The ornamental design for, an airintake for a motorcycle, as shown and described.
FIG. 1 is a front elevational view of an air intake for a motorcycle showing our new design;
FIG. 2 is a perspective view thereof;
FIG. 3 is an enlarged front elevational view thereof;
FIG. 4 is an enlarged left side elevational view thereof; and,
FIG. 5 is an enlarged perspective view thereof.
The rear elevational view is a mirror image of the front elevational view, and the broken lines illustrate portions of the motorcycle that form no part of the claimed design.