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Kubota B5200, B7100, B7100HST - Engine Service
Kubota B5200, B7100, B7100HST - Fuel System
Replacing Filter Element
B5200, B7100, B7100HST tractors are equipped with a Kubota D750 3
Cylinder Diesel Engine. Before replacing the filter element, shut-off
the fuel supply to the filter by turning the fuel cock lever straight up
and do the following: Loosen retaining ring from filter housing. Remove
filter cup and О-ring from filter housing. Remove filter element and
О-ring and then install a new element in its place. Thoroughly clean
filter cup. Be sure that O-ring seal is in good condition and install on
filter cup. Install filter cup, being careful not to overtighten
retaining ring. Turn on fuel supply. Open vent plug on filter. Tighten
plug when fuel flows free of bubbles.
Checking Nozzle Opening Pressure
Move the tester handle up and down to prime fuel. Measure the pressure
of fuel gushing out from the nozzle tip. If the measurement is not
within the reference value, adjust with the adjustment washer inside the
nozzle holder. An increase of every 0.1 mm (0,004 in.) of washer
thickness causes an approximate 980 kPa (10 kgf/cm2, 142 psi) increase
in fuel injection pressure.
Checking Injection Timing
Check fuel injection timing of the cylinder approaching the expansion
stroke by manually turning the engine flywheel. Check if fuel is
injected at the moment the mark on the flywheel. If fuel injection
timing is improper, adjust with shims to change the position of the
injection pump. If injection is too late take off shim. Each shim will
cause proceeding of 0.026 rad. (1.5°). Shim thickness: 0.12 to 0.18 mm
(0.0047 to 0.0071 in.). Reference value - Before TDC (Top Dead Center)
0.401 to 0.436 rad. (23° to 25°) (at the beginning of static injection).
Checking Fuel Pipe
If the damp is loose, apply oil to the threads and securely retighten
it. The fuel pipe is made of rubber and ages regardless of the period of
service. Change the fuel pipe together with the clamp every two years.
However, if the fuel pipe and damp are found to be damaged or
deteriorate earlier than two years, then change or remedy. After the
fuel pipe and the clamp have been changed, bleed the fuel system. When
bleeding fuel system - Fid the fuel tank with fuel, and open the fuel
cock. Loosen the air vent plug of the fuel filter a few turns. Screw
back the plug when bubbles do not come up any more. Open the air vent
cock on top of the fuel injection pump. Retighten the plug when bubbles
do not come up any more.
Fuel Filter Cleaning
Water and grit present in the fuel will be extracted by the fuel filter.
When the filter is blocked/full, turn off the fuel tap, remove and clean
the filter. Air must always be removed when refitting the filter as
follows: Turn the fuel filter to the ON position. Open the taps as
follows - At the top of the injection pump. At the top of the fitter.
Half fill the tank. Turn the filter tap off. Fill the tank up to the
top. Run the engine for one minute then stop it. Turn off the pump tap.
Only open the pump tap and filter tap when draining.
Cleaning Air Cleaner
The air cleaner uses a dry element. Never apply oil to it. Remove and
clean out the dust cup before it becomes balf full with dust. When the
air filter element is dusty, clean it. Change the element once a year or
every 6th cleaning. Install the air cleaner dust cup with "TOP”
indicated on the rear of the cup in the upside. If the dust cup is
mounted incorrectly, dust or dirt does not collect in the cup, and
direct attachment of the dust to the element will cause its life time to
shorten to a great extent.
Cleaning Air Filter Element
When dry dust adheres. Use dean dry compressed air on the inside of the
element. Air pressure at the nozzle must not exceed 690 kPa (7kgf/cm2,
100psi). Maintain reasonable distance between the nozzle and the filter.
Cleaning Fuel Filter
Close the fuel filter cock. Unscrew the screw ring and remove the cup,
and rinse the inside with kerosene.
Checking Nozzle Injection Pressure
Set the injection nozzle to the nozzle tester. Slowly move the tester
handle to measure the pressure at which fuel begins jetting out from the
nozzle. If the measurement is not within the factory specifications,
disassemble the injection nozzle, and change adjusting washer until the
proper injection pressure is obtained. If the spraying condition is
defective, replace the nozzle piece. Pressure variation with 0.1 mm
(0.0039 in.) difference of adjusting washer thickness. Approx. 981 kPa
(10 kgf/cm2, 142 psi).
Removing Pumps
Detach the fuel pump. Detach the hydraulic pump. Do not hit the cap of
idling limit apparatus. Remove the injection pump cover. Remove one end
of the governor spring from the fork lever and leave it there. Remove
the nuts and bolts holding the injection pump. Detach the injection
pump. To prevent the pump rack from being caught, detach the pump along
the removal groove. Count the number of the fuel injection timing
adjusting shims.
Kubota B5200, B7100, B7100HST - Engine Oil and
Oil Filter
Checking Kubota D750 Engine Oil Level
Level the engine. To check the oil level, draw out the dipstick, wipe it
clean, reinsert it, and draw it out again. Check to see that the oil
level lies between the two notches. If the level is too low, add new oil
to the specified level. When checking the oil level, make sure the
tractor is on a flat surface. It is impossible to check accurately if
the tractor is not level. Check the oil level before starting or more
than 3 minutes after the engine has stopped. At other times, the check
will not be accurate as oil stagnates in certain engine parts. When
using an oil of different maker or viscosity from the previous one,
drain old oil. Never mix two different types of oil.
Changing Engine Oil
After warming up, stop the engine. To change the used oil, remove the
drain plug at the bottom of the engine and drain off the oil completely.
Reinstall the drain plug. Fill the new oil up to the upper notch on the
dipstick. Change the type of engine oil according to the ambient
temperature. Above 25C - SAE 30 or 10W-30, 0C to 25C - SAE 20 or 10W-30,
Below 0C - SAE 10 W or 10W-30.
Changing Kubota D750 Engine Oil Filter
Cartridge
Remove the oil filter cartridge with a filter wrench. Apply engine oil
to the rubber gasket on the new cartridge. Screw the new cartridge in by
hand. Over-tightening may cause deformation of rubber gasket. After
cartridge has been replaced, engine oil normally decreases a little.
Check the oil level and add new oil to the specified level.
Removing Gear Case, Camshaft, and Oil Pump
Remove the four bolts holding the speed control plate. Lift the plate to
detach. Remove the start spring near the gear case with a pair of
cutting pliers. Remove tie fan drive pulley with a puller. Remove the
gear case. Make sure there are three O-rings inside the gear case.
Remove the idler gear. Remove the camshaft stopper. Remove the camshaft
by drawing out the cam gear. Remove the fuel camshaft stopper. Remove
the fork lever holder and fork lever assembly. Draw out the fuel
camshaft and the injection pump gear. Set a gear puller on the oil pump
drive gear. Draw out the gear. Remove the oil pump. Remove the crank
gear with a gear puller.
Kubota B5200, B7100, B7100HST - Cooling System
Radiator Cap Air Leakage
Set a radiator tester to the radiator cap. Apply the specified pressure
of 0.9 kgf/cm2 (98.1 kPa, 12.8 psi). Check if the pressure drop to less
than 0.6 kgf/cm2 (59 kPa, 9 psi) in 10 seconds. If the pressure is less
than the factory specification, replace it.
Thermostat
Remove the thermostat cover. Remove the thermostat. Apply a liquid
gasket only at the thermostat cover side of the gasket.
Kubota D750 Water Pump
Remove the fan and fan pulley. Remove the water pump from gear case
cover. Remove the water pump flange. Press out the water pump shaft with
the impeller on it. Remove the impeller from the water pump shaft.
Remove the mechanical seal. Replace the mechanical seal with new one.
Checking and Replenish Cooling Water
Remove the radiator cap and check to see that the cooling water level is
just bellow the port. If low, add clean water and antifreeze. Be sure to
close the radiator cap securely. If the cap is loose or improperly
closed, water may leak out and the engine could overheat. Do not use an
antifreeze and scale inhibitor at the same time.
Checking Fan Belt Tension and Checking Fan
Belt Damage
Check the fan belt for damage. Check if the fan belt is worn and sunk in
the pulley groove. Replace the fan belt if the belt is damaged or nearly
worn out and deeply sunk in the pulley groove. Press the Ian belt
between fan pulley and pulley with your finger at force of 98N (10 kgf,
22 Ibs). Check if the fan belt deflection is 7 to 9 mm (0.28 to 0.35
in.). If the deflection is not within the factory specifications, adjust
with the tension pulley adjusting bolts.
Kubota B5200, B7100, B7100HST - Cylinder Block
and Cylinder Head
Cylinder Block
Dry-type cylinder liners are pressure-fitted into the cylinders to
reduce distortion and uneven wear and provide less operating noise and
lower oil consumption. To minimize noise, each cylinder has its own
crank chamber. The tunnel-type cylinder block is also more durable.
Cylinder Head
Inlet and exhaust ports are of cross-flow type to prevent air expansion
due to exhaust heat. The spherical combustion chambers provide a vortex
flow of air which enters the combustion chamber to improve combustion
and reduce fuel consumption. The sheathed type glow plug heats quickly
and assures good starting.
Kubota D750 Cylinder Head Disassembly
Remove the head cover nuts. Remove the head cover. Loosen the tension
pulley shaft set nut. Loosen the tension bolt for the tension pulley and
remove the V-belt. Loosen the screws on the pipe clamp. Detach the
injection pipes in the order of 1, 2 and 3. Remove the clips holding the
fuel overflow pipes, and detach the pipes. Detach the nozzle holders
using a 27mm (1.063 in.) nozzle holder socket wrench. Remove the set
nuts for the rocker arm brackets, and detach the rocker arm assembly.
Remove the six push rods. Remove the twelve cylinder head bolts and two
nuts. Remove the cylinder head. Detach the cylinder head gasket, being
careful not to scratch it. Remove the О-ring from the periphery of the
oil pipe pin on the crankcase. Remove the six tappets from the
crankcase.
Checking Compression
Warm up the engine. Detach the air cleaner and the nozzle holders of all
cylinders. Attach compression tester to the cylinder to be measured. Run
the engine with the starter at engine speed 200 to 250 rpm and read the
constant maximum on the tester. Repeat the test at least twice. (Run the
engine for 5 to 10 seconds for each test.). Reference value: 2.7 to 3.1
MPa (28 to 32 kgf/cm2, 398 to 454 psi). Allowable limit: 2.4 Mpa (24
kgf/cm2,341 psi). When the reading is below the allowable limit, pour a
small amount of oil through the nozzle holder hole, and test again. If
the pressure recovers to the standard level after a while, the possible
cause of the in-adequate pressure is wearing or adhesion of piston
rings. Check related points. If the pressure does not recover, it may be
because of cylinder head or valve problems. Check related points. If
there is a difference in compression of more than 10 percent (%) among
the cylinders, trace the cause of pressure variation and take corrective
measures.
Checking Distortion of Cylinder Head Surface
Clean the surface of the cylinder head. Place a straight edge on the
four sides and diagonal lines of the cylinder head to check surface
straightness. Insert a feeler gauge between the straight edge and the
cylinder head surface. The maximum thickness that can be inserted is the
amount of distortion. Allowable limit: 0.05 mm (0.002 in.) per 100 mm (4
in.). Do not place a straight edge on the combustion chamber. If the
measurement exceeds the allowable limit, correct with a surface grinder.
Kubota B5200, B7100, B7100HST - Checking
Valves
Inlet and Exhaust Valves
The inlet and exhaust valves and their guides are different from each
other. Other parts, such as valve springs, valve spring retainers, valve
spring collets, valve stem seals, and valve caps are the same for both
the inlet and exhaust valves. All contact or sliding parts are quenched
and tempered to resist wear.
Checking Valve Recess
Clean the face of the valve. Measure the recess with a depth gauge. If a
valve seat is reground many times, it will recede too far and the valve
spring will stretch and lose its tension. When the valve recess becomes
more than the reference value, place a washer of appropriate thickness
under the spring. Reference value: 0.9 to 1.1 mm (0.035 to 0.043 in.).
Allowable limit: 1,3mm (0.051 in.).
Checking Stem Guide Clearance
Remove carbon from the valve guide. After making sure that the valve
stem is straight, insert the valve into the valve guide. Measure the
stem guide clearance with a dial gauge. If the measurement exceeds the
allowable limit, replace the stem guide and the valve. Reference value:
0.035 to 0.065 mm (0.0014 to 0.0026 in.). Allowable limit: 0.1 mm (0.004
in.). When replacing valve guides, make sure that they are installed on
the proper sides.
Checking Valve Spring Inclination
Put the spring on a surface plate, place a square on the side of the
spring, and check to see if the entire side is in contact with the
square. Rotate the spring and measure the maximum. The flat surface at
the end of the spring coil must be at least 2/3 more than the full
circumference. Check the entire surface of the spring for scratches. If
the measurement exceeds the allowable limit, replace the valve spring.
Allowable limit: 1.3 mm (0.051 in.).
Kubota B5200, B7100, B7100HST - Pistons,
Piston Rings and Crankshaft
Piston
Piston circumference has a special elliptic shape in consideration of
expansion due to explosion heat. Furthermore, a rib is provided between
the piston head and the piston boss to reduce distortion and to help
heat radiation. Three piston rings are used: two compression rings, and
an oil ring. All have different shapes. Be careful when assembling.
Crankshaft
The crankshaft is driven by the pistons and connecting rods, and
translates its reciprocating movement into a circular movement. It also
drives the oil pump, camshaft, and fuel camshaft. Crankshaft journals
are supported by main bearings. Six counterweights are integrated into
one unit to minimize bearing wear and lubricating oil temperature rise.
Crankshaft journals and the oil seal's sliding sections are quenched and
tempered to improve wear resistance.
Kubota D750 - Removing Piston and Crankshaft
Remove the eighteen oil pan mounting bolts, and detach the oil pan.
Detach the oil filter, being careful of the O-ring. Remove the
connecting rod bolts and large end metal, turn the crankshaft by 180°,
and bring the piston to top dead center. Draw out the piston upward by
lightly tapping it from the bottom of the crankcase with the handle of a
hammer. After drawing the piston out, attach a tag to each piston
indicating its number. Remove the piston rings. Set Flywheel Puller, and
remove the flywheel. Remove the bearing case cover mounting bolts. Screw
the two removed bolts into the right and left holes of the bearing case
cover, to pull off the cover by lifting it up. Detach the bearing case
bolts 2 under the crankcase. Draw out the crankshaft from the back of
the crankcase by lightly tapping it with a copper hammer. Detach the
main bearing cases, being careful with the side and crankshaft metals.
Grind the cylinder head mounting surface with an oil stone. Set the dry
liner centering base and adaptor on the frame head. Set the dry liner
centering base. Set the bearing cradle on the liner centering base with
the bearing on top. Insert the pulling-out adaptor coupling, and fix the
center bolt. Contact the pulling-out adaptor with the bottom of the
liner from the bottom of the crankcase. Pull out the liner by turning
the nut with a ratchet handle.
Checking Top Clearance
Remove the nozzle holder. Lower the piston in the cylinder to be
measured. Insert a high-quality fuse from the nozzle holder hole. Be
careful not to let the fuse touch the valve surface. Rotate the engine
by hand. Take the fuse out carefully. Measure the place where the fuse
was crushed with a set of vernier calipers. If the measurement is not
within the reference value, adjust by inserting a shim between the
cylinder head and the gasket. Reference value 0.6 to 0.8 mm (0.0237 to
0.031 5 in.).
Kubota B5200, B7100, B7100HST - Camshaft and
Rocker Arm
Camshaft and Fuel Camshaft
The camshaft is made of special cast iron and the journal and cam
sections are chilled to resist wear. The journal section is
force-lubricated. The fuel camshaft controls the reciprocating movement
of the injection pump and is equipped with a ball to control the
governor. The shaft end drives the hydraulic pump for implement lifting.
Fuel camshaft is made of carbon steel and journal and cam sections are
quenched and tempered to provide greater wear resistance.
Rocker Arm Assembly
The rocker arm assembly includes the rocker arms, rocker arm brackets
and rocker arm shaft, and converts the reciprocating movement of the
camshaft and push rods to an open/close movement of the inlet and
exhaust valves. Valve control timing must be adjusted with the screws on
the rocker arms. Lubrication oil is pressurized through the bracket to
the rocker arm shaft, which serves as a fulcrum so that the rocker arm
bearings and the entire system are lubricated sufficiently.
Checking Oil Clearance between Rocker Arm
Shaft and Bushing
Measure the inside diameter of the rocker arm bushings. Measure the
outside diameter of the rocker arm shaft and then calculate the
clearance. If the measurement exceeds the allowable limit, replace the
bushing. Rocker arm shaft O.D: 10.973 to 10.984 mm (0.4320 to 0.4324
in.). Rocker Arm bushing I.D: 10.997 to 11.038 mm (0.4330 to 0.4346
in.). Reference value: 0.013 to 0.065 mm (0.0005 to 0.0026 in.).
Allowable limit: 0.12 mm (0.0047 in.).
Checking Cam Heights of Intake and Exhaust
Place the camshaft on V-blocks. Attach a dial gauge to the journal.
While slowly rotating the camshaft, read the dial gauge. The camshaft
flexure is a half of the reading. If the measurement exceeds the
allowable limit, replace the camshaft. Allowable limit: 0.08 mm (0.0031
in.).
Checking Wear of Fuel Camshaft Cams
Place the fuel camshaft on V-blocks. Measure the cam height with a
micrometer. If the measurement exceeds the allowable limit, replace the
camshaft. Reference value: 30,93 to 31.07 mm (1.2177 to 1.2233 in.).
Allowable limit: 30.87 mm (1.2154 in.).
Checking Clearance between Idle Gear Shaft and
Idle Gear Bushings
Measure the idle gear shaft O.D. with an outside micrometer. Measure the
idle gear bushings I.D. with an inside micrometer, and calculate the
clearance. If the clearance exceeds the allowable limit, replace the
bushing. Reference value: 0.016 to 0.045 mm (0.0007 to 0.0017 in.).
Allowable limit: 0.1 mm (0.0039 in.).
Checking Backlash of Idler Gear
Install a lever-type indicator between the gear teeth. Read the
indicator while manually moving the gear. If the measurement exceeds the
allowable limit, replace the gear. Reference value: 0.04 to 0.12 mm
(0.002 to 0.005 in.). Allowable limit: 0.2 mm (0.008 in.).
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