Specifications, Service and Repair of Farm and Lawn Tractors

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Kubota B1550, B1750 - HST Transmission


Kubota B1550, B1750 Hydrostatic Transmission - Speed Set Device

Speed Set Lever

Measure the force to move the speed set lever forward at its top (grip). If the force is not within the factory specification, turn the nut to adjust. After installing the spring, align the head of nut with the punched mark. Force to move the lever - 29.4 to 34.3 N (3.0 to 3.5 kgf / 6.6 to 7.7 lbs).

Setting Length of Lower Rod



1 - Speed Set Lever, 2 - Lower Rod, 3 - Yoke, 4 - Spring

Measure the length of lower rod (B). If the measurement is not within the factory specifications, adjust with the yoke of the lower rod. Setting length of lower rod - 178 mm 7.01 in.

Reverse Speed

Lift the rear of the tractor so that the rear wheels are off the ground. Set the engine speed at 2600 rpm and depress the differential lock pedal. If the rear wheels do not turn within the factory specifications, loosen the lock nut and adjust the bolt. Rear wheel rpm - 127 to 137 rpm (Engine at 2600 rpm).

Kubota B1550, B1750 HST Transmission - Checking And Adjusting

Neutral

Lift the rear of the tractor so that the rear wheels are off the ground and run the engine at low idling and drive only rear wheels. Depress the one end of speed control pedal and release, and do the same at the other end. If the rear wheels do not stop turning, adjust as following procedure. After taking off the cover, loosen the screw and be sure to place the neutral adjuster with its longer groove upward.

Adjusting Neutral

Rotate the neutral adjuster counterclockwise so that the rear wheels turn forward. Then rotate it clockwise until wheels stop completely. Put a mark on the clutch housing aligning the groove on neutral adjuster. Rotate the neutral adjuster clockwise so that the rear wheels turn reverse. Then rotate it counterclockwise until wheels stop completely. Put a mark on the clutch housing aligning the groove on neutral adjuster. Hold the neutral adjuster so that its groove is at the middle of the marks and tighten the screw. When the wheels tend to turn forward, rotate the neutral adjuster clockwise. When the wheels tend to turn reverse, rotate the neutral adjuster counterclockwise. Tightening torque neutral adjuster to case - 19 to 32 Nm (13 to 24 ft-lbs).

Oil Pressure in Hydrostatic Transmission

Clean and dear the work area, and fully engage the parking brake. Remove the knob screws (2) and sub cover (1). Measure the following oil pressures using Hydrostatic Transmission Testing Kit as instructed.



High Relief Pressure

Remove the M10 hex socket head plug from P1 or P2 port (P1 is for forward and P2 is for reverse). Install connector 2 to P1 (forward) or P2 (reverse) port. Assemble connector 1 and threaded joint with the gasket between them. Install the assembled connector 1 and threaded joint to connector 2. Install the cable, threaded joint in relief valve set pressure tester and high pressure gauge to threaded joint in order. Run the engine at 2600 rpm. Place the high-low shift lever in high. Depress the speed control pedal approx. 10 mm (0.39 in.) which rotates the trunnion shaft 0.087 rad (5.0°). High relief pressure (Oil temperature at 25 to 50C) - 22.6 to 24.5 MPa (3271 to 3555 psi). Measure quickly so that the relief valve may not be in operation more than 10 seconds. High pressure gauge is 30 MPa (4260 psi) full scale. Install the M10 plug to the port with the gasket laying on its seat. Plug (PI, P2 port) - 19.6 to 24.5 Nm (14 to 18 ft-lbs). Plug seat (P1, P2 port) - 54.9 to 58.8 Nm (41 to 43 ft-lbs).

Case and Case Relief Pressure

Remove the 1/4 plug from port, with care not to allow any particle of sealing tape enter into the port. Install the long connector to port with sealing tape on its thread. Install the threaded joint to long connector with the gasket between them. Install the cable, threaded joint in relief valve set pressure tester and low pressure gauge to threaded joint in order. Run the engine at 2600 rpm. Place the high-low shift lever in neutral. Release the speed control pedal to set in neutral. After measuring the case pressure, remove the eye joint from port and plug the port with 3/8 screw to measure the case relief pressure. Case relief pressure (Oil temperature at 25 to 50C) - 167 to 226 kPa (24.2 to 32.7 psi).

Charge Pressure

Remove the 1/4 plug from port, with care not to allow any particle of sealing tape enter into the port. Install the long connector to port with sealing tape on its thread. Install the threaded joint to long connector with the gasket between them. Install the cable, and threaded joint in order. Run the engine at 2600 rpm. Place the high-low shift lever in neutral. Release the speed control pedal to set in neutral. Charge pressure (Oil temperature at 25C) - 441 to 579 kPa (64.2 to 83,9 psi). Charge pressure (Oil temperature at 50C) - 421 to 559 kPa (61.1 to 81.1 psi).

Kubota B1550, B1750 HST - Parts Replacement

Hydrostatic Transmission

Remove the propeller shaft from the 1st shaft. Remove the drive shaft from the front wheel drive shaft (4WD type only). Loosen the hole clamp and remove the hose. Remove the HST mounting screws, and remove the HST. After inserting the spring pin into the 1st shaft and drive shaft, lock the spring pin with a wire. Be sure to replace the gasket with a new one.

Neutral Holder



1 - Screw, 2 - Neutral Holder, 3 - Neutral Adjuster, 4 - Neutral Holder Arm, 5 - Spring Holder

Place parting marks on the neutral adjuster (3) and the neutral holder arm (4). Remove the screws and spring holder (5). Remove the screw and the neutral holder arm (4). Remove the screw (1) and pull out the neutral holder (2). Aligning the parting marks, install the neutral adjuster and the neutral holder arm.

Front Wheel Drive Shaft 1 and Gears



1 - Hose Joint, 2 - 14T Gear, 3 - Front Wheel Drive Shaft 1, 4 - 16T Gear, 5 - Gasket

Pull out the front wheel drive shaft 1 (3) forward. Remove the external snap ring and 14T gear (2). Remove the external snap ring and 16T gear (4). Remove the hose joint (1) and gasket (5). Install the snap ring with its rounded edge facing the gear or bearing so that its sharp edge in the groove keeps itself in place against the force.

Port Block

Remove the port block mounting screws, and tap the front of port block flange with a soft hammer to separate. Cover the splines of each shaft with thin tape to protect the sealing lip. Install port block with gasket, О-ring and valve plate in place. Valve plates may stick to the port block, but they are not fixed . Take care not to drop them. Valve plates are not interchangeable. Valve plate of the pump has two notches and the valve of the motor has notches.

Motor Cylinder Block



1 - Output Shaft, 2 - Motor Cylinder Block, 3 - Piston, 4 - Retainer Plate, 5 - Retainer Holder

Hold the output shaft (1) and slightly tap the rear of case flange with a soft hammer to separate the motor cylinder block assembly. Slide out the motor cylinder block (2) with pistons (3), retainer plate (4) and retainer holder (5). Aligning the hole on the swashplate to the dowel pin in the case, and install the output shaft assembly in the case.

Pump Cylinder Block

Remove the internal snap ring retaining the retainer plate of pump. Slide out pump cylinder block with pistons retainer plate and internal snap ring. Draw out the thrust plate from the variable swashplate. Check that internal snap ring faces correct in the direction, and install it to pump swashplate. Squeeze the snap ring and slip into the hole its arc first by pushing down with a screwdriver to fit surely.

Charge Pump and Input Shaft

Remove the screws retaining the charge pump case. Tapping the rear end of the input shaft with a soft hammer, separate the charge pump case with the input shaft from the case. Remove two knock pins.

Pump Swashplate

Remove the screws retaining trunnion shaft cover. Tap the end of trunnion shaft with a soft hammer to separate the trunnion shaft cover 2. Tap the end of shaft with a soft hammer to separate the trunnion shaft cover 1. Install the trunnion shaft covers with the seam of bearing facing forward (machined surface side of case).

Kubota B1550, B1750 Tractor - HST Transmission Servicing

Input Shaft



1 - Seal Surface, 2 - Bearing Surface, 3 - Input Shaft, 4 - Bearing

Pull out input shaft (3) with the bearing on it from the charge pump case. Check the seal surface (1), the bearing surface (2) and the bearing (4). If the shaft is rough or grooved, replace. If the bearing is worn, replace.

Piston Slipper and Retainer Plate

Check the slipper for flatness. If rounded, replace. Measure the thickness of piston slipper. If the measurement is less than the allowable limit, replace. Check the lubricant hole for clogging. If dogged, open hole with compressed air. Thickness of slipper - 3.00 mm 0.118 in. Allowable limit - 2.90 mm 0.114 in.

Cylinder Block Face

Check the polished face of cylinder block for scoring. If scored, replace the cylinder block assembly. Check the spring for breakage. If broken, replace the cylinder block assembly.

Valve Plate

Check the engagement of the valve plate and the anchor pin. Pushing the valve plate against the anchor pin, lift it to remove. Check the valve place for foreign particles. Clean the valve plate and dry with compressed air. Check the valve plate for scratches, wear and erosion. If worn or scored, replace. Run a fingernail across the valve plate surface. If worn, it will be felt. After checking, coat them with hydrostatic transmission oil.

Swashplate and Thrust Plate

Check the bearing surface of trunnion shaft for scratches and excessive wear. If worn or scored, replace. Check the thrust plate for scratches and excessive wear. If worn or scored, replace.

Trunnion Shaft Cover

Check the bearings for scratches and excessive wear. If worn or scored, replace. Check the oil seal and the O-ring for damage. After checking, coat the bearing with hydrostatic transmission oil, and the oil seal lip and the О-ring with grease. When replace the oil seal, press it in the trunnion shaft cover until it is 1 mm (0.039 in.) below the shoulder and obtain the clearance under it.

Oil Seal and Bearing



1 - Oil Seal, 2 - Bearing, 3 - Flange 2, 4 - Oil seal, 5 - Bearing, 6 - Flange 1

Remove the flanges (3), (6) and check the oil seals (1), (4) for damage. Check the bearings (2), (5) for wear. If the bearings are worn, replace. After checking, coat the bearing with hydrostatic transmission oil and the oil seal lip with grease. When replacing the bearing, press it in the port block so that its mark faces outside and 3.5 mm (0.318 in.) of it remains above the machined surface. When reassembling, always replace the oil seal as follows. Press the oil seal (4) in the port block until it is 3 mm (0.118 in.) below the machined surface using the flange 1 (6). Press the oil seal (1) in the port block until so that 0.5 mm (0.020 in.) of it remains above the machined surface using the flange 2 (3).

Case Relief Valve

Check the valve and the spring for excessive wear and breakage. If worn or broken, replace. Length of valve spring (free) - 25.95 mm, 1.022 in. Length of valve spring (load 29.4 N) - 20.0 mm, 0 787 in. Length of valve spring (load 41.8 N) - 17.5 mm, 0089 in. The screw and the nut should be tightened fully, and then 3 to 3.5 mm (0.118 to 0.138 in.) of the thread on the screw will extend from the nut.

High Pressure Relief Valve



1 - Cap nut, 2 - Seat screw, 3 - Spring, 4 - Valve Seat, 5 - Poppet Valve, 6 - Backup Ring, 7 - O-ring, 8 - Backup Ring, 9 - O-ring, 10 - Port Block

Remove the cap nut (1). Put an alignment mark across the seat screw (2) and the port block (10) and measure its height from the port block to get the same setting pressure when reassembling. Remove the valve seat (4) using the valve seat driver, which is shown in figure. Check the poppet valve (5) for scratches and damage. Check the O-ring (7), (9) and the backup rings (6), (8) for damage. Check the spring (3) for breakage and wear. If anything unusual, replace the high pressure relief valve complete assembly. Length of valve spring (free) - 40.00 mm, 1.575 in. Length of valve spring (load 612 N) - 34.0 mm, 1.339 in. Length of valve spring (load 765 N) - 32.5 mm, 1.280 in. When reassembling, replace the O-ring and bonded seal. When the setting height of the seat screw (2) is not known, tighten it temporarily and adjust after reassembling the tractor. After reassembling the tractor, check the setting pressure and adjust by turning the set screw (2).

Neutral and Check Valves

Remove the valve assembly and disassemble it. Check the check valve and the neutral valve for their free movement on or in the valve body. If the valve surface is scored, replace. Check the holes of the valve body and the neutral valve for clogging. If clogged, open hole with compressed air. Check the O-rings and the backup ring for scratches and damage. Check the springs for breakage and wear. If anything unusual, replace. Length of valve spring (short) (neutral valve) - 19.71 mm, 0.7760 in. (free). Length of valve spring (long) (neutral valve) - 29.7 mm, 1.1691 in. (free). Length of valve spring (check valve) - 26.91 mm, 1.0594 in. (free).

Charge Relief Valve

Remove the internal snap ring and draw out the spring holder. Check the spring for breakage and wear. Check the O-ring for damage. If anything unusual, replace. Install the internal circlip with its sharp edge facing outside.

Charge Pump

Check the charge pump case, the plate and the gerotor set for scratches and wear. If scratched or worn, replace the charge pump complete assembly. Measure the side clearance referring to the figure. If the clearance exceeds the factory specification, replace the charge pump complete assembly. Side clearance - 0.030 to 0.060 mm (0.0018 to 0.0236 in). When reassembling, replace the О-rings and the oil seals, and grind the surface of the plate and the charge pump case with finest oil stone.

Reassembling



1 - Case, 2 - Bearing, 3 - Dowel Pin, 4 - Plate, 5 - Input Shaft, 6 - Key, 7 - Collar, 8 - O-ring, 9 - Dowel Pin, 10 - O-ring, 11 - Gerotor Set

Place the swashplate in neutral and install the input shaft (5) to the case (1) with the bearing (2) on it. Install the collar (7) on the bearing (2). Coat the O-rings (8), (10) with hydrostatic transmission oil and install them on the case (1). Install the dowel pins (3), (9) and the plate (4). Grind the key (6) with fine oil stone and install in it the groove of the input shaft (5). Install the gerotor set (11), noting the location of groove for the key.



1 - Snap Ring, 2 - Oil Seal, 3 - Plate, 4 - Charge Pump Case, 5 - O-ring, 6 - O-ring, 7 - Screw, 8 - Input Shaft, 9 - Gerotor Set, 10 - Plate

Coat the O-rings (5), (6) with hydrostatic transmission oil and install them on the charge pump case (4). Install the charge pump case (4) on the plate (10) and the gerotor set (9), and screw the screws (7) lightly. Press the plate (3) in the charge pump case (4). Cover the splines and the shoulder of the input shaft (8) with thin tape. Press the oil seal (2) in the charge pump case using the special tool, until it is 4 mm (0.157 in.) below the machined surface. Install the internal snap ring (1) with its sharp edge facing outside. Tighten the screws (7). Charge pump case to case tightening torque - 10.8 to 13.7 Nm (8.0 to 10.1 ft-lbs).

Kubota B1550, B1750 - Transmission Case Disassembly And Assembly

Fork Shaft and Shift Fork



1 - Fork Shaft Lock Screw, 2 - Shift Fork, 3 - Fork Shaft, 4 - Groove, 5 - Differential Gear Case

Remove the fork shaft lock screw (1). Screw M8 screw (pitch 1.25 x 70 mm long, pitch 1.25 x 2.76 in. long) into the fork shaft (3), and tap out it to the rear. Remove the shift fork (2). Install the fork shaft with the groove (4) facing the differential gear case (5).

Spiral Bevel Pinion Shaft

Remove the coupling. Remove the spiral bevel pinion with gears and bearings on it.

4th Shaft

Remove the external snap ring and shift the external snap ring forward. Tapping out the 4th shaft rearward, remove the 24T gear. Take out the 4th shaft with the gears and the bearing on it.

Front Wheel Drive Shaft

Remove the 23T gear. Remove the internal snap ring. Draw out the front wheel drive shaft.

2nd Shaft and 29T-14T-18T Gear

Remove the external snap ring. Remove 14T gear. Tap out the 2nd shaft rearward. Take out the 29T-14T-18T gear.

3rd shaft and 21Т, 21Т and 17Т Gear

Remove the internal snap ring. Tap out the 3rd shaft rearward. Take out the 21T, 21T and 17T gear.

Mid-PTO



1 - 24T Gear, 2 - Spring pin, 3 - Shaft, 4 - 11T Gear shaft, 5 - Snap ring, 6 - Oil seal

Separate the mid-PTO case from the transmission case After tapping the spring pin (2) into the shaft (3), remove the shaft (3) and the 24T gear (1). Remove the oil seal (6) and the external snap ring (5). Draw out the 11T gear shaft (4) with the bearing on it Plug tightening torque - 32.5 to 36.2 Nm (44 to 49 ft-lbs). Mid-PTO case to transmission case tightening torque - 48.0 to 55.9 Nm (35 to 41 ft-lbs).

Kubota B1550, B1750 - Transmission Case Service

Checking Bearing

Hold the inner race, and push and pull the outer race in all directions to check for wear and roughness. Apply transmission oil to the bearing, and hold the inner race. Then, turn the outer race to check rotation. If there is any defect, replace.

Backlash between Gear and Spline

Secure the shaft in a vise. Set a dial indicator (lever type). Move the gear by hand for measurement. If the measurement exceeds the allowable limit, replace it. Backlash between gear and spline - 0.03 to 0.08 mm (0.0012 to 0.003 in). Allowable limit - 0.20 mm (0.008 in).

Gear Backlash

Set a dial indicator (lever type) with its finger on the tooth surface. Move the gear to measure the backlash, while holding the mating gear. If the measurement exceeds the allowable limit, replace. Gear backlash - 0.10 to 0.20 mm (0.004 to 0.008 in). Allowable limit - 0.4 mm (0.016 in).

Clearance between Shift Fork and Shift Gear Groove

Place the shift fork in the shift gear groove and measure the clearance with a feeler gauge. If the clearance exceeds the allowable limit, replace. Clearance between shift fork and gear groove - 0.10 to 0.30 mm (0.004 to 0.012 in). Allowable limit - 0.5 mm (0.020 in).

Clearance between 29T-14T-18T Gear and 2nd Shaft

Measure the 29T-14T-18T gear I.D. with an inside micrometer, and then 2nd shaft O.D. with an outside micrometer. Measure the O.D. of two needles in the needle bearing with an outside micrometer. Clearance is the difference between the gear I.D. and the sum of shaft O.D. and two needles O.D. If the clearance exceeds the allowable limit, replace. Clearance between 29T-14T-18T gear and 2nd shaft - 0.007 to 0.053 mm (0.0003 to 0.0021 in). Allowable limit - 0.1 mm (0.039 in). 2nd shaft O.D. - 21.987 to 22.000 mm (0.8656 to 0.8661 in). 19T-14T-18T gear I.D. - 28.007 to 28.028 mm (1.1026 to 1.1035 in). Needle O.D. - 29.94 to 30.00 mm (0.1179 to 0.1181 in).

Clearance between 21T, 17T Gear and 3rd Shaft

Measure the 21T, 17T gear I.D. with an inside micrometer, and then 3rd shaft O.D. with an outside micrometer. Measure the O.D. of two needles on the needle bearing with an outside micrometer. Clearance is the difference between the gear I.D. and the sum of shaft O.D. and two needles O.D. If the clearance exceeds the allowable limit, replace. Clearance between 21T, 17T gear and 3rd shaft - 0.007 to 0.053 mm (0.0003 to 0.0021 in). Allowable limit - 0.1 mm (0.039 in). 3rd shaft О. D. - 24.987 to 25.000 mm (0.9837 to 0.9843 in). 21T, 17T gear I.D. - 29.007 to 29.028 mm (1.1420 to 1.1428 in). Needle O.D. - 1.997to 2.000 mm (0.0786 to 0.0787 in).

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KUBOTA TRACTORS SPECIFICATIONS

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KUBOTA ENGINES DATA AND SERVICE SPECS

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KUBOTA FRONT END LOADERS

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