Komatsu D65-12 D85-12 Bulldozer Main Control Valve Assembly Part Numbers: 723-63-21102, 723-63-21103, 723-63-21104, 723-63-22100 Common Faults & Troubleshooting A specific action is weak / not working: Stuck spool in that section, spool/sleeve wear causing internal leakage, damaged O-rings. First measure the outlet pressure of that section to diagnose. All actions are weak: Usually caused by insufficient main pump pressure or a failed main Relief Valve pressure setting. Check