In Oct 2003, my wife was mowing rocks using
the good tractor. Unfortunately, one rock seemed to
create a disruption to the steady rhythm of the engine.
The disruption started on a blade and carried through to
the crankshaft via a belt. Apparently, one of the two
pistons in the Briggs and Stratton Intek V-Twin was under
the influence of an explosion just above, and had little
ability to adjust to the slight pertubation of the
crankshaft and its heavy flywheel. The mechanical
disagreement was taken out on the connecting rod which
connected the two.