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Kubota B1550, B6100, B6200 - Engine Service

B1550, B6200 tractors are equipped with a Kubota D850 3-Cylinder Diesel Engine. B6100 tractor is powered by D650 model.

Kubota B1550, B6100, B6200 Engine - Checking and Adjusting

Compression Pressure

After warming up the engine, stop it and remove the air cleaner, the muffler and all nozzle holders. Install a compression tester for diesel engines to nozzle holder hole. After making sure that the speed control lever is set at the stop position (Non-injection), run the engine at 200 to 300 rpm with the starter. Read the maximum pressure. Measure the pressure more than twice. If the measurement is below the allowable limit, check the cylinder, piston ring, top clearance, valve and cylinder head. Variances in cylinder compression values should be under 10%.

Top Clearance

Remove the nozzle holder. Lower the piston in the cylinder. Insert a high quality fuse from the nozzle holder hole on the piston except where it faces the valve or the combustion chamber insert. Rotate the flywheel until the piston is raised and lowered again. Take out the fuse carefully. Repeat three times with a new fuse in the other directions. Measure the thickness of the crushed fuse with vernier calipers. If the measurement is not within the factory specifications, check the oil clearance of the crank pin and clearance between the piston pin and bushing. Head gasket thickness (after retightened) - 1.05 to 1.15 mm (0.0413 to 0.0453 in). Protection - 0.25 to 0.55 mm (0.010 to 0.022 in).

Draining Cooling Water and Engine Oil

Never remove radiator cap until cooling water temperature is below its boiling point. Then loosen cap slightly to the stop to relieve any excess pressure before removing cap completely. Prepare a bucket. Open the drain cock to drain cooling water. Prepare an oil pan. Remove the drain plug to drain engine oil in the pan.

Air Cleaner and Muffler

Remove the air cleaner. Remove muffler retaining nuts to remove the muffler. Install the muffler gasket so that its steel side face the muffler.

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. When checking the oil level, make sure a Kubota B1550, B6100, B6200 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.

Kubota B1550, B6100, B6200 - Engine Oil Changing

After warming up, stop the Kubota D850/D650 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 10W or 10W-30.

Changing 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.

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.

Air Filter Cleaning

The air filter protects the engine from damaging dust and sand. It must therefore be cleaned regularly to avoid engine seizure. Clean out the dust from the filter cowling. Clean out the dust from the filter. When installing the filter cowling, check that the "top" sign is well at the top. The filter housing will otherwise leak air and particles will damage the filter.

Kubota B1550, B6100, B6200 Engine - Disassembly and Assembly

Cylinder Head Cover and Injection Pipe

Remove the cylinder head cover cap nuts. Remove the cylinder head cover. Check to see that the cylinder head cover gasket is not defective. Loosen the pipe damps. Remove the injection pipes.

Nozzle Holder Assembly

Remove the fuel overflow pipes. Loosen the lock nuts, and remove the nozzle holder assemblies with a nozzle holder socket wrench. Remove the copper gaskets on the seats.

Alternator and Fan Belt

Remove the alternator. Remove the fan belt. Check to see that there are no cracks on the belt surface. After reassembling the fan belt, be sure to adjust the fan belt tension.

Cylinder Head

Loosen the pipe band, and remove the water return pipe. Remove the cylinder head screws and nuts in the order, and remove the cylinder head. Remove the cylinder head gasket and O-ring. Replace the head gasket with a new one. Install the cylinder head, using care not to damage the O-ring. Tighten the cylinder head screws and nuts gradually in the order after applying engine oil. Retighten the cylinder head screws and nuts after running the engine for 30 minutes.

Rocker Arm and Tappets

Remove the rocker arm bracket mounting nuts. Remove the rocker arm as a unit. After reassembling the rocker arm, be sure to adjust the valve clearance. Remove the tappets from the crankcase. Before installing the tappets, apply engine oil thinly around them. Mark the cylinder number to the tappets to prevent interchanging.

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.

Kubota B1550, B6100, B6200 - Gear Case

Fuel Feed Pump and Injection Pump Cover

Loosen the pipe clamp and remove the fuel pipe from the injection pump side. Remove the fuel feed pump mounting nuts. Remove the fuel feed pump. Apply a liquid gasket to the both sides of fuel feed pump gasket. Remove the injection pump cover. Apply a liquid gasket to the both sides of injection pump cover gasket.

Injection Pump, Fuel Feed Pump and Speed Control Plate

The tip of wire is bent like the hook to hang governor springs. Remove the socket head screws, and remove the engine stop solenoid. 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 using the specific tool. Remove the fuel feed pump. Disconnect the start spring from the bracket using the specific tool. Remove the socket head screws and nuts, and remove the injection pump.

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 and Idle Gear

Remove the gear case. Apply a liquid gasket to both sides of the gear case gasket. Grease thinly to the oil seal, and install it, ensuring the Up does not come off. Remove the crankshaft collar. Remove the O-ring. Remove the crankshaft oil slinger. Remove the external snap ring. Remove the idle collar and idle gear. Remove the idle gear collar. When installing the idle gear, be sure to align the alignment marks on gears.

Camshaft and Fuel Camshaft

Align the round hole on the cam gear with the camshaft stopper mounting screw position. Remove the camshaft stopper mounting screws. Remove the cam gear and camshaft. Apply engine oil thinly to the camshaft before installation. Remove the fork lever holder mounting screws. Remove the fork lever assembly. Remove the fuel camshaft stopper. Remove the fuel camshaft and injection pump gear.

Kubota B1550, B6100, B6200 - Piston and Connecting Rod

Oil Pan

Remove the oil pan mounting screws. Remove the oil pan by lightly tapping the rim of the oil pan with a wooden hammer. Apply a liquid gasket to both sides of the oil pan gasket. To avoid uneven tightening, tighten mounting screws in diagonal order from the center.

Oil Strainer

Remove the oil strainer mounting screw. Remove the oil strainer. After cleaning the oil strainer, install it. Install the oil strainer, using care not to damage the O-ring.

Piston

Turn the flywheel, and bring the No.1 piston to the top dead center. Pull out the piston upward by lightly tapping it from the bottom of the crankcase with the grip of a hammer. 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. Do not change the combination of cylinder and piston. Make sure of the position of each piston by marking. For example, mark "1" on the No.1 piston. When inserting the piston into the cylinder, place the gap of the compression ring on the opposite side of the combustion chamber and stagger the gaps of the compression ring and oil ring making a right angle from the gap of the compression ring. Carefully insert the pistons using a piston ring compressor. Otherwise, their chrome-plated section may be scratched, causing trouble inside the liner.

Piston Ring and Connecting Rod

Remove the piston rings using a piston ring tool. Put the parting mark for example, on the piston head. 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 piston pin, immerse the piston in 80C 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 parting mark. Mark the same number on the connecting rod and the piston so as not to change the combination.

Kubota B1550, B6100, B6200 - Flywheel and Crankshaft

Oil Pump and Crank Gear

Remove the starter. Straighten the washer, and remove the nut. Pull out the oil pump drive gear with a puller. Remove the oil pump mounting bolts. Remove the oil pump. Remove the crank gear with a special-use puller set. Remove the feather key on the crankshaft. Check to see that the feather key is on the crankshaft. Heat the crank gear to approx. 80C (176F), and fit on the crankshaft.

Flywheel

Lock the flywheel not to turn using the flywheel stopper. Remove the flywheel screws, except for two which must be loosened and left as they are. Set a flywheel puller , and remove the flywheel. Apply engine oil to the flywheel screws.

Bearing case cover and crankshaft

Before disassembling, check the side clearance of crankshaft. Also check it during reassembly. Remove the bearing case cover mounting screws. Screw two removed screws into the screw hole of bearing case cover to remove it. Stretch the washer and remove the bearing case screw. Pull out the crankshaft. Install the crankshaft sub assembly, aligning the screw hole of main bearing case with the screw hole of cylinder block. Apply engine oil to the seat and thread of bearing case screw. After tightening it, bend the washer firmly. Install the bearing case cover to position the casting mark on it upward. Tighten the bearing case cover mounting screws with even force on the diagonal line.

Main Bearing Case Assembly

Be sure to install the thrust bearing with its oil groove facing outward. Remove the two bearing case screws, and remove the main bearing case assembly, being careful with the thrust bearing and crankshaft bearing 2. Remove the main bearing case assemblies as above. Clean the oil passage in the main bearing case. Apply dean engine oil on the crankshaft bearing 2 and thrust bearings. Install the main bearing case assemblies in the original positions. They are not interchangeable.

Kubota B1550, B6100, B6200 Engine Troubleshooting

When Kubota D850 engine is difficult to start

Fuel is thick and doesn't flow - Check the fuel oil tank and fuel oil filter. Remove water, dirt and other impurities. As all fuel oil will be filtered by the filter, if there should be water or other foreign matters on the filter, replace the filter.

Air or water mixed in fuel system - If air is in the fuel filter or injection lines, the fuel pump will not work properly. To attain proper fuel injection pressure, check carefully for loosened fuel lines, cap nut, etc. Loosen air vent screws atop fuel filter and fuel injection pump to eliminate all the air in the fuel oil system.

Thick carbon deposits on orifice of injection nozzle - This is caused when water or dirt is mixed in the fuel. Clean the nozzle injection piece, being careful not to damage the orifice. Check to see if nozzle is working properly or not. If not, install a new nozzle.

Valve clearance is incorrect - Adjust valve clearance.

Leaking valves - Grind valve.

Fuel injection timing is incorrect - Adjust injection timing.

Engine oil becomes thick in cold weather and engine cranks slow - Change grade of oil according to the weather (temperature).

Low compression - Bad valve or excessive wear of rings, pistons and liners cause insufficient compression. Replace with new parts.

Battery is discharged and the engine will not crank - Charge battery. Use decompression device. In winter, always remove battery from tractor, charge fully and keep indoors. Install in tractor at time of use.

When Kubota D850 engine lacks power

Air cleaner is dirty or Fuel filter is dirty - Clean the element every 100-200 hours of operation.

Carbon around orifice of nozzle piece - Clean orifice and needle valve, being very carefully not to damage the nozzle orifice. Check nozzle. If defective, replace with new parts.

Compression is insufficient. Leaking valves - Bad valve and excessive wear of rings, pistons and liners cause insufficient compression. Replace with new parts. Grind valves.

Fuel is insufficient - Check fuel system.

Overheating of moving parts - Check lube oil system. Check to see if lube oil filter is working properly. Filter screens or elements deposited impurities would cause poor lubrication. Clean screens. Check to see if bearing clearance are within factory specs. Check engine timing.

Valves out of adjustment - Adjust to proper valve clearance.

Fuel injection pressure is incorrect - Adjust to proper pressure.

When Kubota D850 engine suddenly stops

Leak of fuel - Check the fuel tank and refill if necessary. Also check the fuel system for air or leaks.

Bad nozzle - If necessary, replace with a new nozzle.

Moving parts are overheated due to shortage of lube oil or improper lubrication - Check amount of engine oil with dipstick. Check lubricating oil system. Check to see if element inside the lubricating oil filter has become old and clogged. If necessary, replace with new element. Check to see if the engine bearing clearances is within factory specs.

When Kubota D850 engine must be stopped immediately

Speed suddenly decreases or increases - Check the adjustments and timing of injection and the fuel system.

Unusual sound is heard suddenly - Check all moving parts carefully.

Color of exhaust suddenly turns dark - Check the fuel injection system, especially the fuel injection nozzle.

Bearing parts are overheated - Check the lubricating system.

Oil light lights up during operation - Check lubricating system. Check to see if the engine bearing clearances are within factory specs. Check the function of the regulating valve inside the oil filter. Check pressure switch. Check filter base gasket.

Starter does not function

Defective Alternator rectifier - Repair Alternator and replace defective rectifier. Dirty or corroded terminal contacts - Wash terminal with hot water and tighten well. Bad brushes, armature or field - Replace.