I have been working on an old 1997 Snapper rear engine rider with a Briggs and Stratton 28N707 0173-01 15.5hp engine.
I had been experience a lot of issues with the carburetor including float, valve, gasket, and other various minor issues. I decided I might as well get a new carburetor and just replace the entire thing. So, I got one and installed it no problems. It cranked right up like it was brand new! I went and did about a quarter acre of mowing as a test to make sure all the other repairs I did on the mower were good. No issues. Ran like a champ until today. I cranked her up and the engine was surging, not terrible but definitely was a problem. It puzzled me a bit as I had put new fuel, new fuel filter, and a new carb on the thing but I thought maybe some debris in the fuel line got caught in one of the fuel jets or something. So, I took the carb off and cleaned it thoroughly with a wire and some carb cleaner. Everything was free and open, I thought that was odd - I expected something to be there. So, I put it back on the engine and made sure all the adjustments were set to default 1 1/2 turns. Cranked it up, oh my gosh - it was worse! Now I am a bit worried. I shut off the engine and thought for a bit, did some research - perhaps it is the governor, maybe it slipped or something.
I adjusted the governor back and forth, I can make it go away - the surging, but it is at a ridiculously high RPM at idle and unsafe speeds if I pushed the throttle. At this point I am a little confused at what could be causing this. I did try adjusting the idle speed and fuel jet to see if they made a difference, they did not. I did notice the governor arm was swinging back and forth, which is one of the reasons I thought maybe the governor wasn't aligned correctly.
Here are all the new parts I installed on the engine: Carburetor, governor spring, air filter, fuel filter, spark plug, magneto coil, and starter. I also did an oil change.
Here is a video showing what it sounds like (notice the governor arm): https://youtu.be/Ybms1isfwQA
Anyone have any ideas? Could it be a leaking gasket somewhere that got worse when I opened up the carburetor?
Thanks for the replies!