again Ollie,
I forgot to answer your question regarding the engine........... Myself ? .... I'd take that Briggs off and replace it with one of the current Briggs 3.5 HP power plants as they are just so smooth and this will most certainly avert the engine deck from fracturing..........yes contrary to popular belief the solid decks also do crack this symptom is not just exclusive to the twin railers. I've seen quite a few that are showing signs of fatigue.
Cheers,
BB.