2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 214Get this manual
RADIATOR
RADIATOR INSPECTION 1.Inspect: Radiator fins Obstruction CleanApply compressed air to the rear of the radiatorDamage Repair or replaceNOTE: Straighten any flattened fins with thin, flat-head screwdriver2.Inspect: Radiator hoses Cracksdamage Replace
3.Measure: Radiator cap opening pressure Below the specified pressure Replace the radiator capRadiator cap opening pressure: 93.3122.7 kPa (0.9331.227 kgcm2, 13.5317.79 psi)