Piston skirt diameter		63.906 mm (2.516 in)
Piston ring side clearance:	Second	–
	Oil	–
Piston ring end gap:	Top	0.430-0.885 mm (0.0169-0.0348 in)
	Second	0.430-0.885 mm (0.0169-0.0348 in)
	Oil	–
Piston pin outer diameter		–
Crankshaft main journal diameter:		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:		4 (2 valves per cylinder)
Valve timing:	INTAKE	–
Valve timing:	EXHAUST	–
Valve head diameter:	INTAKE	26.00 mm (1.0236 in)
Valve head diameter:	EXHAUST	22.50 mm (0.8858 in)
Valve stem diameter:	INTAKE	5.980 mm (0.2354 in)
Valve stem diameter:	EXHAUST	5.980 mm (0.2354 in)
Valve seat angle:	INTAKE	45°
Valve seat angle:	EXHAUST	45°

Tightening torque

Tightening torque specs
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)
Connecting rod bolts (M7x1.0):	26.0 Nm (2.6 kgf-m, 19.0 lb-ft)
Flywheel bolts (M10x1.25):	59.0 Nm (6.0 kgf-m, 44.0 lb-ft)
Rocker arm bracket bolts (M6x1.0):	11.5 Nm (1.15 kgf-m, 8.3 lb-ft)
Fan drive pulley bolt (M12x1.5):	117.0 Nm (17.0 kgf-m, 86.0 lb-ft)
Oil pump mounting bolt (M8x1.25):	20.0 Nm (2.0 kgf-m, 15.0 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	2.24-3.10 MPa, 23-31 kgf/cm², 325-450 psi
Oil system
Recommended engine oil	CD or CE
SAE Viscosity Number	SAE 10W-30, 10W-40
Engine oil capacity	2.0 liters (2.11 US.qts, 1.76 Imp. qts)
Oil filter type	Full-flow paper filter (cartridge)
Cooling system
Type	Water with pressurized radiator
Coolant capacity	1.9 liters (2.0 US.qts, 1.67 Imp. qts)
Electrical system
Battery:	12V, 35Ah 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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