Specifications, Service and Repair of Farm and Lawn Tractors

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Kubota BX1880, BX1860, BX1800 Engine - Service and Check

Kubota D722 Three-cylinder diesel engine used in BX1880, BX1860, BX1800 tractors.



Kubota BX1880, BX1860, BX1800 Engine - Check and Maintenance

Checking 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. Be sure to keep the oil level between upper and lower limits of the dipstick. Too much oil may cause a drop in output or excessive blow-by gas. On the closed breather type engine in which mist is sucked through port, too much oil may caused oil hammer. While too little oil, may seize the engine’s rotating and sliding parts.

Checking and Replenish Coolant

Without recovery tank: Remove the radiator cap and check to see that the coolant level is just below the port. With recovery tank: Check to see that the coolant level lies between FULL and LOW. If coolant level is too low, check the reason for decreasing coolant. If coolant is decreasing by evaporation, replenish only fresh, soft water. If coolant is decreasing by leak, replenish coolant of the same manufacture and type in the specified mixture ratio (fresh, soft water and L.L.C.). If the coolant brand cannot be identified, drain out all of the remaining coolant and refill with a totally new brand of coolant mix.

Changing Engine Oil



Start and warm up the engine for approx. 5 minutes. Place an oil pan underneath the engine. To drain the used oil, remove the drain plug at the bottom of the engine and drain the oil completely. Screw the drain plug. Fill new oil up to upper line on the dipstick. When using an oil of different maker or viscosity from the previous one, remove all of the old oil. Never mix two different types of oil. Engine oil should have properties of API classification CD/CE/CF/CF-4/CG-4. Use the proper SAE Engine Oil according to ambient temperature. Upon an oil change, be sure to replace the gasket with new one. Above 25C (77F) - SAE 30 or SAE 10W-30, SAE 10W-40. 0C to 25C (32F to 77F) - SAE 20 or SAE 10W-30, SAE 10W-40. Below 0C (32F) - SAE 10W or SAE 10W-30, SAE 10W-40.

Kubota BX1880, BX1860, BX1800 - Replacing Oil Filter Cartridge

Remove the oil filter cartridge with the filter wrench. Apply a slight coat of oil onto the new cartridge gasket. To install the new cartridge, screw it in by hand. Over tightening may cause deformation of rubber gasket. After the new cartridge has been replaced, the engine oil normally decrease a little. Thus see that the engine oil does not leak through the seal and be sure to read the oil level on the dipstick. Then, replenish the engine oil up to the specified level.

Checking Fuel Hose

If the clamp is loose, apply oil to the threads and securely retighten it. The fuel hose is made of rubber and ages regardless of the period service. Change the fuel hose together with the clamp every two years. However, if the fuel hose and clamp are found to be damaged or deteriorate earlier than two years, then change or remedy. After the fuel hose and the clamp have been changed, bleed the fuel system. When bleeding fuel system - Fill the tank with fuel and open the 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. If equipped electrical fuel feed pump, turn the key to AC position and pump the fuel up for 10 to 15 seconds. If equipped mechanical fuel feed pump, set the stop lever on stop position and crank the engine for 10 to 15 seconds. Close securely the air vent cock after air bleeding. Always keep the air vent cock on the fuel injection pump closed except when air is vented, or it may cause the engine to stop.

Fan Belt Tension

Measure the deflection, depressing the belt halfway between the fan drive pulley and alternator pulley at specified force 98 N (10 kgf, 22 lbs). If the measurement is not within the factory specifications, loosen the alternator mounting screws and relocate the alternator to adjust.

Fan Belt Damage and Wear

Check the fan belt for damage. If the fan belt is damaged, replace it. Check if the fan belt is worn and sunk in the pulley groove. If the fan belt is nearly worn out and deeply sunk in the pulley groove, replace it.

Cleaning Air Cleaner Element

Remove the air cleaner element. Use clean dry compressed air on the inside of the element. Pressure of compressed air must be under 205 kPa (2.1 kgf/cm2, 30 psi). Maintain reasonable distance between the nozzle and the filter. The air cleaner uses a dry element. Never apply oil to it. Do not run Kubota D722 engine with filter element removed. Change the element once a year or every 6th cleaning.

Kubota BX1880, BX1860, BX1800 - Cleaning Fuel Filter

Close the fuel cock. Unscrew the retaining ring and remove the filter cup, and rinse the inside with kerosene. Take out the element and dip it in the kerosene to rinse. After cleaning, reassemble the fuel filter, keeping out dust and dirt. Bleed the fuel system. If dust and dirt enter the fuel, the fuel injection pump and injection nozzle will wear quickly. To prevent this, be sure to clean the fuel filter cup periodically.

Checking Radiator Hoses and Clamp Bands

Check to see if the radiator hoses are properly fixed every 200 hours of operation or every six months, whichever comes first. If the clamp is loose, apply oil to the threads and retighten it securely. The water hose is made of rubber and tens to age. It must be replaced every two years. Also replace the clamp and tighten it securely.

Checking Intake Air Line

Check to see if the intake air hose(s) and the breather hose are properly fixed every 200 hours of operation. If the clamp is loose, apply oil to the threads and retighten it securely. The intake air hose(s) and the breather hose are made of rubber and tends to age. It must be changed every two years. Also change the clamp and tighten it securely. To prevent serious damage to the engine, keep out any dust inside the intake air line.

Replacing Fuel Filter Cartridge (Cartridge Type)

Water and dust in fuel are collected in the filter cartridge. So, change the filter cartridge every 400 hours service. Remove the used filter cartridge with filter wrench. Apply a thin film of fuel to the surface of new filter cartridge gasket before screwing on. Then tighten enough by hand. Loosen the air vent plug to let the air out. Start engine and check for fuel leakage.

Replacing Fuel Filter Element (Element Type)

Close the fuel cock. Unscrew the retaining ring and remove the filter cup, and rinse the inside with kerosene. Replace the filter element. Reassemble the fuel filter, keeping out dust and dirt. Bleed the fuel system.

Cleaning Water Jacket and Radiator Interior

Stop a Kubota D722 engine and let cool down. To drain the coolant, open the radiator drain plug and remove the radiator cap. Then radiator cap must be removed to completely drain the coolant. And open the drain cock. After all coolant is drained, close the drain plug. Fill with clean water and cooling system cleaner. Follow directions of the cleaner instruction. After flushing, fill with clean water and anti-freeze until the coolant level is just below the port. Install the radiator cap securely. Fill with coolant up to FULL mark on the recovery tank. Start and operate the engine for few minutes. Stop the engine and let cool. Check coolant level of radiator and recovery tank and add coolant if necessary.

Replacing Fan Belt

Remove the alternator. Remove the fan belt. Replace new fan belt. Install the alternator. Check the fan belt tension. Deflection - 7.0 to 9.0 mm / 98 N 0.28 to 0.35 in. / 98 N (10 kgf, 22 lbs).

Checking Injection Pump

Remove the engine stop solenoid. Remove the injection pipes and glow plugs. Install the injection pump pressure tester to the injection pump. Install the injection nozzle jetted with the proper injection pressure to the injection pump pressure tester. Set the speed control lever to the maximum speed position. Run the starter to increase the pressure. If the pressure can not reach the allowable limit, replace the pump with new one or repair.

Replacing Intake Air Line

Loosen the clamp. Remove the intake air hose and clamp. Replace new intake air hose and new clamp. Tighten the clamp. To prevent serious damage to the engine, keep out any dust inside the intake air line.

Replacing Battery

Disconnect the negative terminal and positive terminal. Remove the battery holder. Remove the used battery. Replace the new battery. Tighten the battery holder. Connect the positive terminal. Connect the negative terminal.

Replacing Radiator Hoses and Clamp Bands

Drain the coolant. Loosen the clamp bands. Remove the upper hose and lower hose. Replace new upper / lower hose and clamp bands. Tighten the clamp bands. Fill with clean water and anti-freeze until the coolant level is just below the port. Install the radiator cap securely.

Kubota BX1880, BX1860, BX1800 - Engine Disassembly

Starter

Unscrew the C terminal nut, and disconnect the connecting lead. Unscrew the solenoid switch mounting nuts, and remove the solenoid switch. Remove the end frame cap. Remove the brake shoe, brake spring and gasket. Unscrew the through bolts, and remove the rear end frame. Remove the brush from the brush holder while holding the spring up. Remove the brush holder. Draw out the yoke from the starter drive housing. Draw out the armature with the drive lever.

Alternator

Remove the pulley. Remove the rear end cover. Remove the brush holder. Remove the IC regulator. Remove the four screws holding the stator lead wires. Remove the rectifier. Remove the rear end frame. Press out the rotor from drive end frame. Remove the retainer plate. Press out the bearing from drive end frame with a press and jig. Lightly secure the rotor with a vise to prevent damage, and remove the bearing with a puller.

Cylinder Head



Loosen the pipe clamps, and remove the water return pipe. Remove the cylinder head screw in the order. Lift up the cylinder head to detach. Remove the cylinder head gasket and O-ring. Replace the cylinder head gasket with a new one. Securely fit the O-ring to the pipe pin. Tighten the cylinder head screws after applying sufficient oil. Tighten the cylinder head screws in order. Tighten them uniformly, or the head may deform in the long run. Retighten the cylinder head screws after running the engine for 30 minutes. Cylinder Head Cover - Disconnect the breather hose. Remove the cylinder head cover screws. Remove the cylinder head cover. Check to see if the cylinder head cover gasket is not defective.

Injection Pipes

Loosen the screws to the pipe clamp. Detach the injection pipes. Sent compressed air into the pipes to blow out dust. Then, reassemble the pipes in the reverse order.

Nozzle Heat Seal Service Removal Procedure

Use a plus (phillips head) screw driver that has a diameter which is bigger than the heat seal hole (Approx. 6 mm (1/4 in.). Drive screw driver lightly into the heat seal hole. Turn screw driver three or four times each way. While turning the screw driver, slowly pull the heat seal out together with the injection nozzle gasket. If the heat seal drops, repeat the above procedure. Heat seal and injection nozzle gasket must be changed when the injection nozzle is removed for cleaning or for service.

Rocker Arm and Push Rod

Remove the rocker arm bracket screws. Detach the rocker arm assembly. Remove the push rods. When putting the push rods onto the tappets, check to see if their ends are properly engaged with the dimples.

Thermostat Assembly

Remove the thermostat cover mounting screws, and remove the thermostat cover. Remove the thermostat assembly. Apply a liquid gasket only at the thermostat cover side of the gasket.

Tappets

Remove the tappets from the crankcase. Visually check the contact between tappets and cams for proper rotation. If defect is found, replace tappets. Before installing the tappets, apply engine oil thinly around them. Do not change the combination of tappet and tappet guide.

Valves

Remove the valve caps. Remove the valve spring collet, pushing the valve spring retainer by valve spring replacer. Remove the valve spring retainer, valve spring and valve stem seal. Remove the valve. Wash the valve stem and valve guide hole, and apply engine oil sufficiently. After installing the valve spring collets, lightly tap the stem to assure proper fit with a plastic hammer.

Oil Pan and Oil Strainer

Remove the oil pan mounting screws. Remove the oil pan by lightly tapping the rim of the pan with a wooden hammer. Remove the oil strainer. After cleaning the oil strainer, check to see that the filter mesh in clean, and install it. Visually check the O-ring, apply engine oil, and install it. Securely fit the O-ring to the oil strainer. To avoid uneven tightening, tighten oil pan mounting screws in diagonal order form the center. Using the hole numbered “3”, install the oil strainer by mounting screw

Kubota BX1880, BX1860, BX1800 - Gear Case and Timing Gears

Injection Pump, Fuel Feed Pump and Speed Control Plate (for Energize to Stop Type Engine Stop Solenoid)

Remove the socket head screws and nuts, and remove the injection pump. Remove the screws and separate the speed control plate, taking care not to damage the governor spring. Disconnect the governor spring and remove the speed control plate. Remove the fuel feed pump. Hook the governor spring to the governor lever first and install the speed control plate. Be sure to place the copper washers underneath two screws (Two screws in the upper of the speed control plate). Position the slot on the fork lever just under the slot on the crankcase. Insert the injection pump so that the control rod should be pushed by the idling adjusting spring at its end and the pin on the rod engages with the slot on the fork lever. The sealant is applied to both sides of the soft metal gasket shim. The liquid gasket is not required for assembling. Addition or reduction of shim (0.05 mm, 0.0020 in.) delays or advances the injection timing by approx. 0.0087 rad (0.5°). In disassembling and replacing, be sure to use the same number of new gasket shims with the same thickness.

Injection Pump, Fuel Feed Pump and Speed Control Plate (for Energize to Run Type Engine Stop Solenoid)

Move the fork lever to the gear case side. Hook the start spring to the injection pump control rack pin. Put the specific tool through the fork lever hole of cylinder block and hook the start spring. Keep this spring slightly extended and install the injection pump. Make sure the control rod should be pushed by the idling adjusting spring and the pin on the rod engages with the fork lever. Hook the start spring to the bracket using the specific tool. Hook the governor springs (small and large) to the governor lever using the specific tool and install the speed control plate. Be sure to place the copper washers underneath two screws in the upper of the speed control plate. Install the engine stop solenoid rod to the guide hole of cylinder block and fix the engine stop solenoid with socket head screws.

Fan Drive Pulley

Secure the flywheel to keep it from turning. Remove the fan drive pulley screw. Draw out the fan drive pulley with a puller. Install the pulley to crankshaft, aligning the mark on them. Apply engine oil to the fan drive pulley retaining screw. And tighten it.

Gear Case

Disconnect the start spring from the fork lever 1. Remove the screw of inside the gear case and outside screws. Remove the gear case. Apply a liquid gasket to both sides of the gear case gasket. Be sure to set three O-rings inside the gear case.

Idle Gear

Remove the external snap ring, the collar and the idle gear. Remove the idle gear shaft mounting screws. Remove the idle gear shaft (if necessary). Apply engine oil to the idle gear shaft mounting screw. And tighten them. Install the idle gear, aligning the mark on the gears.

Camshaft

Remove the camshaft mounting screws and draw out the camshaft with gear on it. When install the camshaft, apply engine oil to the camshaft journals. Apply engine oil to the camshaft mounting screws. And tighten them.

Fuel Camshaft

Remove the retaining plate. Remove the fork lever holder mounting screws, then draw out the injection pump gear and fuel camshaft with the governor fork assembly. Hook the governor spring to the fork lever 2 before installing the fork lever assembly to the crankcase.

Oil Pump and Crankshaft Gear

Remove the oil pump gear. Remove the oil pump mounting screw and the oil pump. Remove the collar, O-ring and crankshaft oil slinger. Install the collar after aligning the marks on the gears.

Kubota BX1880, BX1860, BX1800 - Piston and Connecting Rod

Connecting Rod Cap

Remove the connecting rod caps using a bihexagonal 8 mm socket. Align the marks with each other (Face the marks toward the injection pump). Apply engine oil to the connecting rod screws and lightly screw it in by hand, then tighten it to the specified torque. If the connecting rod screw won’t be screwed in smoothly, clean the threads. If the connecting rod screw is still hard to screw in, replace it.

Piston

Turn the flywheel 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 grip of a hammer. Draw out the other pistons after the same method as above. Before inserting the piston into the cylinder, apply enough engine oil to the cylinder. When inserting the piston into the cylinder, face the mark on the connecting rod to the injection pump.

Piston Ring and Connecting Rod

Remove the piston rings using a piston ring tool. Remove the piston pin, and separate the connecting rod from the piston. When installing the ring, assemble the rings so that the manufacturer’s mark near the gap faces the top of the piston. When installing the oil ring onto the piston, place the expander joint on the opposite side of the oil ring gap. Apply engine oil to the piston pin. When installing the connecting rod to the piston, immerse the piston in 80C (176F) oil for 10 to 15 minutes and insert the piston pin to the piston. When installing the connecting rod to the piston, align the mark on the connecting rod to the fan-shaped concave.

Kubota BX1880, BX1860, BX1800 - Flywheel and Crankshaft

Flywheel

Secure the flywheel to keep it from turning using a flywheel stopper. Remove all flywheel screws and then remove the flywheel. Set the No. 1 crankpin at the top dead center (T.D.C.). Align the 1TC mark on the outer surface of the flywheel horizontally with the alignment mark on the rear end plate. Apply engine oil to the threads and the undercut surface of the flywheel screw and fit the screw.

Bearing Case Cover

Remove the bearing case cover mounting screws. First, remove inside screws and then outside screws. Remove the bearing case cover. Fit the bearing case gasket and the bearing case cover gasket with correct directions. Install the bearing case cover to position the casting mark UP on it upward. Apply engine oil to the oil seal lip and take care that it is not rolled when installing. Tighten the bearing case cover mounting screws with even force on the diagonal line.

Crankshaft Assembly

Remove the main bearing case screw 2. Turn the crankshaft to set the crankpin of the third cylinder to the bottom dead center. Then draw out the crankshaft until the crankpin of the second cylinder comes to the center of the third cylinder. Turn the crankshaft by 2.09 rad (120°) counterclockwise to set the crankpin of the second cylinder to the bottom dead center. Draw out the crankshaft until the crankpin of the first cylinder comes to the center of the third cylinder. Repeat the above steps to draw out all the crankshaft. Clean the oil passage of the crankshaft with compressed air. Install the crankshaft assembly, aligning the screw hole of main bearing case screw 2 with the screw hole of crankcase. When tightening the main bearing case 2, apply oil to the main bearing case screw 2 and screw by hand before tightening the specific torque. If not smooth to screw by hand, align the screw holes between the crankcase and the main bearing case.

Main Bearing Case Assembly

Remove the two main bearing case screws 1, and remove the main bearing case assembly 1, being careful with crankshaft bearing 3. Remove the main bearing case assembly 2 and the main bearing case assembly as above. Keep in mind, however, that the thrust bearing is installed in the main bearing case assembly. Clean the oil passage in the main bearing cases. Apply clean engine oil to the bearings. Install the main bearing case assemblies in original positions. Since diameters of main bearing cases vary, install them in order of marking from the gear case side. Match the alignment numbers on the main bearing case assembly 1. Do the same for the main bearing case assembly 2 and the main bearing case assembly too. When installing the main bearing case 1 and 2, face the mark FLYWHEEL to the flywheel. Install the thrust bearing with its oil groove facing outward.

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