We claim the ornamental design for a motor generator, as shown and described.
FIG. 1 is a front isometric view of a motor generator showing our new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left elevation view thereof;
FIG. 5 is a right elevation view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a rear isometric view thereof.
The broken lines shown represent unclaimed subject matter and form no part of the claimed design. The dash-dot broken lines show the boundaries between claimed and unclaimed portions of the design and form no part of the claim.