Yep, they have changed a bit over time. Most seem to be OHV 4 stroke beasts these days. That said, my lawnmower is *still* a side valve B&S, very much old school, and it is 10 years old at the most, likely less. What's more, it is eminently reliable, never had to do anything at all to the engine beyond bending the governor spring anchor point back to where it needed to be and a few oil changes. I use it all year round so no need to winterise it for the off season and I don't have fuel issues because of that.