Bob, with hindsight it always was unlikely that Briggs had made an engine with the crankshaft sticking out well over 6" from the crankcase. It would be too likely to break off when some clown put a load on the end of it.
The people who made that ride-on had some questionable design features (resulting in that aluminium bottom pulley running loose and self-destructing, as well as a very ugly cantilevered load on the engine's crankshaft), but I am reluctant to believe they'd have a heavy cast iron top pulley rotating at 3,000 rpm retained only by a very light press fit, and luck. Even gravity would be working against them. That's why I'm looking so hard for a pin or some equivalent holding the pulley from falling off the shaft. It could retain itself with a heavy press fit, but then they would have broken the engine's crankcase or bent the crankshaft when they pressed it on, and it could never be removed with a puller for engine maintenance.
