Kubota U20-3 User Manual

U20-3, U25-3 WSM Hydraulic system (Service section)
IV-S-14
f. Traveling performance
In advance, make sure the trouble is in the travel mechanism alone.
Problem Cause Correction
Failure to run. (1) Travel lever linkage stuck or missing. Readjust the linkage or replace as required.
(2) Control valve spool stuck.
Overhaul and clean the control valve. Replace
as required.
(3) Internal leak in rotary joint. Overhaul the rotary joint. Replace the seal.
(4) Counterbalance valve spool stuck.
Overhaul and clean the counterbalance valve.
Replace as required.
(5) Too much motor drain.
Measure the drain amount. Overhaul the
motor. Replace as required.
(6) Motor internal parts damaged. Overhaul the motor. Replace as required.
Too slow travel speed.
Too low travel force.
(1) Travel lever linkage malfunctioning. Readjust the linkage.
(2) Control valve spool stuck.
Overhaul and clean the control valve. Replace
as required.
(3) Internal leak in rotary joint. Overhaul the rotary joint. Replace the seal.
(4) Counterbalance valve spool stuck.
Overhaul and clean the counterbalance valve.
Replace as required.
(5) Too much motor drain.
Measure the drain amount. Overhaul the
motor. Replace as required.
(6) Motor internal parts damaged. Overhaul the motor. Replace as required.
(7) Communicating valve spool stuck.
Clean the communicating valve. Replace as
required. Clean the filter.
Zigzagging.
(while traveling)
(1)
Right and left travel lever linkages out of
alignment.
Readjust the linkage.
(2)
Right and left control valve spools out of
alignment.
Overhaul and clean the control valve. Replace
as required.
(3) Internal leak in rotary joint on one side. Overhaul the rotary joint. Replace the seal.
(4) Counterbalance valve spool stuck.
Overhaul and clean the counterbalance valve.
Replace as required.
(5)
Too much difference between right and left
motor drain amounts.
Measure the drain amount. Overhaul the
motor. Replace as required.
(6) Internal parts damaged on motor on one side. Overhaul the motor. Replace as required.
If there is a difference in the flowrate and pressure between the right-travel and left-travel pumps,
check the delivery hoses on both sides. If one of them is in trouble, the machine travels zigzag. In this
case, other operations are also affected.
Failure to stop. (1) Travel lever linkage poor in return or stuck. Readjust the linkage.
(2) Control valve spool poor in return or stuck.
Overhaul and clean the control valve. Replace
as required.
(4)
Counterbalance valve spool poor in return or
stuck.
Overhaul and clean the counterbalance valve.
Replace as required.
Failure to shift the
gears.
(8)
Selector valve’s two-travel-speed switching in
trouble.
Overhaul and clean the selector valve.
Replace as required.
(9)
Travel motor’s high/low-speed switch spool
malfunctioning.
Overhaul and clean the high/low-speed
selector valve control. Replace as required.
(10) Limit switch malfunctioning. Check the limit switch. Replace as required.
(11) Solenoid and limit switch harness broken. Check the harness. Replace as required.

Kubota U20-3 Specifications

General

Brand	Kubota
Model	U20-3
Category	Excavators
Language	English