2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 131Get this manual
CYLINDER HEAD
CYLINDER HEAD REMOVAL 1.Align: "T" mark (with stationary pointer)
Checking steps: Turn the crankshaft counterclockwise with wrenchAlign the "T" mark on the rotor with the stationary pointer on the crankcase coverWhen the "T" mark is aligned with the stationary pointer, the piston is at the Top Dead Center (T.D.CNOTE: When the piston is at the Top Dead Center (T.D.C on the compression stroke, there should be clearance between the valve stem tips and their respective rocker arm adjusting screwsIf there is no clearance, rotate the crankshaft counterclockwise one turn