4.5 briggs lawnmower runs too slow to mow

[digger350]

i have a 4.5 briggs lawnmower not all that old and hardly used much it wont speed up enough to mow with its one of those throttle free types i,ve put a new sparkplug in put a new diapham on the carb and even swapped out the gastank and carb for another of the same type and still the same thing it will run but not speed up if you try to mow it will die because its running too slow i,ve worked on briggs motors for years but have never seen anything like this i cant think of anything else it could be any ideas

[K-B]

The RPM limiter probably got bumped (happens all the time on certain models). It's a small bendable arm with a spring attached. You'll need to adjust it to get the RPM's back up, set it to 3200-3500 RPM.