Yamaha F2.5A Service Manual

Also see for F25A: Service manual Owner's manual Service manual Owner's manual Owner's manual

Contents

POWR Power unit5-25 69M3E11Checking the cylinder bore1. Measure the cylinder bore (D1 , D2, D3 ,D4 , D5, D 6 ) at measuring points a, b,and c, and in direction d (D1 , D 3, D5 ),which is parallel to the crankshaft, anddirection e (D 2, D 4, D6 ), which is at aright angle to the crankshaft.2. Calculate the taper limit. Replace orrebore the cylinder block if out of specifi-cation.3. Calculate the out-of-round limit. Replaceor rebore the cylinder block if out of spec-ification.Checking the piston clearance1. Calculate the piston clearance using thepiston outside diameter and the cylinderbore specifications. Replace the pistonand piston rings as a set or the cylinderblock or all parts, or rebore the cylinder ifout of specification.Checking the piston rings1. Check the piston ring dimensions of Band T. Replace if out of specification.2. Level the piston ring 1 in the cylinderwith a piston crown.3. Check the piston ring end gap d at thespecified measuring point. Replace if outof specification.Cylinder bore (D1 , D2 , D3 , D4 , D5 , D6 ):54.000–54.015 mm(2.1260–2.1266 in)Taper limit:D1–D 5 (direction d)D2–D 6 (direction e)0.08 mm (0.0031 in)Out-of-round limit:D2–D 1 (measuring point a)D6–D 5 (measuring point c)0.05 mm (0.0020 in)S69J5B70D1D2D3D4D5D6c b a dePiston clearance:0.035–0.065 mm(0.0014–0.0026 in)Piston ring dimensions:Top ring a:B: 0.97–0.99 mm(0.0382–0.0390 in)T: 1.95–2.15 mm(0.0768–0.0846 in)Second ring b:B: 1.17–1.19 mm(0.0461–0.0468 in)T: 2.30–2.50 mm(0.0906–0.0984 in)Oil ring c:B: 1.87–1.95 mm(0.0736–0.0768 in)T: 2.10–2.40 mm(0.0827–0.0945 in)