Replying to an old subject....Unfortunately the fouling problem is an engineering issue. There is no cure for it.
In a nutshell...it is a 2 cylinder engine with fuel injection...one injector. The engine is obsolete...so Kawasaki isn't going to do any "fixes" for it. Some folks use a hotter spark plug on the fouling side.
If Kawasaki had engineered it with 2 injectors...lifetime engine...they didn't. It is a way over engineered engine in a beast of a tractor...John Deere does that to keep the dealer shop busy.
July, 2020...the injector (rarely fails) is over $300 (if you can find one) and the computer (rarely fails) that reads all the sensors and adjusts everything is over $1200 (if you can find one), ignition switch/control module combination (rust kills it...aftermarket from China) is $150. Anyone would be money ahead to scrap the Kawasaki and all the electronics and install a modern day engine...about $2000 new...then you would have a reliable beast.
I'm currently working on 1996 that has only had the plastic timing gear changed years ago. It has 2300 hours on it. Original injector and computer. Installed new coils and a rust damaged ignition switch/control module. It needs a new seat and $350 power steering cylinder.
Factory 800 page John Deere service manual is available as a free download online. As is a Kawasaki factory service manual.