Outdoor Power Equipment and Small Engines - Kawasaki XP Series 15 HP engine

I have a Husqvarna YTH 1542xp Lawn Tractor, about 9 years old. It has about 126 hours on the Kawasaki XP Series 15 HP engine. When new it ran fine at all speeds. A few years ago the engine developed a surging when at idle. Over time the surging has progressed to moderate engine speeds. It smooths out if I pull the choke out some. It runs ok at high speed.

I removed the air filter to get a look at the carb and linkage. There are no conspicuous adjustments on the carb. The engine runs very poor with the air cleaner off. The air cleaner filter appears clean. I replaced it at 69 hours. At that time the new filter made no difference in the surging.

I store the tractor with Sta-Bil in the fuel.
Is it safe to put a fuel additive in the gas to try cleaning the carb?
I've never replaced the fuel filter because the problem does not occur at high speeds.

Any ideas? Thank you, Peter

Change the filter anyway - it's overdue.

Put Sea Foam in it. You can get that from an auto parts store.

You can try an additive but you will likely need to remove and clean out the carb.