Small Engine Troubleshooting Problems? Ask a Mechanic Now.
I do believe that the surging is caused by either a partially clogged jet or fuel passage inside your carburetor.
Did you soak your carburetor, prior to cleaning it?
First, check to see if you are getting a steady, and continuous flow of fuel from your fuel tank, to your carburetor. If you are, then it is very likely that our problem is caused by your carburetor.
I would soak your carburetor really good, and use a small wire to clean the small jets and fuel passages. Then use some carburetor cleaner in can, to clean every hole you see in your carburetor, followed by some compressed air, if you have an air compressor.
We can continue from here. Thanks!