Structure of pivot portion of rear swing arm

摘要

A pivot frame is formed as a casting of an aluminum alloy in a substantially U-shaped manner to be open toward a front side. Attaching bosses of a crankcase are placed between a left sidewall and a right sidewall of the pivot frame. Bearing portions of a rear swing arm are coaxially arranged on outer sides of the pivot frame. A pivot bolt is penetrated from one side and is fastened by a nut on the other side. An adjustment collar is interposed between the attaching boss and the right sidewall of the pivot frame. A side of a fixed portion of the adjustment collar is fixed to the right sidewall, and a side of a movable portion of the adjustment collar is pivoted by a tool. The adjustment collar allows the fastening torque of the nut to be constant, thereby preventing deformation from occurring in a fastening operation even when a pivot plate of an aluminum alloy is used.