some of the ones put in the reed jets destroyed a few engines at daytona i dont know how many rpms or how many minutes were on the engines.but i do know the wrist pin was yanked out of the pistons must have not been a pretty sight.I heard this from my engine builder Pete Michael.
Wow, at the cost of the damage caused, I would be pulling that jug every time the kart came in off the track, looking for early signs of failure.
Or just not run them...