Yamaha F150B Service Manual

Also see for F150B: Owner's manual Service manual Owner's manual

2-21TECHFEA Technical features and descriptionOffset crankshaftThe crankshaft centerline is offset by 10.0 mm (0.39 in) from the centerline of the cylinder bore. Theoffset positioning results in the disagreement of crankshaft TDC with piston TDC, and allows the dif-ferent duration of compression stroke from that of combustion stroke. Such difference in compres-sion stroke and combustion stroke makes it possible to cause the earlier expansion and to keep thepiston longer at around TDC after the ignition, leading to more effective use of combustion pressureand improved combustion efficiency.It is also useful to reduce the frictional loss because the piston side force, the force in the thrustingdirection generated on the piston during the combustion stroke, becomes smaller.Crankshaft center line Center line of cylinder boreOffset 10.0 mm (0.39 in)