Readjustment of Relief Valve (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 25.5 to 26.5 MPa (260 to
270 kgf/cm2, 3698 to 3840 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 22.6 to 26.5 MPa (230 to 270 kgf/cm2, 3271 to 3840
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 0.5 mm (0.0197 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 2-S7 and 2-S8.
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 1.47 MPa (15 kgf/cm2,
213.3 psi) per 0.1 mm (0.0039 in.) in distance A.
