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Kubota DF972 Engine

General Technical Data

Kubota DF972 Engine Specifications

Engine Model ................ Kubota DF972
Engine Type ................ 4-cycle vertical three-cylinder OHV gasoline/LPG engine
Number of Cylinders ................ 3
Displacement, cu.in (cc) ................ 58.7 (962)
Engine Bore, in (mm) ................ 2.93 (74.5)
Engine Stroke, in (mm) ................ 2.90 (73.6)
Rated Engine Power (Gas), hp (kW) ................ 32.5 (24.2)
Rated Engine Power (LPG), hp (kW) ................ 31.0 (23.1)
Rated Engine Speed, rpm ................ 3600
Maximum Speed, rpm ................ 3950
Idle Speed, rpm ................ 1400-1600
Compression Ratio ................ 9.2:1
Firing Order ................ 1-2-3
Valve Arrangement ................ Overhead valve
Direction of Rotation ................ Counter-clockwise (viewed from flywheel)
Lubrication System ................ Forced lubrication by trochoid pump
Oil Filter ................ Full flow paper filter (cartridge type)
Cooling System ................ Forced circulation with water pump
Ignition System ................ Distributor less solid stage type
Electrical System Rating ................ 12V
Starting System ................ Electric starter

Fuel System

Fuel System Type ................ Carburetor
Carburetor Type ................ Fixed main jet
Governor Type ................ Mechanical, centrifugal ball
Fuel Type ................ Gasoline (86 or higher) or Standard Commercial LP Gas

Dimensions and Weight

Length, in (mm) ................ 17.8 (453)
Width, in (mm) ................ 16.4 (416)
Height, in (mm) ................ 19.8 (503)
Net Weight, lbs (kg) ................ 159 (72.0)

Kubota DF972 Maintenance Data

Cylinder Block and Valves

Cylinder Bore Inside Diameter (Maximum), in (mm) ................ 2.9397 (74.669)
Cylinder Compression, psi (MPa) ................ 185 (1.27)
Cylinder Head (Max. Out of Flatness), in (mm) ................ 0.002 (0.05)
Intake Valve Clearance, in (mm) ................ 0.006 (0.15)
Exhaust Valve Clearance, in (mm) ................ 0.007 (0.19)

Engine Oil and Filters

Engine Oil Type (Summer) ................ SAE 30, 10W-30
Engine Oil Type (Winter) ................ SAE 5W-30
API Service Classifications ................ SH or higher
Oil Capacity, qts (L) ................ 3.6 (3.4)
Oil Filter Part Number ................ HH150-32430
Air Filter Part Number ................ K1211-82320
Fuel Filter Part Number ................ 12581-43012

Carburetor Adjustment

Main Fuel ................ Not adjustable (Factory setting)
Idle Fuel ................ 1-1/2 turns out
Low Idle Speed, rpm ................ 1500±100
High Idle Speed, rpm ................ 3850±100

Ignition System

Spark Plug Type ................ NGK BKR4E
Spark Plug Gap, in (mm) ................ 0.024-0.027 (0.6-0.7)
Module Air Gap, in (mm) ................ 0.008-0.016 (0.20-0.40)
Ignition Timing, deg ................ 21 BTDC
Spark Plug Torque, Nm (ft-lbs) ................ 20 (14)

Service Intervals

Service Air Filter Element ................ Every 50 hours
Check and Adjust Spark Plug ................ Every 100 hours
Change Engine Oil ................ Every 200 hours
Replace Engine Oil Filter ................ Every 200 hours
Check LPG Tank Setting Condition ................ Every 200 hours
Check Carburetor Adjustment ................ Every 300 hours
Check and Adjust Valve Clearance ................ Every 1000 hours
Replace Spark Plug ................ Every 1000 hours
Checking Vacuum Lock Hose of LPG Vaporizer ................ Every 1000 hours
Replace Air Filter Element ................ Yearly

Kubota DF972 Service Data

Cylinder Block

Cylinder Bore Inside Diameter (Std), in (mm) ................ 2.9331-2.9338 (74.500-74.519)
Cylinder Bore Inside Diameter (Wear Limit), in (mm) ................ 2.9397 (74.669)
Connecting Rod Alignment, in (mm) ................ 0.002 (0.05)
Crankshaft Alignment, in (mm) ................ 0.0008 (0.02)
Crankshaft Main Journal Outside Diameter, in (mm) ................ 1.7297-1.7303 (43.934-43.950)
Crankshaft Main Bearing 1 Inside Diameter, in (mm) ................ 1.7317-1.7338 (43.984-44.040)
Crankshaft Main Bearing 2,3 Inside Diameter, in (mm) ................ 1.7315-1.7320 (43.978-43.993)
Crankshaft Journal to Crankshaft Bearing Oil Clearance, in (mm) ................ 0.0011-0.0023 (0.028-0.059)
Crank Pin Outside Diameter, in (mm) ................ 1.3370-1.3376 (33.959-33.975)
Crank Pin Bearing Inside Diameter, in (mm) ................ 1.3384-1.3489 (33.995-34.010)
Crankshaft Side Clearance, in (mm) ................ 0.0059-0.0122 (0.15-0.31)

Cylinder Head and Valves

Cylinder Head (Max. Out of Flatness), in (mm) ................ 0.002 (0.05)
Top Clearance, in (mm) ................ 0.0532-0.0649 (1.35-1.65)
Intake Valve Clearance, in (mm) ................ 0.0057-0.0072 (0.145-0.185)
Exhaust Valve Clearance, in (mm) ................ 0.0057-0.0072 (0.145-0.185)
Valve Stem Outside Diameter, in (mm) ................ 0.23496-0.23543 (5.968-5.980)
Valve Guide Inside Diameter, in (mm) ................ 0.23661-0.23721 (6.010-6.025)
Valve Guide To Stem Clearance (Std), in (mm) ................ 0.0018-0.00224 (0.030-0.057)
Valve Guide To Stem Clearance (Wear Limit), in (mm) ................ 0.0039 (0.10)
Valve Seat Width, in (mm) ................ 0.0835 (2.12)
Valve Spring Free Length, in (mm) ................ 1.24-1.25 (31.30-31.80)
Intake Valve Timing (Open/Close), deg ................ 20/45
Exhaust Valve Timing (Open/Close), deg ................ 50/15
Cam Height (Std), in (mm) ................ 1.0583 (26.88)
Cam Height (Wear Limit), in (mm) ................ 1.0563 (26.83)
Camshaft Journal Outside Diameter, in (mm) ................ 1.29662-1.29725 (32.934-32.950)
Camshaft Bearing Inside Diameter, in (mm) ................ 1.2992-1.3002 (33.000-33.025)

Piston and Piston Rings

Piston Pin Bore Inside Diameter (Std), in (mm) ................ 0.78839-0.78897 (20.025-20.040)
Piston Pin Bore Inside Diameter (Wear Limit), in (mm) ................ 0.7890 (20.050)
Piston Pin Outside Diameter (Std), in (mm) ................ 0.78748-0.78791 (20.002-20.013)
Piston Pin Outside Diameter (Wear Limit), in (mm) ................ 0.7871 (20.954)
Top Compression Ring to Groove Side Clearance, in (mm) ................ 0.0032-0.0047 (0.080-0.12)
Second Compression Ring to Groove Side Clearance, in (mm) ................ 0.0026-0.0039 (0.065-0.10)
Oil Ring to Groove Side Clearance, in (mm) ................ 0.0024-0.0059 (0.06-0.15)
Top Compression Ring End Gap, in (mm) ................ 0.0059-0.0130 (0.15-0.35)
Second Compression Ring End Gap, in (mm) ................ 0.012-0.017 (0.30-0.45)
Oil Ring End Gap, in (mm) ................ 0.0079-0.027 (0.20-0.70)
Ring End Gap (Wear Limit), in (mm) ................ 0.0492 (1.25)

Kubota DF972 Torque Specifications

Cylinder head cover cap nuts (M6x1.0), Nm (ft-lb) ................ 9.8-11.2 (7.2-8.3)
Cylinder head bolts (M8x1.25), Nm (ft-lb) ................ 40-44 (29-32)
Bearing case bolts 1 (M6x1.0), Nm (ft-lb) ................ 13-15 (9.4-11)
Bearing case bolts 2 (M7x1.0), Nm (ft-lb) ................ 27-30 (20-22)
Flywheel bolts (M10x1.25), Nm (ft-lb) ................ 54-58 (40-43)
Connecting rod bolts (M7x0.75), Nm (ft-lb) ................ 27-30 (20-22)
Rocker arm bracket nuts (M6x1.0), Nm (ft-lb) ................ 9.8-11.2 (7.2-8.3)
Idle gear shaft bolts (M6x1.0), Nm (ft-lb) ................ 9.8-11.2 (7.2-8.3)
Spark plug (M14x1.25), Nm (ft-lb) ................ 20-24 (15-18)
Drain plug (M12x1.25), Nm (ft-lb) ................ 33-37 (24-27)
Fan drive pulley bolt (M12x1.5), Nm (ft-lb) ................ 118-127 (86-94)

KUBOTA TRACTORS TROUBLESHOOTING
L235	L2501	L2550	L275	L3110
L3301	L35	L3710	L3901	L4310
L5030	M4700	M5700	M6040	M6800
M8200	M8540	M9000	MX5100	MX5200