A theoretical stress analysis was performed on the crankshaft of a 2-cyl engine using routine engineering calculations, and the results were verified by test. Agreement was satisfactory under controlled operating conditions. Actual service loads were found to be about half as high as the maximum possible. The fatigue strength of production crankshafts was measured in a specially built fixture. About 20-30% improvement in fatigue strength could be achieved by shot peening or Tufftride.