Wrist Pin Wear
While wrist pins are usually made of very tough steel, case hardened with the object of wearing out an easily renewable bronze bushing in the upper end of the connecting rod rather than the wrist pin it sometimes happens that these members will be worn so that even the replacement of a new bushing in the connecting rod will not reduce the lost motion and attendant noise due to a loose wrist pin. The only remedy is to fit new wrist pins to the piston. Where the connecting rod is clamped to the wrist pin and that member oscillates in the piston bosses the wear will usually be indicated on bronze bushings which are pressed into the piston bosses. These are easily renewed and after running a reamer through them of the proper size no difficulty should be experienced in replacing either the old or a new wrist pin depending upon the condition of that member. If no bushings are provided, as in alloy pistons, the bosses can sometimes be bored out and thin bushings inserted, though this is not always possible. The alternative is to ream out the bosses and upper end of rod a trifle larger after holes are trued up and fit oversize wrist pins.