@tatorchip16 the reason that bald engagement thing wont engage full is because there is an adjustment nut in the front part of the mower that regulates it.
I picked up one a year ago last december for $30 from a guy that said his wife wanted it out of the garage because her car need the room worse than the mower. It is in showroom condition for the age. We had to drag it up on my trailer because he thought the rear end was broken. All it was the brake was locked up from rust. I went through and replaced the belts, cleaned everything up and freshened up the paint because it's a 1980's model and needed a refresh. The front tires were dry rotted so I replaced both. All in all, it's a beautiful mower that looks show room. The deck has no rust at all. They do not build mowers like that any more.
i know this is a old video but incase u havent found out on those briggs quantums when they wont prime just double up on the gaskets and it should work