2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 150Get this manual
CYLINDER AND PISTON
2.Measure: Piston-to-cylinder clearance
Measurement steps: 1st step: Measure the cylinder bore "C" with the cylinder bore gaugeNOTE: Measure cylinder bore "C" by taking sideto-side and front-to-back measurements of the cylinderThen, find the average of the measurementsCylinder bore "C" Maxtaper "T" Out of round "R" 84.50084.510 mm (3.32683.3272 in) 0.05 mm (0.0016 in) 0.01 mm (0.0004 in)
"C"= maximum of D1D6 "T"= maximum of D1, or D2 maximum of D5 or D6 "R"= maximum of D1, D3 or D5 minimum of D2, D4 or D6