The only strato saws I've rebuilt are MS441s which I think are considered the "high end" quality in the strato saw class.
Of the 3 I have i haven't noticed any bottom end problems? ,but the carbon buildup is atrocious I mean on par with 40 year old dino burning saws! Runs hot?
These saws were all used commercially and 2 severely worked ,probably more hours than I will ever put on them, bearings, crank,and pins looked good if not great,though maybe the big box store saws are a bad design? But the 441 doesn't seem to have the wear points described here that I've encountered.
A quality mix and muffler mod will hopefully help with future carbon buildup but it's unlikely that I'll ever use them enough to wear them out.