When I bought my 1965 Envoy Epic the seller said it needed a new accelerator pump diaphragm. It would stumble and stall under anything more than the most modest throttle inputs. So I figured it could do with a carburetor overhaul since the car had sat for a long time.
The exterior of the carb was filthy when I pulled it off. An initial hit of carburetor cleaner got it looking reasonably ok. Inside however it looked like someone had already got there first. The gaskets looked new and it was quite clean inside. The accelerator pump diaphragm didn’t look too bad but also didn’t look new. I replaced all the gaskets with new ones anyway and blew out anything that I couldn’t physically see.
I re-installed the Solex back on the engine and … the problem was still there. Ran great but as soon as I gave it some throttle it would sputter and die. Getting going requires a delicate foot on the gas and clutch. I racked my brain and tore down the carb a couple times in the hot sun for a few hours. After going through the arm travel on the accelerator pump arm I noticed a vacuum tube going to the distributor was slowly it down a bit. I flipped the tube from the front to the rear of the arm and it worked great. The permanent solution is a longer tube but for now it is a drivable car.