Yamaha F25 - Crankcase Assembly

1-17
SPEC
Specification
Crankcase assembly
Item Unit
Model
F25MHA
F25EHA
Cylinder
Bore mm (in) 65.000–65.015 (2.5591–2.5596)
Piston
Diameter mm (in) 64.950–64.965 (2.5571–2.5577)
Measuring point mm (in) 5.0 (0.20)
Piston clearance mm (in) 0.035–0.065 (0.0014–0.0026)
Ring groove (Top) mm (in) 1.210–1.230 (0.0476–0.0484)
Ring groove (2nd) mm (in) 1.510–1.530 (0.0594–0.0602)
Ring groove (Oil) mm (in) 2.520–2.540 (0.0992–0.1000)
Pin boss inside diameter mm (in) 15.974–15.985 (0.6289–0.6293)
Pin outside diameter mm (in) 15.965–15.970 (0.6285–0.6287)
Oversize diameter
1st mm (in) 65.200–65.215 (2.5669–2.5675)
2nd mm (in) 65.450–65.465 (2.5768–2.5774)
Piston ring
End gap measuring point mm (in) 20.0 (0.79)
Top ring
Type Barrel
Dimension height (B) mm (in) 1.170–1.190 (0.0461–0.0469)
Dimension width (T) mm (in) 2.300–2.500 (0.0906–0.0984)
End gap (*1) mm (in) 0.150–0.300 (0.0059–0.0118)
Side clearance mm (in) 0.020–0.060 (0.0008–0.0024)
2nd ring
Type Taper
Dimension height (B) mm (in) 1.470–1.490 (0.0579–0.0587)
Dimension width (T) mm (in) 2.600–2.800 (0.1024–0.1102)
End gap (*1) mm (in) 0.300–0.500 (0.0118–0.0197)
Side clearance mm (in) 0.020–0.060 (0.0008–0.0024)
Oil ring
Dimension height (B) mm (in) 2.360–2.480 (0.0929–0.0976)
Dimension width (T) mm (in) 2.750 (0.1083)
End gap (*1) mm (in) 0.200–0.700 (0.0079–0.0276)
Side clearance mm (in) 0.040–0.180 (0.0016–0.0071)
Connecting rod
Small end inside diameter mm (in) 15.985–15.998 (0.6293–0.6298)
Big end inside diameter mm (in) 36.000–36.024 (1.4173–1.4183)
Big end side clearance mm (in) 0.050–0.220 (0.0020–0.0087)
Crankpin oil clearance mm (in) 0.016–0.040 (0.0006–0.0016)
Crankshaft
Journal diameter mm (in) 42.986–43.000 (1.6924–1.6929)
Crankpin diameter mm (in) 32.993–33.000 (1.2989–1.2992)
Runout mm (in) 0.035 (0.0014)
Crankpin width mm (in) 21.000–21.070 (0.8268–0.8295)
Crankcase
Crankshaft journal oil
clearance
mm (in) 0.012–0.036 (0.0005–0.0014)