The smaller B&S motors have been disposable as long as I remember because you can't rebore the
ally block. From 4 HP, and up, They had a cast iron sleeve that could be rebored. I had a mower with a 4hp cast iron sleeve. The B&S were also the most inherently unreliable small motor we ever had on our property. Today, the electronic ignition has been a big improvement. Points? Remember them? You had to pull the flywheel off to get to them and no self respecting bush mechanic ever invested in a puller!