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Kubota BX23, BX23S, BX24, BX25, BX25D Transaxle - Checking and adjusting

Kubota BX23, BX23S, BX24, BX25, BX25D Transaxle - HST adjusting

Adjusting maximum speed

Speed control pedal should contact with adjusting bolt (Forward) and / or (Reverse), when depress the speed control pedal fully. Lift up the rear wheels safely by the rigid jacks. Shift the front wheel drive lever to OFF position. Depress the speed control pedal to the forward all the way and lengthen the stopper bolt (for the forward) until it touches the speed control pedal. Adjust the stopper bolt (for the forward) length and lock it securely. Stopper bolt length Forward 17.0 mm / 0.669 in. Adjust the stopper bolt (for the reverse) length and lock it securely. Stopper bolt length Reverse 17.5 mm / 0.689 in. Finally check the traveling speed or rear axle shaft rotation speed. If the measurement is not within the references, check the adjusting bolt length. Maximum rear axle shaft speed (At engine maximum speed and low range) - 52.2 min-1/52.2 rpm.

Adjusting HST neutral position

Place the wooden blocks at the front and the rear side of the wheels to prevent tractor from moving. Lift up the rear wheels and secure with rigid jacks. Remove the R.H. rear wheel from the Kubota BX23, BX23S, BX24, BX25, BX25D tractor. Shift the front wheel drive lever to the 4WD off position. Start the engine. Operate the engine at the maximum revolution. Shift the range shift lever to hi position. Loosen the locking screw. Depress the speed control pedal to forward speed position, and release the foot from the speed control pedal. Check that the rear axle (or the wheel) stops rotating. If the rear axle (or the wheel) does not stop rotating, move the position of the locking screw to the machine front side to stop rotating. Depress the speed control pedal to reverse speed position, and release the foot from the speed control pedal. Check the rear axle (or the wheel) stops rotating. If the rear axle (or the wheel) does not stop rotating, adjust the locking screw to stop rotating. After adjusting the neutral position, tighten the locking screw securely.

Checking and adjusting HST neutral spring (dynamic braking)

If Kubota BX23, BX23S, BX24, BX25, BX25D tractor moves on level ground with foot off the pedal, or, if the pedal is too slow in returning to neutral position when removing the foot from the pedal, adjust the HST neutral spring. The HST neutral spring located under the front right side of the fender can adjust returning speed of speed control pedal. Since the HST neutral spring tension is weakened, the HST tension should be checked and adjusted every 100 hours.

Checking the HST neutral spring tension

Start the engine and hold the maximum engine speeds. Operate the machine on the concrete level ground. Shift the range gear shift lever to hi position. Depress the speed control pedal to forward. Release the foot from the speed control pedal. Check the distance between the foot releasing point and the machine stopping point. If the distance is more than shown below, strengthen the HST neutral spring tension so that the machine will stop in the specified distance after releasing the foot from the speed control pedal. Distance specification 3 m / 10 ft.

Adjusting the HST neutral spring tension

Remove the step from the machine. Loosen the lock nut. Turn the adjusting nut half turn to pull the HST neutral spring. Tighten and lock the lock nut. Start the engine and check dynamic brake as mentioned former. If the machine will not stop with dynamic brake in the specified distance, adjust the neutral spring again. The feeling of dynamic braking can be adjusted by changing the arm position of damper. Length (M) of adjusting rod at shipping the machine from the factory specification - 10 mm / 0.39 in.

Kubota BX23, BX23S, BX24, BX25, BX25D Transaxle - Relief valve

Checking charge relief pressure

Remove the plug (R 1/4) from the front cover, then install the adaptor (R 1/4) and pressure gauge. Set the range gear shift lever to neutral position. Start the Kubota BX23, BX23S, BX24, BX25, BX25D engine and operate it at the maximum speed. Read the pressure gauge to measure the charge relief pressure. If the measurement is not within the factory specifications, check the charge relief valve and related hydraulic components. Charge relief pressure 0.55 to 0.75 MPa / 80 to 100 psi. Oil temperature 50C / 122F. When reinstalling the hexagon socket head plug, apply liquid lock (Three Bond 1324 or its equivalent) to the plug. Charge relief valve checking plug (R 1/4) - 30 to 44 Nm / 22 to 32 lbf-ft.

Checking high relief pressure (Forward)

Jack up the machine. Remove the hexagon socket head plug (R 1/4) from P2, then install the adapter, cable, and pressure gauge. Start the engine and operate it at maximum speed. Set the range gear shift lever to hi position. Depress the speed control pedal to forward, and read the pressure gauge to measure the high relief pressure. If the measurement is not the same as factory specification, check the high pressure relief valve and related hydraulic components. High relief pressure (Forward) (Oil temperature at 50C, 122F) - 20.1 to 21.1 MPa / 2920 to 3060 psi.

Checking high relief pressure (Reverse)

Jack up machine. Remove the hexagon socket head plug (R 1/4) from P1, then install the adapter, cable and, pressure gauge. Start the engine and operate it at maximum speed. Set the range gear shift lever to hi position. Depress the speed control pedal to reverse, and read the pressure gauge to measure the high relief pressure. If the measurement is not same as factory specification, check the high pressure relief valve and related hydraulic components. High relief pressure (Reverse) (Oil temperature at 50C, 122F) - 20.1 to 21.1 MPa / 2920 to 3060 psi. Hexagon socket head plug (P1 and P2 port) - 30 to 44 Nm / 22 to 32 lbf-ft.

Readjusting relief valve

When HST does not work due to its loose hexagon socket head screw - The relief pressure is set within the factory specification when shipped from the factory. But, for the purpose of after-sales services, as it is impossible to reset the pressure precisely as set in the factory, its setting range is defined as a slightly wider range within the variable specification. Relief pressure - 20.1 to 21.1 MPa / 2920 to 3060 psi. Variable specification - 15.0 to 20.0 MPa / 2180 to 2900 psi. Measure the pre-adjustment distance. Compress the spring of the relief valve with a relief valve assembling tool. Find the distance by turning the poppet with a screwdriver. Distance of relief valve (Forward) Reference value 39.10 to 39.20 mm / 1.540 to 1.543 in. Distance of relief valve (Reverse, D=1.5 mm orifice) 38.60 to 38.70 mm / 1.520 to 1.523 in. The distance changes by about 0.5 mm (0.02 in.) per one turn of the poppet.

Repeat the same operation a few times to find the distance as it is difficult to acquire at the first time. After finding the distance, hold the setscrew to a vice and fasten the hexagon socket head screw with specified torque. On this occasion, use a copper plate, etc. for the vice jaws not to damage the setscrew. Hexagon socket head screw - 25 to 29 Nm / 18 to 21 lbf-ft. Install the relief valve in the HST. Check the relief pressure as indicated in Checking high relief pressure (Forward) and Checking high relief pressure (Reverse). The distance is for refresh only. Make sure to check the relief pressure after readjustment. If the relief pressure does not fall within the readjustment pressure range, repeat the processes of the above. Relief valve readjusting pressure - 15.0 to 20.0 MPa / 2180 to 2900 psi. The pressure changes by 1.5 MPa (15 kgf/cm2, 210 psi) per 0.1 mm (0.004 in.) in distance.

Kubota BX23, BX23S, BX24, BX25, BX25D Transaxle - PTO clutch

Checking PTO clutch operating pressure

Lift the rear of the Kubota BX23, BX23S, BX24, BX25, BX25D tractor and remove the left rear wheel. Remove the plug (R 1/8), then install the adapter (R 1/8), cable and pressure gauge. Start the engine and set at maximum speed. Engine speed Oil temperature Maximum 45 to 55C113 to 131F). Move the PTO clutch lever to Engaged position, and measure the pressure. If the measurement is not same as factory specifications, check the PTO relief valve and related hydraulic components. PTO clutch operating pressure - 1.0 to 1.3 MPa / 150 to 180 psi. Tightening torque PTO clutch valve plug (R 1/8) 13 to 21 Nm / 9.4 to 15 lbf-ft.

Adjusting brake pedal free travel

Release the parking brake. Loosen the lock nut and turn the turnbuckle to adjust the rod length. Extend the turnbuckle one additional turn. Retighten the lock nut. Depress the brake pedal several times and make sure the brake pedal free travel is correct according to specification. Brake pedal free travel - 25 to 35 mm / 1.0 to 1.4 in.