Sea Foam Rocks!!
Just replaced the diaphragm on a Briggs 9898C which was given to me. The PO said he'd taken it to a local shop and they told him he needed a new carb and he felt that was too much money. He stopped by WalMart and got something else and dropped this off at my barn. It's a 96 and I've never seen a filthier carb, inside or outside. Flushed everything out with Carb Cleaner and reamed out everything I could find with a welders torch tip cleaner. It ran, but was very rough. Let it Sputter for a while, then shut it off and added a couple ounces of seafoam. I thought it was running rough before....:-) I left it running and went in the barn and changed a gas filter on one of the small tractors and did some other odds and ends. As I worked I could hear the Briggs surging and trying to come up to full throttle. It finally did, let it run WOT for a while, shut it off and refilled the gas tank. Started right up, and I mowed around the house with no problem.
Gotta be creative with these "throwaway" carbs...Probably the labor to do what I did in a shop would have been more than a carb?.