Last summer I did routine maintenance on my 70 bug. I haven't driven it much since then but I noticed that it was tending to die when revving down to idle speed at stops unless I gave it a bit of gas. I finally decided to fix the problem so I went through the various things - dwell, timing, etc. They all seemed good. I took the carb off and cleaned it. There was some gunk inside the float reservoir but the jets seemed clear now. This carb was a replacement Solex I bought 12 years ago when the screws holding the auto choke on the original one stripped out. This was the first time I'd cleaned it in all that time, although I haven't put many miles on the car in that time - maybe 25K. Anyhow, I cleaned it up and put it back on but I couldn't get the car to start at all.
Then I noticed I was out of gas. D'oh! A couple gallons of gas and some final adjustment of the idle and bypass screws and it seems to be running fine again.