The ornamental design for a gripheater for a motorcycle, as shown and described.
FIG. 1 is a front perspective view of a grip heater for a motorcycle showing my new design;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a bottom view thereof;
FIG. 9 is a cross-sectional view taken through line 9-9 of FIG. 5;
FIG. 10 is an enlarged view of the region identified by the broken-line indicia in FIG. 9; and,
FIG. 11 is an enlarged cross-sectional view taken through line 11-11 of FIG. 3.
The even-length broken lines showing of the remainder of the grip heater for a motorcycle represent unclaimed subject matter and form no part of the claimed design. The uneven-length broken lines immediately adjacent to the shaded area shown in FIGS. 9 and 10 represent the bounds of the claimed design and form no part thereof.