Kubota D850-B

Kubota D850-BThe Kubota D850-B is a 855 cc (52.2 cu-in) straight-three, water-cooled naturally aspirated diesel engine from Kubota 70 mm series.

The Kubota D850-B engine has a spherical type сombustion сhamber with glow plug, Bosch K-type mini fuel injection pump, and Bosch throttle type injection nozzle. The compression ratio rating is 22.0:1. The cylinder bore and the piston stroke are 72.0 mm (2.83 in) and 70.0 mm (2.76 in), respectively.

The D850-B diesel engine produced 20.3 PS (14.9 kW; 20.0 HP) at 3,000 rpm of gross (intermittent) horsepower and 50.6 N·m (5.2 kg·m, 37.3 ft·lb) at 1,800 rpm of torque.

The breakdown of the engine code is as follows:

  • D – 3-cylinders
  • 85 – Approximate displacement 850 cc

General information

Engine Specifications
Engine codeD850-B
LayoutStraight-3, vertical diesel engine
Fuel typeDiesel fuel No.2-D
Displacement855 cm3 (52.2 cu in)
Max. Horsepower Net (continuous): 15.8 PS (11.6 KW; 15.5 HP) at 3,000 rpm
Net (intermittent): 18.2 PS (13.4 kW; 18.0 HP) at 3,000 rpm
Gross (intermittent): 20.3 PS (14.9 kW; 20.0 HP) at 3,000 rpm
Torque output50.6 N·m (5.2 kg·m, 37.3 ft·lb) at 1,800 rpm
Injection typeIndirect injection
Cooling systemLiquid-cooled
Fuel injection pumpBosch K-type type mini fuel injection pump
Fuel nozzleBosch throttle type
Starting systemElectric starting with 12V (0.8 kW) starter
Starting support deviceGlow plug in combustion chamber
GovernorCentrifugal ball mechanical governor
Power adderNone
Firing order1-2-3
Dimensions (L x W x H):471 x 423 x 566 mm (18.5 x 16.7 x 22.3 in)
Weight82.6 kg (182.1 lbs)

Cylinder block

Cylinder block
Compression ratio:22.0:1
Cylinder bore:72.0 mm (2.83 in)
Piston stroke:70.0 mm (2.76 in)
Number of piston rings (compression / oil):2 / 1
Cylinder inner diameter:72.000-72.019 mm (2.8346-2.8354 in)
Piston skirt diameter
Piston ring side clearance:Second0.085-0.112 mm (0.0033-0.0044 in)
Oil0.020-0.055 mm (0.0008-0.0022 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)
Oil0.250-0.400 mm (0.0098-0.0157 in)
Piston pin outer diameter20.002-20.011 mm (0.7875-0.7878 in)
Crankshaft main journal diameter:43.934-43.950 mm (1.7297-1.7303 in)
Crankpin diameter:36.959-36.975 mm (1.4551-1.4557 in)

Cylinder head

Cylinder head
Valves:6 (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 seat width:INTAKE2.120 mm (0.0835 in)
EXHAUST2.120 mm (0.0835 in)
Valve stem diameter:INTAKE6.960-6.975 mm (0.274-0.2746 in)
EXHAUST6.960-6.975 mm (0.274-0.2746 in)
Valve spring free length:INTAKE35.100-34.800 mm (1.3819-1.3701 in)
EXHAUST35.100-34.800 mm (1.3819-1.3701 in)
Camshaft lobe height:INTAKE26.880 mm (1.0583 in)
EXHAUST26.880 mm (1.0583 in)
Camshaft journal diameter:32.934-32.950 mm (1.2966-1.2972 in)

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
Standard3.09 MPa, 31.5 kgf/cm2, 448 psi
Oil system
Recommended engine oilCC or higher
SAE Viscosity NumberSAE 10W-30, 10W-40
Engine oil capacity4.6 L (4.86 US. qt, 4.05 Imp. qt.)
Cooling system
TypeWater with pressurized radiator
Coolant capacity4.6 L (4.9 US. qt, 4.0 Imp. qt.)
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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