Specifications, Service and Repair of Farm and Lawn Tractors

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Kubota B26, B2601, B2620, B2630 - Engine Maintenance

Kubota D1105 3-cyl diesel engine used in B26, B2601, B2620, B2630 tractors.



Kubota B26, B2601, B2620, B2630 Engine - Checks and Adjustments

Compression Pressure

Operate the D1105 engine until it is warmed up. Stop the engine. Remove the air cleaner, the muffler and all glow plugs (or nozzles). Set a compression tester with the adaptor to the glow plug hole (or nozzle hole). Nozzle Hole: Adaptor H / Glow Plug Hole: Adaptor L. After making sure that the stop lever is set at the stop position (non-injection), operate the engine with the starter and measure the compression pressure. Repeat steps 4 and 5 for each cylinder. If the measurement is below the allowable limit, apply a small amount of oil to the cylinder wall through the glow plug hole (or nozzle hole) and measure the compression pressure again. If the compression pressure is still less than the allowable limit, check the top clearance, valve clearance and cylinder head. If the compression pressure increases after applying oil, check the cylinder wall and piston rings.

Valves

Valve Clearance - Valve clearance must be checked and adjusted when engine is cold. Remove the head cover, the glow plugs and the timing window cover on the clutch housing. Align the "1TC" mark line on the flywheel and center of timing window so that the No. 1 piston comes to the compression top dead center. Check the following valve clearance marked with using a feeler gauge. If the clearance is not within the factory specifications, adjust with the adjusting screw. The "TC" marking line on the flywheel is just for No. 1 cylinder. There is no "TC" marking for the other cylinders. No. 1 piston comes to the T.D.C. position when the "TC" marking line is aligned with center of timing window on front case. Turn the flywheel 0.26 rad (15 degrees) clockwise and counterclockwise to see if the piston is at the compression top dead center or the overlap position. Now readjust the valve clearance. Finally turn the flywheel 6.28 rad (360 degrees) and align the "TC" marking line and the center of timing window. Adjust all the other valve clearance as required. After turning the flywheel counterclockwise twice or three times, recheck the valve clearance, firmly tighten the lock nut of the adjusting screw. Valve Seat Tightness - Set the injection nozzle to a nozzle tester. Raise the fuel pressure, and keep at 12.75 MPa (130 kgf/cm2, 1849 psi) for 10 seconds. If any fuel leak is found, replace the nozzle piece.

Kubota B26, B2601, B2620, B2630 - Lubrication System

Changing Engine Oil

Before changing oil, be sure to stop the D1105 engine. 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 bottom of the engine and drain the oil completely. Screw in the drain plug. Fill new oil up to upper notch on the dipstick. When using an oil of different manufacturer or viscosity from the previous one, remove all of the old oil. Never mix two different type of oil. Use the proper SAE Engine Oil according to ambient temperatures. Engine oil capacity - 3 L.

Engine Oil Pressure

Remove the engine oil pressure switch, and set an oil pressure tester. Start the engine. After warming up, measure the oil pressure of both idling and rated speeds. If the oil pressure is less than the allowable limit, check the following: engine oil insufficient, oil pump damaged, oil strainer clogged, oil filter cartridge clogged, oil gallery clogged, excessive oil clearance. After checking the engine oil pressure, tighten the engine oil pressure switch to the specified torque.

Replacing Engine Oil Filter Cartridge

Remove the oil filter cartridge with the filter wrench. Apply a slight coat of oil onto the 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.

Oil Pump



Rotor Lobe Clearance - Measure the clearance between lobes of the inner rotor and the outer rotor with a feeler gauge. If the clearance exceeds the factory specifications, replace the oil pump rotor assembly. Cylinder I.D: 78.000 to 78.019 mm / 3.0709 to 3.0716 in. Oversized cylinder liner I.D: 78.500 to 78.519 mm / 3.0906 to 3.0912 in. Clearance between Outer Rotor and Pump Body - Measure the clearance between the outer rotor and the pump body with a feeler gauge. If the clearance exceeds the factory specifications, replace the oil pump rotor assembly. Clearance between outer rotor and pump body - 0.100 to 0.180 mm / 0.00394 to 0.00708 in. Clearance between Rotor and Cover - Put a strip of plastigauge onto the rotor face with grease. Install the cover and tighten the screws. Remove the cover carefully, and measure the amount of the flattening with the scale and get the clearance. If the clearance exceeds the factory specifications, replace the oil pump rotor assembly. Clearance between rotor and cover - 0.025 to 0.075 mm / 0.00099 to 0.0029 in.

Kubota B26, B2601, B2620, B2630 - Cooling System

Fan Belt and Radiator

Fan Belt Tension - Measure the deflection, depressing the belt halfway between the fan drive pulley and dynamo pulley at specified force (98 N, 10 kgf, 22 lbf). If the measurement is not within the factory specifications, loosen the dynamo mounting screws and relocate the dynamo 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. Radiator Cap Air Leakage - Set a radiator tester and adaptor on the radiator cap. Apply the specified pressure 88 kPa (0.89 kgf/cm2, 12 psi), and measure the time for the pressure to fall to 59 kPa (0.61 kgf/cm2, 8.6 psi). If the measurement is less than the factory specification, replace the radiator cap. Radiator Water Leakage - Pour a specified amount of water into the radiator. Set a radiator tester and an adaptor and raise the water pressure to the specified pressure. Check the radiator for water leaks. For water leak from the pinhole, repair with the radiator cement. When water leak is excessive, replace the radiator.

Thermostat Valve Opening Temperature

Suspend the thermostat in the water by a string with its end inserted between the valve and seat. Heating the water gradually, read the temperature when the valve opens and leaves the string. Continue heating and read the temperature when the valve opens approx. 8 mm (0.3 in.). If the measurement is not within the factory specifications, replace the thermostat.

Flush Cooling System and Changing Coolant

Stop the D1105 engine and let cool down. To drain the coolant, open the radiator drain cock, and remove radiator cap. The radiator cap must be removed to completely drain the coolant. 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. Start and operate the engine for few minutes. Stop the engine. Check coolant level and add coolant if necessary. Install the radiator cap securely.

Kubota B26, B2601, B2620, B2630 - Fuel System

Fuel Injection Pressure

Set the injection nozzle to a 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, replace the adjusting washer in the nozzle holder to adjust it. Pressure variation with 0.01 mm (0.0004 in.) difference of adjusting washer thickness: Approx. 235 kPa (2.4 kgf/cm2, 34 psi).

Cleaning Fuel Filter

When operation period reaches approx. 100 hours, clean the fuel filter. This job should not be done in the field, but in a clean place so as to prevent dust from entering fuel system. Close the fuel filter cock. Unscrew and remove the screw ring, and remove the filter bowl, and rinse the inside with kerosene. Take out the element and dip it in the kerosene to rinse. After cleaning reassembling the fuel filter, keeping out dust and dirt. Bleed the fuel system. If dust and dirt enter the fuel, the fuel pump and injection nozzle are subject to wear. To prevent this, be sure to clean the fuel filter bowl periodically.

Bleeding Fuel System

Air must removed: When the fuel filter or lines are removed. When tank is completely empty. After the tractor has not been used for a long period of time. Bleeding procedure is as follows: Fill the fuel tank with fuel. Start the engine and run for about 30 seconds, and then stop the engine.

Kubota B26, B2601, B2620, B2630 - Injection Timing

Remove the injection pipes. Remove the engine stop solenoid. Turn the flywheel counterclockwise (facing the flywheel) until fuel flows from the delivery valve holder. Continue to turn the flywheel slowly, and stop it as soon as the fuel level at the tip of the delivery valve holder begins to increase. Check to see if the timing angle lines on the flywheel is aligned with the alignment mark. If the injection timing is out of adjustment, readjust the timing with shims. The sealant is applied to both sides of the shim (soft metal gasket shim). The liquid gasket is not required for assembling. Shims are available in thickness of 0.20 mm (0.0079 in.), 0.25 mm (0.0098 in.), 0.30 mm (0.012 in.), 0.35 mm (0.014 in.) and 0.175 mm (0.00689 in.). Combine these shims for adjustments. Addition or reduction of shim (0.025 mm, 0.00098 in.) delays or advances the injection timing by approx. 0.0044 rad (0.25 degrees). In disassembling and replacing the injection pump, be sure to use the same number of new shims with the same thickness. Injection timing - 0.2662 to 0.3272 rad (17.25 to 18.75 degrees) before T.D.C.

Fuel Tightness of Pump Element

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. Operate the starter to increase the pressure.

Fuel Tightness of Delivery Valve

Remove the engine stop solenoid. Remove the injection pipes and glow plugs. Set a pressure tester to the fuel injection pump. Install the injection nozzle jetted with the proper injection pressure to the injection pump pressure tester. Operate the starter to increase the pressure. Stop the starter when the fuel jets from the injection nozzle. After that, turn the flywheel by the hand and raise the pressure to approx. 13.73 MPa (140 kgf/cm2, 1991 psi). Now turn the flywheel back about half a turn (to keep the plunger free). Keep the flywheel at this position and clock the time taken for the pressure to drop from 13.73 to 12.75 MPa (from 140 to 130 kgf/cm2, from 1991 to 1849 psi). Measure the time needed to decrease the pressure from 13.73 to 12.75 MPa (from 140 to 130 kgf/cm2, from 1991 to 1849 psi). If the measurement is less than allowable limit, replace the pump with new one.



Nozzle Spraying Condition - Set the injection nozzle to a nozzle tester, and check the nozzle spraying condition. If the spraying condition is damaged, replace the nozzle piece. Nozzle Holder - Secure the nozzle retaining nut with a vise. Remove the nozzle holder, and remove parts inside. Assemble the nozzle in clean fuel oil. Install the push rod, noting its direction. After assembling the nozzle, be sure to adjust the fuel injection pressure.

Kubota B26, B2601, B2620, B2630 - Engine Service

Top Clearance

Remove the cylinder head. Move the piston up and stick a strip of fuse [1.5 mm dia. (0.059 in. dia.), 5.0 to 7.0 mm long (0.20 to 0.27 in. long)] on the piston head at three positions with grease so as to avoid the intake valve and the exhaust valve and the combustion chamber ports. Lower the piston, and install the cylinder head and tighten the cylinder head screws to the specified torque. Turn the flywheel until the piston exceeds top dead center. Remove the cylinder head, and measure the thickness of the squeezed fuses. If the measurement is not within the factory specifications, check the oil clearance between the crankpin and the crankpin bearing and between the piston pin and the small end bushing.

Cylinder Head Surface Flatness and Flaw

Clean the cylinder head surface. Place a straightedge on the cylinder head's four sides and two diagonal. Measure the clearance with a thickness gauge. If the measurement exceeds the allowable limit, correct it with a surface grinder. Top clearance - 0.55 to 0.75 mm / 0.022 to 0.029 in. Cylinder head screws - 64 to 68 Nm / 47 to 50 lbf-ft. Cylinder Head Flaw - Prepare an air spray red check. Clean the surface of the cylinder head with detergent. Spray the cylinder head surface with the red permeative liquid. Leave it five to ten minutes after spraying. Wash away the read permeative liquid on the cylinder head surface with the detergent. Spray the cylinder head surface with white developer. If flawed, it can be identified as red marks.

Valve Recessing

Clean the cylinder head surface, the valve face and the valve seat. Insert the valve into the valve guide. Measure the valve recessing with a depth gauge. If the measurement exceeds the allowable limit, replace the valve. If it still exceeds the allowable limit after replacing the valve, replace the cylinder head. Clearance between Valve Stem and Valve Guide - Remove carbon from the valve guide section. Measure the valve stem O.D. with an outside micrometer. Measure the valve guide I.D. with a small hole gauge, and calculate the clearance. If the clearance exceeds the allowable limit, replace the valves. If it still exceeds the allowable limit, replace the valve guide. Valve recessing - 0.050 (protrusion) to 0.25 (recessing) mm / 0.0020 (protrusion) to 0.0098 (recessing) in. Clearance between valve stem and valve guide - 0.035 to 0.065 mm / 0.0014 to 0.0025 in. Valve stem O.D - 6.960 to 6.975 mm / 0.2741 to 0.2746 in. Valve guide I.D - 7.010 to 7.025 mm / 0.2760 to 0.2765 in.

Kubota B26, B2601, B2620, B2630 - Replacing Valve Guide

Press out the used valve guide using a valve guide replacing tool. Clean a new valve guide and valve guide bore, and apply engine oil to them. Press in a new valve guide using a valve guide replacing tool. Ream precisely the I.D. of the valve guide to the specified dimension. Valve Seating - Coat the valve face lightly with prussian blue and put the valve on its seat to check the contact. If the valve does not seat all the way around the valve seat or the valve contact is less than 70 %, correct the valve seating as follows. If the valve contact does not comply with the reference value, replace the valve or correct the contact of valve seating. Valve guide I.D (Intake and exhaust) - 7.010 to 7.025 mm / 0.2760 to 0.2765 in. Valve seat width - 2.12 mm / 0.0835 in.

Correcting Valve and Valve Seat

Before correcting the valve and the seat, check the valve stem and the I.D. of valve guide section, and repair them if necessary. After correcting the valve seat, be sure to check the valve recessing. Correct the valve with a valve refacer. Slightly correct the seat surface with a 0.79 rad (45 degrees) / 1.0 rad (60 degrees) valve seat cutter. Fitting the valve, check the contact position of the valve face and seat surface with prussian blue. Visual check - If the valve has been used for a long period, the seat tends to come in contact with the upper side of the valve face. Grind the upper surface of the seat with a 0.52 rad (30 degrees) valve seat cutter until the valve seat touches to the center of the valve face. Grind the seat with a 0.26 rad (15 degrees) valve seat cutter again, and visually recheck the contact between the valve and the seat. Repeat steps 3 and 4 until the correct contact is achieved. Continue lapping until the seated rate becomes more than 70 % of the total contact area.

Valve Lapping

Apply compound evenly to the valve lapping surface. Insert the valve into the valve guide. Lap the valve onto its seat with a valve flapper or screwdriver. After lapping the valve, wash the compound away and apply oil, then repeat valve lapping with oil. Apply prussian blue to the contact surface to check the seated rate. If it is less than 70 %, repeat valve lapping again. When valve lapping is performed, be sure to check the valve recessing and adjust the valve clearance after assembling the valve. Valve face angle: IN. 1.0 rad / 60 degrees, EX. 0.79 rad / 45 degrees. Valve seat angle: IN. 1.0 rad / 60 degrees, EX. 0.79 rad / 45 degrees.

Free Length and Tilt of Valve Spring

Measure the free length of valve spring with vernier calipers. If the measurement is less than the allowable limit, replace it. Put the valve spring on a surface plate, place a square on the side of the valve spring. Check to see if the entire side is in contact with the square. Rotate the valve spring and measure the maximum tilt. If the measurement exceeds the allowable limit, replace it. Check the entire surface of the valve spring for scratches. If there is any problem, replace it. Valve Spring Setting Load - Place the valve spring on a tester and compress it to the same length it is actually compressed in the engine. Read the compression load on the gauge. If the measurement is less than the allowable limit, replace it.

Oil Clearance between Rocker Arm and Rocker Arm Shaft

Measure the rocker arm shaft O.D. with an outside micrometer. Measure the rocker arm I.D. with an inside micrometer, and then calculate the oil clearance. If the oil clearance exceeds the allowable limit, replace the rocker arm and measure the oil clearance again. If it still exceeds the allowable limit, replace also the rocker arm shaft. Tilt Allowable limit - 1.0 mm / 0.039 in. Free length - 37.0 to 37.5 mm / 1.46 to 1.47 in. Oil clearance between rocker arm and rocker arm shaft - 0.016 to 0.045 mm / 0.00063 to 0.0017 in. Rocker arm shaft O.D - 11.973 to 11.984 mm / 0.47138 to 0.47181 in. Rocker arm I.D - 12.000 to 12.018 mm / 0.47244 to 0.47314 in. Push Rod Alignment - Place the push rod on V blocks. Measure the push rod alignment. If the measurement exceeds the allowable limit, replace the push rod. Oil Clearance between Tappet and Tappet Guide Bore - Measure the tappet O.D. with an outside micrometer. Measure the I.D. of the tappet guide bore with a cylinder gauge, and calculate the oil clearance. If the oil clearance exceeds the allowable limit or the tappet is damaged, replace the tappet.

Kubota B26, B2601, B2620, B2630 - Idle Gear

Timing Gear Backlash - Set a dial indicator (lever type) with its tip on the gear tooth. Move the gear to measure the backlash, holding its mating gear. If the backlash exceeds the allowable limit, check the oil clearance of the shafts and the gear. If the oil clearance is proper, replace the gear. Push rod alignment Allowable limit - 0.25 mm / 0.0098 in. Oil Clearance between tappet and tappet guide bore - 0.020 to 0.062 mm / 0.00079 to 0.0024 in. Tappet O.D - 19.959 to 19.980 mm / 0.78579 to 0.78661 in. Tappet guide bore I.D - 20.000 to 20.021 mm / 0.78740 to 0.78822 in. Backlash between idle gear 1 and crank gear - 0.0320 to 0.115 mm / 0.00126 to 0.00452 in. Backlash between idle gear 1 and cam gear - 0.0360 to 0.114 mm / 0.00142 to 0.00448 in. Backlash between idle gear 1 and injection pump gear - 0.0340 to 0.116 mm / 0.00134 to 0.00456 in. Idle gear 1 and idle gear 2 - 0.0330 to 0.117 mm / 0.00130 to 0.00460 in. Idle Gear 1 and 2 Side Clearance - Set a dial indicator with its tip on the idle gear. Measure the side clearance by moving the idle gear to the front and rear. If the measurement exceeds the allowable limit, replace the idle gear collar.

Camshaft

Camshaft Side Clearance - Set a dial indicator with its tip on the camshaft. Measure the side clearance by moving the cam gear to the front to rear. If the measurement exceeds the allowable limit, replace the camshaft stopper. Camshaft Alignment - Support the camshaft with V blocks on the surface plate at both end journals. Set a dial indicator with its tip on the intermediate journal. Measure the camshaft alignment. If the measurement exceeds the allowable limit, replace the camshaft. Cam Height - Measure the height of the cam at its highest point with an outside micrometer. If the measurement is less than the allowable limit, replace the camshaft. Idle gear 1 and 2 side clearance - 0.20 to 0.51 mm / 0.0079 to 0.020 in. Camshaft side clearance - 0.070 to 0.22 mm / 0.0028 to 0.0086 in. Camshaft alignment Allowable limit - 0.01 mm / 0.0004 in. Cam height of intake - 28.80 mm / 1.134 in. Cam height of exhaust - 29.00 mm / 1.142 in. Oil Clearance of Camshaft Journal - Measure the camshaft journal O.D. with an outside micrometer. Measure the cylinder block bore I.D. for camshaft with a cylinder gauge, and calculate the oil clearance. If the oil clearance exceeds the allowable limit, replace the camshaft.

Piston and Connecting Rod

Piston Pin Bore I.D - Measure the piston pin bore I.D. in both the horizontal and vertical directions with a cylinder gauge. If the measurement exceeds the allowable limit, replace the piston. Oil clearance of camshaft journal - 0.050 to 0.091 mm / 0.0020 to 0.0035 in. Camshaft journal O.D - 35.934 to 35.950 mm / 1.4147 to 1.4153 in. Camshaft bearing I.D (Cylinder block bore I.D.) - 36.000 to 36.025 mm / 1.4173 to 1.4183 in. Piston pin bore I.D - 22.000 to 22.013 mm / 0.86615 to 0.86665 in. Oil Clearance between Piston Pin and Small End Bushing - Measure the piston pin O.D. where it contacts the bushing with an outside micrometer. Measure the small end bushing I.D. with an inside micrometer, and calculate the oil clearance. If the oil clearance exceeds the allowable limit, replace the bushing. If it still exceeds the allowable limit, replace the piston pin. Clean a new small end bushing and bore, and apply engine oil to them. Using a small end bushing replacing tool, press in a new bushing (service parts) taking care to see that the connecting rod oil hole matches the bushing hole. Oil clearance between piston pin and small end bushing - 0.014 to 0.038 mm / 0.00055 to 0.0014 in. Piston pin O.D - 22.002 to 22.011 mm / 0.86622 to 0.86657 in. Small end bushing I.D - 22.025 to 22.040 mm / 0.86713 to 0.86771 in. Oil clearance between piston pin and small end bushing (Spare parts) - 0.014 to 0.038 mm / 0.00056 to 0.0014 in. Small end bushing I.D (Spare parts) - 22.025 to 22.040 mm / 0.86713 to 0.86771 in.

Kubota B26, B2601, B2620, B2630 - Piston Rings

Piston Ring Gap - Insert the piston ring into the lower part of the cylinder (the least worn out part) with a piston. Measure the ring gap with a thickness gauge. If the measurement exceeds the allowable limit, replace the piston ring. Clearance between Piston ring and Piston Ring Groove - Clean the rings and the ring grooves, and install each ring in its groove. Measure the clearance between the ring and the groove with a feeler gauge or depth gauge. If the clearance exceeds the allowable limit, replace the piston ring. If the clearance still exceeds the allowable limit with new ring, replace the piston. Piston ring gap: Top ring - 0.15 to 0.25 mm / 0.0059 to 0.0098 in. Second ring - 0.40 to 0.55 mm / 0.016 to 0.021 in. Oil ring - 0.25 to 0.45 mm / 0.0091 to 0.017 in. Clearance between piston ring and piston ring groove: Second ring - 0.0950 to 0.122 mm / 0.00374 to 0.00480 in. Oil ring - 0.020 to 0.060 mm / 0.00079 to 0.0023 in.

Connecting Rod Alignment

Remove the crankpin bearing, and install the connecting rod cap. Install the piston pin in the connecting rod. Install the connecting rod on the connecting rod alignment tool. Put a gauge over the piston pin, and move it against the face plate. If the gauge does not fit squarely against the face plate, measure the space between the pin of the gauge and the face plate. If the measurement exceeds the allowable limit, replace the connecting rod.

Crankshaft

Crankshaft Side Clearance - Set a dial indicator with its tip on the end of the crankshaft. Measure the side clearance by moving the crankshaft to the front and rear. If the measurement exceeds the allowable limit, replace the thrust bearings. If the same size bearing is useless because of the crankshaft journal wear, replace it with an oversize one referring to the table. Crankshaft Alignment - Support the crankshaft with V blocks on the surface plate at both end journals. Set a dial indicator with its tip on the intermediate journal. Measure the crankshaft alignment. If the measurement exceeds the allowable limit, replace the crankshaft. Space between gauge pin face plate - Allowable limit 0.05 mm / 0.002 in. Crankshaft side clearance - 0.15 to 0.31 mm / 0.0059 to 0.012 in. Oversize 0.20 mm / 0.0079 in. The crankshaft journal must be fine-finished to higher than Rmax = 0.8S. Crankshaft alignment - Allowable limit 0.02 mm / 0.0008 in. Oil Clearance between Crankpin and Crankpin Bearing - Clean the crankpin and crankpin bearing. Put a strip of plastigauge on the center of the crankpin. Install the connecting rod cap and tighten the connecting rod screws to the specified torque, and remove the cap again. Measure the amount of the flattening with the scale, and get the oil clearance. If the oil clearance exceeds the allowable limit, replace the crankpin bearing.

Cylinder

Cylinder Wear - Measure the I.D. of the cylinder at the six positions with a cylinder gauge to find the maximum and minimum I.D.'s. Get the difference (Maximum wear) between the maximum and the minimum I.D.'s. If the wear exceeds the allowable limit, bore and hone to the oversize dimension. Visually check the cylinder wall for scratches. If deep scratches are found, the cylinder should be bored. Correcting Cylinder - When the cylinder is worn beyond the allowable limit, bore and hone it to the specified dimension. Replace the piston and piston rings with oversize ones. Oversize: 0.5 mm (0.02 in.). When the oversize cylinder is worn beyond the allowable limit, replace the cylinder block with a new one.

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