The ornamental design for, a rearcover for a motorcycle, as shown and described.
FIG. 1 is a first perspective view of a rear cover for a motorcycle, showing our new design;
FIG. 2 is a second perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a right side elevation view thereof; and,
FIG. 7 is a left side elevation view thereof.
The lighter half-tone portions shown illustrate environmental structure for the motorcycle or motorcycle Replica that forms no part of the claimed design.