I have a 4 OHP Quattro Briggs & Stratton engine on my lawnmower, and it seems to be running rich. (It sort of "gulps" while running, and near the exhaust a black spot develops when the engine is running. ) I was told there should be a fuel adjustment screw near the sparkplug, but I don't see it. Could someone tell me if there is such a screw, and if so, how I can find it.
Thanks,
JD