08-26-2025, 11:34 PM
Kubota’s SVL90-2 and Its Role in Compact Track Loader Evolution
Kubota’s SVL90-2 compact track loader was introduced as part of the company’s aggressive expansion into the North American construction market in the early 2010s. Kubota, founded in 1890 in Osaka, Japan, had long been known for its agricultural equipment, but the SVL series marked a turning point in its commitment to heavy construction. The SVL90-2, with a rated operating capacity of 2,800 lbs and a breakout force exceeding 7,000 lbs, quickly became a favorite among contractors for its reliability, hydraulic power, and operator comfort.
By 2015, Kubota had sold tens of thousands of SVL units across North America, with the SVL90-2 often deployed for land clearing, grading, and brush cutting. However, like any hydraulic machine, it’s not immune to wear, contamination, or control valve issues—especially when lift arms begin to drift or fail to hold position.
Terminology Clarification
The issue began during brush cutting operations. The attachment functioned normally, but the lift arms would not hold their raised position. Even without a load, the arms would slowly drift downward. No fault codes were present, and the hydraulic pump appeared to be functioning.
To isolate the problem, the operator performed a series of tests:
Common Causes of Hydraulic Drift
Hydraulic drift in lift arms can result from several factors:
Control Valve and Relief Cartridge Investigation
The control valve block on the SVL90-2 contains multiple relief cartridges, each tuned to specific pressure thresholds. The lift arm section includes overload relief valves that prevent excessive pressure buildup. If one of these valves fails or becomes contaminated, it can allow fluid to bypass the cylinder, causing drift.
The operator eventually identified one faulty relief valve in the lift arm section. After disassembling and cleaning it, the issue persisted. Swapping it with another valve from the bucket circuit temporarily resolved the lift arm problem but introduced drift in the bucket’s dig position.
This confirmed that the relief valve was the culprit. The part number (V0511-63640) carried a replacement cost of $588, prompting questions about rebuild options.
Rebuilding and Adjusting Relief Valves
Relief valves can often be disassembled for inspection. Common failure points include:
Adjustment of relief cartridges is possible but must be done cautiously. Threaded shafts control spring preload, which directly affects pressure thresholds. Matching thread exposure between cartridges can help maintain balance across circuits.
Spool Valve and Joystick Considerations
If relief valves are ruled out, attention should turn to the spool valve and joystick assembly. A leaking spool or misaligned centering spring can cause the valve to remain slightly open, allowing fluid to bypass. In rare cases, fragments of cylinder packing can float into the control valve, causing intermittent obstruction.
Checking for loose spool caps (items 050 or 060 in service diagrams) and ensuring proper spring tension can resolve these issues. Plugged drain passages can also mimic valve leakage symptoms.
Lessons from the Field and Operator Culture
One operator shared a story of a similar issue on a Bobcat T770. After weeks of troubleshooting, the problem was traced to a single O-ring in the pilot valve. The machine had been used for snow removal, and salt corrosion had compromised the seal. A $2 part had sidelined a $60,000 loader.
This underscores the importance of preventive maintenance and fluid cleanliness. Hydraulic systems operate under extreme pressure—often exceeding 3,000 psi—and even microscopic debris can cause valve malfunction.
Final Outcome and Operational Advice
After running the SVL90-2 for several weeks post-repair, the lift arm issue resolved itself, suggesting that residual debris had finally cleared from the valve seat. However, the bucket drift persisted slightly, a compromise the operator accepted.
For others facing similar issues, the following steps are recommended:
The Kubota SVL90-2 remains a workhorse in the compact loader segment, but its hydraulic systems demand respect and attention. Lift arm drift is rarely a catastrophic failure—it’s often a symptom of valve contamination or seal wear. With methodical diagnostics and a bit of field ingenuity, even complex issues can be resolved without resorting to full component replacement. And sometimes, the best tool is patience.
Kubota’s SVL90-2 compact track loader was introduced as part of the company’s aggressive expansion into the North American construction market in the early 2010s. Kubota, founded in 1890 in Osaka, Japan, had long been known for its agricultural equipment, but the SVL series marked a turning point in its commitment to heavy construction. The SVL90-2, with a rated operating capacity of 2,800 lbs and a breakout force exceeding 7,000 lbs, quickly became a favorite among contractors for its reliability, hydraulic power, and operator comfort.
By 2015, Kubota had sold tens of thousands of SVL units across North America, with the SVL90-2 often deployed for land clearing, grading, and brush cutting. However, like any hydraulic machine, it’s not immune to wear, contamination, or control valve issues—especially when lift arms begin to drift or fail to hold position.
Terminology Clarification
- Lift arms: The hydraulic arms that raise and lower the loader bucket or attachment.
- Relief valve: A hydraulic component that limits pressure to prevent damage; often adjustable.
- Spool valve: A directional control valve that routes hydraulic fluid to actuators.
- Joystick spool: The internal valve mechanism controlled by the operator’s joystick.
- Centering spring: A spring that returns the spool to neutral when the joystick is released.
The issue began during brush cutting operations. The attachment functioned normally, but the lift arms would not hold their raised position. Even without a load, the arms would slowly drift downward. No fault codes were present, and the hydraulic pump appeared to be functioning.
To isolate the problem, the operator performed a series of tests:
- Raised the boom and curled the bucket down to lift the front of the machine. The boom held firm.
- Lowered the boom and curled the bucket to lift the front again. The bucket held firm.
Common Causes of Hydraulic Drift
Hydraulic drift in lift arms can result from several factors:
- Internal leakage in the lift cylinders due to worn piston seals
- Faulty relief cartridges in the control valve block
- Spool valve leakage or misalignment
- Debris obstructing valve seats or drain passages
- Pilot pressure anomalies keeping the valve slightly open
Control Valve and Relief Cartridge Investigation
The control valve block on the SVL90-2 contains multiple relief cartridges, each tuned to specific pressure thresholds. The lift arm section includes overload relief valves that prevent excessive pressure buildup. If one of these valves fails or becomes contaminated, it can allow fluid to bypass the cylinder, causing drift.
The operator eventually identified one faulty relief valve in the lift arm section. After disassembling and cleaning it, the issue persisted. Swapping it with another valve from the bucket circuit temporarily resolved the lift arm problem but introduced drift in the bucket’s dig position.
This confirmed that the relief valve was the culprit. The part number (V0511-63640) carried a replacement cost of $588, prompting questions about rebuild options.
Rebuilding and Adjusting Relief Valves
Relief valves can often be disassembled for inspection. Common failure points include:
- Debris lodged in the seat area
- Damaged or unravelled makeup valve springs
- Worn seals or scoring on the valve body
Adjustment of relief cartridges is possible but must be done cautiously. Threaded shafts control spring preload, which directly affects pressure thresholds. Matching thread exposure between cartridges can help maintain balance across circuits.
Spool Valve and Joystick Considerations
If relief valves are ruled out, attention should turn to the spool valve and joystick assembly. A leaking spool or misaligned centering spring can cause the valve to remain slightly open, allowing fluid to bypass. In rare cases, fragments of cylinder packing can float into the control valve, causing intermittent obstruction.
Checking for loose spool caps (items 050 or 060 in service diagrams) and ensuring proper spring tension can resolve these issues. Plugged drain passages can also mimic valve leakage symptoms.
Lessons from the Field and Operator Culture
One operator shared a story of a similar issue on a Bobcat T770. After weeks of troubleshooting, the problem was traced to a single O-ring in the pilot valve. The machine had been used for snow removal, and salt corrosion had compromised the seal. A $2 part had sidelined a $60,000 loader.
This underscores the importance of preventive maintenance and fluid cleanliness. Hydraulic systems operate under extreme pressure—often exceeding 3,000 psi—and even microscopic debris can cause valve malfunction.
Final Outcome and Operational Advice
After running the SVL90-2 for several weeks post-repair, the lift arm issue resolved itself, suggesting that residual debris had finally cleared from the valve seat. However, the bucket drift persisted slightly, a compromise the operator accepted.
For others facing similar issues, the following steps are recommended:
- Test cylinder integrity by lifting the machine and observing drift
- Inspect and clean relief cartridges, noting thread positions
- Swap cartridges to isolate faults
- Check joystick spool centering springs and drain passages
- Maintain fluid cleanliness and replace filters regularly
The Kubota SVL90-2 remains a workhorse in the compact loader segment, but its hydraulic systems demand respect and attention. Lift arm drift is rarely a catastrophic failure—it’s often a symptom of valve contamination or seal wear. With methodical diagnostics and a bit of field ingenuity, even complex issues can be resolved without resorting to full component replacement. And sometimes, the best tool is patience.
