Harley Davidson motorcycles 1940 to 1947 inclusive O.H.V. engine / side valve engine. Service Manual — page 2

CAUTION: Shifter control must be kept in correct adjustment; otherwise driving dogs on shifter clutches will not fully engage in the different positions and are likely to become damaged from jumping out of engagement under driving load.

When shifter clutches become worn or damaged to the extent of jumping out of engagement under driving load, even though shifter control is correctly adjusted, transmission must be serviced as explained under "Overhauling Transmission and Clutch," Page 126.

Checking and Adjusting Clutch Control