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A connecting rod made of titanium alloy is effective for lower fuel consumption and higher power output comparing to a steel one because the titanium connecting rod enables to reduce the weight of both of reciprocating and rotating parts in an entire engine substantially. But up to now, it has been adopted only to expensive and small-lot production models because a material cost is high, a processing is difficult and a wear on a sliding area should be prevented. In order to adopt the titanium connecting rods into a more types of motorcycles, appropriate materials, processing methods and surface treatment were considered. Hot forging process was applied not only to reduce a machining volume but also to enhance a material strength and stiffness. And the fracture-splitting (FS) method for the big-end of the titanium connecting rod was put into a practical use.

An ultra lightweight valve lifter made from titanium alloy was developed for high performance motorcycles. A beta titanium alloy that was fulfilling not only higher strength but also cold forgeability was selected among several types of titanium alloys. A solution treatment and aging combined with the cold forging made a refinement of the grain size of beta phase. As a result, a tensile strength and an elongation of the alloy were reached to 1170MPa and 10.3% respectively. During the solution treatment, oxygen diffusion (OD) treatment was also performed on the beta titanium alloy. The surface hardness of OD layer was increased up to as high as 600 HV. Subsequently, a diamond like carbon (DLC) layer having a hardness value of around 2500HV was formed on the titanium substrate in order to provide a superior tribological property. In between the DLC layer and the substrate, a sputtered Ti layer was formed as an intermediate adhesive layer.