The ornamental design for a frontfender for a four-wheeled motorcycle, as shown and described.
FIG. 1 is a front right perspective view of a front fender for a four-wheeled motorcycle;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken lines showing other portions of a four-wheeled motorcycle are included for the purpose of illustrating environment only and form no part of the claimed design.