A motorcycle frame includes hollow left and right frame members that
define a fuel-containing volume. Left-center, right-center, left-rear,
and right-rear engine supports each depend from a corresponding left and
right frame member. Each engine support includes a first portion that is
coupled to the frame member and a second portion that is coupled to the
engine. Each engine support also includes a stress riser defined between
the first and second portions. The stress riser is configured to cause
the first and second portions to separate from one another in response to
application of sufficient force to the engine or second portion. By
causing the first and second portions of the engine mount to separate in
a predetermined way, the frame members and the fuel-containing volume are
left intact.