FH770D-AS05 throttle hunt and backfire

Good Morning all,
 
I've got an older eXmark Zero Turn mower with a Kawasaki FHD770D-AS05 Kawasaki in it, and no matter what I try it won't stop surging and backfiring. I've taken it to have it worked on because I didn't have time but now with this Corona virus going around I can work on it a bit. I have the carburetor out now and sitting on my table but I really don't know where to look on this thing to clean or adjust, If my carburetor is even my problem. Any help is greatly appreciated.