Originally Posted by
elkapitan
What does square stroke mean?
square stroke means the bore and stroke are the same number, in this case 16.42mm bore X 16.42mm stroke (ie 16.42X16.42 or 16.42 squared)
the RB S7s and S9s(also "Worlds" editions), along with a few others were all square stroke.
the newer RBs are all long stroke, 16.22mm bore X 16.80mm stroke