For everyone having surging problems here is a fix that I do on Chinese engines. Get a extra main jet for the carburetor, take it to a motorcycle shop and have them increase the hole 1 size at a time. Only port until the engine smoothes out and runs under load off choke without surging. You need to get it just right and not run too rich. This worked great on all of my Chinese engines and they start first pull with no surging or warm up time. I did the last one in the shop parking lot on my truck bed, it took two sizes over the factory port.
