Yamaha 20C Service Manual

Also see for 20C: Owner's manual Owner's manual

Contents

E2-3MAINTENANCE SPECIFICATIONSSPECC31000-0*MAINTENANCE SPECIFICATIONSPOWER UNITItem Unit Model20CMHPower unitCompression pressure (*1) kPa 834 (8.34, 120.9)(Reference) (kgf/cm 2 , psi)Cylinder headWarpage limit mm (in) 0.10 (0.0039)(lines indicate straightedgeposition)CylinderBore size mm (in) 67.000–67.020 (2.6378–2.6386)Wear limit mm (in) 67.1 (2.64)Taper limit mm (in) 0.08 (0.0032)Out-of-round limit mm (in) 0.05 (0.0020)PistonPiston diameter (D) mm (in) 66.955–66.980 (2.6360–2.6370)Measuring point (H) mm (in) 10.0 (0.39)Piston-to-cylinder clearance mm (in) 0.040–0.045 (0.0016–0.0018)Piston pin boss bore mm (in) 18.004–18.015 (0.7088–0.7093)Piston pinOutside diameter mm (in) 17.995–18.000 (0.7085–0.7087)Piston ringsTop ringDimension B mm (in) 1.97–1.99 (0.0776–0.0783)Dimension T mm (in) 2.90–3.10 (0.1142–0.1220)End gap mm (in) 0.30–0.50 (0.0118–0.0197)Side clearance mm (in) 0.02–0.06 (0.0008–0.0024)2nd ringDimension B mm (in) 1.97–1.99 (0.0776–0.0783)Dimension T mm (in) 2.90–3.10 (0.1142–0.1220)End gap mm (in) 0.30–0.50 (0.0118–0.0197)Side clearance mm (in) 0.03–0.07 (0.0012–0.0028)Reed valveValve stopper height mm (in) 5.00–5.50 (0.20–0.22)Valve vending limit mm (in) 0.200 (0.0079)Connecting rodSmall end inside diameter mm (in) 22.004–22.017 (0.8663–0.8668)Big end inside diameter mm (in) 29.004–29.017 (1.1419–1.1424)(*1) Measuring conditions:Ambient temperature 20°C (68°F), wide open throttle, with spark plugs removed from all cylinders.The figures are for reference only.