Diasil Cylinder: The DiASil Cylinder was born from YAMAHA’s world-class aluminum die-casting technology. DiASil Cylinders are all aluminum cylinders made by YAMAHA’s proprietary aluminum die-casting technology. An aluminum alloy with 20% silicon content is used to create a very hard, reliable cylinder surface, making conventional iron sleeves obsolete. As a result, the entire cylinder can be made of aluminum, a better conductor of heat, which means the cylinder delivers better heat dissipation and less weight. (Aluminum’s heat conductivity is 3.1 times that of iron.) YZF-R15 is equipped with this all-aluminum cylinder called the DiASil Cylinder and a forged piston, the same type of piston used in YAMAHA’s supersport bikes. FORGED PISTON: The forged pistons made with Yamaha "controlled forging technology" have excellent strength characteristics that enable the design of a thinner, lighter piston with smaller reciprocating mass achieve higher rpm and performance as well as ...