Hydraulic Main Control Valve 723-44-11201 723-44-11100 723-44-11101 for Komatsu WA600-6 Wheel Loader Common Failures and Diagnostics Boom weak / slow lifting, bucket curl insufficient - caused by worn spool, relief valve or LS valve Boom / bucket drift - check anti-drift valve and cylinder seals first All functions slow & low pressure - main relief valve, LS bypass or unloading valve stuck Jerky movement - contaminated oil, stuck pressure compensator or LS shuttle valve EPC