2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 68Get this manual
VALVE CLEARANCE ADJUSTMENT 8.Adjust: Valve clearance
INSP ADJ
Adjustment steps: Loosen the locknut 1Insert feeler gauge between the adjuster end and the valve endTurn the adjuster clockwise or counterclockwise with the valve adjusting tool until the proper clearance is obtainedValve adjusting tool: PNYM-08035, 90890-01311
the adjuster to prevent it from moving and then tighten the locknutLocknut: 20 Nm (2.0 kg, 14 ft lb)
Measure If
the valve clearancethe clearance is incorrect, repeat the above steps until the proper clearance is obtained