Kubota L3301 L3901 Excavator Readjustment of Relief Valve

Here is the procedures for Kubota L3301 L3901 L4701 excavator relief valve readjustment.

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(When the HST does not work due to its loose hexagon socket head screw)
IMPORTANT
• The KUBOTA does not recommend the readjustment of relief valve. And KUBOTA will recommend the exhaust with genuine parts.
• As the HST may be damaged if the pressure is set to higher by mistake, be careful when adjusting it.
NOTE
• The relief pressure is set in between 33.4 to 36.2 MPa (340 to 370 kgf/cm2, 4840 to 5260 psi) 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
between 31.4 to 35.3 MPa (320 to 360 kgf/cm2, 4560 to 5120 psi).

1 Measure the pre-adjustment distance “A”.

2 Compress the spring of the relief valve with a relief valve assembling tool (3).

3 Then, find the distance “A” by turning the poppet (4) with a screwdriver.

Reference: The distance “A” changes by about 1.5 mm (0.02 in.) per one turn of the poppet (4).
4 Repeat the same operation a few times to find the distance “A” as it is difficult to acquire at the first time.

5 After finding the distance “A”, hold the setscrew (6) to a vice and fasten the hexagon socket head screw (2) with specified torque.

On this occasion, use a copper plate, etc. for the vice jaws not to damage the setscrew (6).
6 Install the relief valve in the HST.
7 Check the relief pressure as indicated in page 3-S14.The distance “A” is for refresh only. Make sure to check the relief pressure after readjustment.
8 If the relief pressure does not fall within the readjustment pressure range, repeat the processes of the above item 1 onward.
Reference: The pressure changes by 1.5 MPa (15 kgf/cm2,210 psi) per 0.1 mm (0.004 in.) in distance “A”

More repair case for Kubota,please refer to:Kubota Trouble Repair

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