I'm not a pro, but I've used a Briggs & Stratton manual to adjust the governor on my 6 hp B & S. If it is B & S, I need to know how the governor connects to the engine. Should be one of two different types: 1: Governor arm connects to a shaft that goes into the crankcase. 2: Governor arm connects to a curved vane that operates from the air coming off the flywheel fan. Let me know what you have. If it is not B & S, I will not be able to help.
Have to study it, on my 40 year old Lawnboy, still runs, I increased the speed from 3,600 RPM to 3,800 so it wouldn't stall if the blade encountered a blade of grass. Did this by adding a couple of washers under the governor spring, could have just stretched it, was a guess as the flywheel had to be removed to get at it, and wanted to be able to reverse it if I had to. Now it can hit two blades of grass without stalling, used a phototach to measure the speed.