My dad's Sears is acting cranky. It will only run with the choke half closed. I completely disassembled the carb and soaked it in cleaner, so I don't think the jet is clogged. I thought I found a vacuum leak in the intake manifold, but I fixed that, and it still isn't better. This has to be one of the simplest carburetors ever made, but it has me stumped. Any ideas?

There should be a gasket between the bowl and the cover around the intake tube. If this area is not sealed the carb trys to draw air from the bowl not through the intake tube as it should and the engine will not run correctly. Your gasket may have dried up or cracked and fell out.
John

There was no gasket other than the paper gasket around the perimeter of the bowl. It makes sense what you are saying though. I will try to make a gasket tomorrow. This carburettor is so simple, it's frustrating not to be able to get it to work.