Motorcycle engines have a higher speed than ordinary automotive engines. High engine speed often causes breakage or other mechanical troubles in reciprocating parts. It is important to analyze piston, connecting rod and other parts under actual operation to enable design of high speed motorcycle engines with higher reliability, better performance, and lower fuel consumption.This paper describes measurement techniques for reciprocating parts and measurement stress in the connecting rod. A linkage device which can pick up signals from the reciprocating parts of motorcycle engines has been developed. Measurement of the stress applied to the connecting rod was carried out with this device. With these measurements, we have been able to clarify how the connecting rod moves under high-speed operation.By measuring connecting rod stress in the high-speed range, it has become possible to clarify stress conditions which have been uncertain until now. It has also become clear that stress conditions vary considerably between the thrust side and the anti-thrust side. The occurrence of high-frequency oscillating stress has also been confirmed.