[planeoldguy]

Re: anybody here know about rebuilding small engines? Like B&S 3HP?

You can get oversized pistons for them, but be careful, the overbores tend to run hotter. I will do overbores on snowblowers, but not lawnmowers.

If the rod bearing is wiped out you can get an undersized rod and cap from Briggs and have the crank ground to size. The machine work is fairly cheap, I think I paid $70 for my last cyl overbore and crank grind.

There are many good books available over the net regarding small engine repair and rebuilding.