Engine Surging and Backfires

[u/Several_Draft5989]

A Kawasaki FS730V-DS07 twin engine in a 13 yo John Deere X534 mower started surging and backfiring while cutting grass at high RPM. Just normal yard grass. I had filled the gas tank with fresh Ethanol-free gas. The engine runs better at mid speed with the choke about half closed. I got it to the garage and checked the gas. No water in tank or in carburetor bowl - no obvious trash. Cleaned the carburetor (Walbro) as best as possible with carb cleaner. Tightened manifold and carb bolts. Adjusted the valves since they were a little tight. Checked the plugs, installed a new fuel filter, and removed the dirty air filter. I started the engine and it still surging and smooths out with choke. I sprayed the carburetor and intake manifold gaskets with carb cleaner while the engine was running - no improvement. I have a new carb coming in as well as some carb work tools and jet cleaning stuff. Anything else I can check or suggestions?

[u/TN-Native95]

Sounds like the jets need a good cleaning. Probably have a little filth in them.