My brother has an old classic VW Beetle, that is giving us headaches!! The car was running fine, until he changed the generator. After putting everything back together again, the car was not running smooth.
As he had to remove the carburettor and intake manifolds to replace the generator, we thought it had to do something with the carburettor or manifolds. We replaced the packings and checked for air leaks, but still no improvement.
We then thought something could have fallen into the intake, when the manifolds were off, thus we decided to check the compression, but all 4 cylinders had compression. While at it we also reset the valve clearances and replaced the sparkplugs and spark plug leads as they were old. We checked the spark as well and all was in order. We also set the timing and we also checked for blockages in the manifold, which was also clear.
We determined that it was the right side's two cylinders that was not working, as can be seen in the video, removing the spark plug leads of these two cylinders has no effect on the running of the engine!!
Perhaps 
I hope you enjoyed the post and that you have a wonderful day.
▶️ 3Speak