John Deere 14PB 5.0 OHV Engine issues

I've got an old John Deere 14PB that has been used for over a decade now. This past year we had to replace the blade clutch on it. I'm not sure if it is related, but around the same time I started having issues with the engine entering these periods of time where it almost sounds like it is running backwards. Sometimes it happens right when the blade is engaged, sometimes it happens when the blade is running and you bog the engine down, other times it just happens with no warning.

Here's a video of it doing these things. Very curious what this might be and how to fix it. Makes for MUCH longer days of cutting the yard as it is not useable while it is doing this, and often times cuts off.

https://www.youtube.com/watch?v=tAUWl-F7Le0&list=UUQQyre21QE4Om12fl4GPTCA&index=1

Your mower is running out of gas. Time to clean the tank and replace the filter and fuel lines. May have to clean the carb too.