Why do B-Series smoke?

Im thinking of buying a 93 Mazda. It smokes really bad when you first crank it. Ive noticed several of these trucks doing this. How do you fix this problem?

valve seals need to be replaced - a not too complex job... rubber gets old, then hard, then oil leaks...

Can also be stuck or worn out piston rings, if you don't plan on a rebuild I would do both dry & wet leakdown and compression checks before buying. If either the leakdown test or compression check show improvement with a squirt of oil in the cylinders then it will probably smoke until you atleast re-ring the pistons.