Volt-Schwibe

I had a lawnmower here that was surging real bad too, it turned out to be a bunch of condensation in the carb, inside the various chambers it has. I had to completely open it, and wash it and let it dry completely. Then when i put it back together, it was perfect.

On the other hand, we have a tractor here that has a governor problem that comes back all the time, so i have to constantly adjust the governor settings, what is perfect one day won't work at all the next day.

So, it could definately be either. Or it could be running lean as suggested. To test this, you'll see that the carb has dual linkage, one is actually connected to the governor, and one is spring loaded off of that one, and connects to the throttle control. With the engine running, carefully grab the rod connected to the governor, and try to hold it perfectly still. If you can get it to run smooth, then it's not a carb problem at all, it's in the governor adjustment.

I've found over the years, it's really hard to do any carb work on these motors with the governor in place, so i usually disconnect them entirely while i'm working on them. Once i have them running like a top, that's when i mess with reconnecting the governor, and setting it is alot simpler when you know the engine is running great. I usually make a little throttle pull handle with a paperclip.