These newer Brigg's & Stratton OHV engines are still pretty new to me, so it's taking me a while to figure out the ins-and-outs.
The key with these engines that replaced the old L-Head/Side valve engines is that they are supposed to run cooler and use less fuel. The fuel use in standard form is in easily better than before, and they seem quieter as well. But they don't rev high enough for my liking. Now, this is in no way restricted to Briggs & Stratton, or even the newer OHV engines.
After running it for a while, I couldn't stand it any longer................
Briggs were cunning in how they hid the governor spring tab on these engines compared to the older designs. But I found it and gave it a little tweak, it's now running nice and strong................
Now, do this at your own risk, preferably once the engine has been run in and had the oil changed. The low running revs of these engines in standard form is designed to meet noise and emission standards, not cutting performance. I probably went a touch too far, but I can easily dial that back. The key thing is that it's cutting much nicer now, powering through rather than bogging down under load.
If you want to do this on your newer B&S 125cc, 140cc, 150cc and 163cc engine, this shows how to do it. You don't need to remove the fuel tank as shown, that was to better show the parts in question -