Kubota D650-A

Kubota D650-AThe KubotaD650-A/AH is a 675 cc, (41.2 cu·in) natural aspirated three-cylinders four-stroke liquid-cooled internal combustion vertical diesel engine, manufactured by Kubota for general-purpose applications.

It has an 64.0 mm (2.52 in) cylinder bore and 70.0 mm (2.76 in) piston stroke. The compression ratio rating is 22.0:1.

The D650-A engine produced 14.1 PS (10.4 KW; 14.0 HP) at 2,800 rpm of gross output power.

The Kubota D650-A features:

  • Spherical type combustion chamber
  • Bosch K-type mini fuel injection pump
  • Bosch throttle type injection nozzle
  • Centrifugal ball mechanical governor
  • Forced lubrication by pump lubrication system
  • Liquid cooling system
  • Electric starter (12V)

General information

Engine Specifications
Engine modelD650-A/D650-AH
Engine type4-stroke, vertical, three-cylinders
Displacement675 cm3, (41.2 cu·in)
Max. horsepower (gross)14.1 PS (10.4 KW; 14.0 HP) at 2,800 rpm
Max. torque
Cooling systemLiquid-cooled
Lubricating systemForced lubrication by pump
Combustion chamberSpherical type
Fuel injection pumpBosch K Type Mini Pump
Injection typeIndirect injection
Injection nozzleBosch throttle type
Firing order1-2-3
Fuel usedDiesel fuel No.2-D
Starting systemElectric starter (12V)
Starting support deviceGlow plug in combustion chamber
GovernorCentrifugal ball mechanical governor
PTO shaft rotationCounterclockwise (from PTO shaft side)
Dimensions (L x W X H)471 x 423 x 566 mm (18.5 x 16.7 x 22.3 in)
Dry weight82.6 kg (182.1 lbs)

Cylinder Block and Head

Cylinder block
Compression ratio:22.0:1
Cylinder bore:64.0 mm (2.52 in)
Piston stroke:70.0 mm (2.76 in)
Cylinder internal diameter (standard):64.000-64.019 mm (2.5197-2.5204 in)
Number of piston rings (compression / oil):2/1
Connecting rod small end diameter (standard):20.000-20.013 mm (0.7874-0.7879 in)
Piston pin diameter:20.002-20.011 mm (0.7875-0.7878 in)
Side clearance (Second):0.085-0.112 mm (0.0033-0.0044 in)
Side clearance (Oil):0.020-0.055 mm (0.0008-0.0022 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):0.200-0.400 mm (0.0079-0.0157 in)
Ring width (Second):1.458-1.470 mm (0.0574-0.0579 in)
Ring width (Oil):3.975-3.990 mm (0.1565-0.1571 in)
Number of main bearings:4
Crankshaft main journal diameter:43.934-43.950 mm (1.7297-1.7303 in)
Crankpin journal diameter:36.959-36.975 mm (1.4551-1.4557 in)
Cylinder head
Valves:2,(6 valves in total)
Valve timing (INTAKE):
Valve timing (EXHAUST):
Valve seat width (INTAKE):2.120 mm (0.0835 in)
Valve seat width (EXHAUST):2.120 mm (0.0835 in)
Value seat angle (INTAKE):45°
Value seat angle (EXHAUST):45°
Valveface angle (INTAKE):45.5°
Valveface angle (EXHAUST):45.5°
Valve steam diameter (INTAKE):6.960-6.975 mm (0.274-0.2746 in)
Valve steam diameter (EXHAUST):6.960-6.975 mm (0.274-0.2746 in)
Valve spring free length (INTAKE):35.100-34.800 mm (1.3819-1.3701 in)
Valve spring free length (EXHAUST):35.100-34.800 mm (1.3819-1.3701 in)
Camshaft lobe height (INTAKE):26.880 mm (1.0583 in)
Camshaft lobe height (EXHAUST):26.880 mm (1.0583 in)
Camshaft journal diameter :32.934-32.950 mm (1.2966-1.2972 in)

Tightening torque

Tightening torque specs
Head cover cap nuts (M7x1.0):6.9-8.8 Nm (0.7-0.9 kgf-m, 5.1-6.5 lb-ft)
Head screws and nuts (M9x1.25):64.7-69.6 Nm (6.6-7.1 kgf-m, 47.7-51.4 lb-ft)
Main bearing case screw 1 (M7x1.0): Flange bolts 26.5-30.4 Nm (2.7-3.1 kgf-m, 19.5-22.4 lb-ft)
Non-flange bolt 19.6-23.5 Nm (2.0-2.4 kgf-m, 14.5-17.4 lb-ft)
Main bearing case screw 2 (M8x1.25):29.4-34.3 Nm (3.0-3.5 kgf-m, 21.7-25.3 lb-ft)
Flywheel screw (M10x1.25): Flange bolts 58.8-63.7 Nm (6.0-6.5 kgf-m, 43.4-47.0 lb-ft)
Non-flange bolt 53.9-58.8 Nm (5.5-6.0 kgf-m, 39.8-43.4 lb-ft)
Connecting rod screw (M7x0.75):26.5-30.4 Nm (2.7-3.1 kgf-m, 19.5-22.4 lb-ft)
Rocker arm bracket nuts (M7x1.0):16.7-20.6 Nm (1.7-2.1 kgf-m, 12.3-5.2 lb-ft)
Idle gear shaft screws (M6x1.0):9.8-11.3 Nm (1.00-1.15 kgf-m, 7.2-8.3 lb-ft)
Idle gear shaft screws (M6x1.0):9.8-11.3 Nm (1.00-1.15 kgf-m, 7.2-8.3 lb-ft)
Glow plugs (M10x1.25):19.6-24.5 Nm (2.0-2.5 kgf-m, 14.5-18.1 lb-ft)
Drain plug (M11x1.25):39.2-49.0 Nm (4.0-5.0 kgf-m, 28.9-36.2 lb-ft)
Nozzle holder assembly (M24x2.0):29.4-49.0 Nm (3.0-5.0 kgf-m, 21.7-36.2 lb-ft)
Nozzle holder and nozzle retaining nut:58.8-78.5 Nm (6.0-8.0 kgf-m, 43.4-57.9 lb-ft)
Nozzle holder mounting screw (M24x2.0):39.2-49.0 Nm (4.0-5.0 kgf-m, 28.9-36.2 lb-ft)
Crankshaft nut (M24x1.5):137.3-156.9 Nm (14.0-16.0 kgf-m, 101.3-115.7 lb-ft)

Service Data

Maximum speed:3,200 rpm
Idle speed:800 rpm
Cylinder compression
Cylinder compression pressure:31.5 kgf/cm2 (3.09 MPa, 448 psi)
Compression differential limit between cylinders:10% or less
Valve clearance
Intake valve clearance:0.15-0.20 mm (0.006-0.008 in)
Exhaust valve clearance:0.15-0.20 mm (0.006-0.008 in)
Oil system
Lubrication system:Forced lubrication by pump
Oil type:API CC or better
Oil capacity:3.9 liters (4.12 US.qts, 3.43 Imp. qts)
Oil filter:Full flow paper filter (cartridge type)
Oil pressure: At idle spped: 68 kPa (0.7 kgf/cm2, 10 psi)
At rated speed: 196-441 kPa (2.0-4.5 kgf/cm2, 29-64 psi)
Fuel system
Fuel injection pumpBosch K Type Mini Pump
Injection nozzleBosch throttle Type
Injection timing:25° B.T.D.C.
Fuel injection pressure13.73-14.71 MPa (140-150 kgf/cm2, 1991-2133 psi)
Cooling system
Type:Pressurized radiator, forced circulation with water pump
Thermostat’s valve opening temperature:80.5-83.5°C (176.9-182.3°F)
Temperature at which thermostat completely opens:95°C (203°F)
Coolant capacity:4.6 L (4.86 US. qt, 4.05 Imp. qt.)
Electrical system
Battery:12V, 45AH or equivalent
Starter mica undercut:0.5-0.8 mm (0.0197-0.0315 in)
Starter brush length:16.0 mm (0.6299 in)
Alternator (no-load voltage):AC 20V
Glow plug resistance:1.0-1.2 Ω


Manufacturer or BrandModels
KubotaB6100, B6100HST
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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