The ornamental design for a tread portion of a motorcycle tire, as shown and described.
FIG. 1 is perspective view of a tread portion of a motorcycle tire, it being understood that the tread pattern repeats uniformly throughout the circumference of the tire.
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is an enlarged fragmentary front view thereof; and,
FIG. 7 is a enlarged cross-sectional view thereof.
The portion of the article shown in broken lines is for illustrative purpose only and forms no part of the claimed design.