1991 Club car backfiring and running rough

[kraushouse4]

I have a 1991 Club Car with a KF82 motor that was running very slow and rough and had a rod knock, so I swapped the motor with one that I had taken out of my other cart that was running great when removed. The cart is still acting the same even after the swap. I am wondering if it could be the rpm limiter and if so how do I disconnect the ground wire for it? Could it be something with the fuel pump? What else can I check? I switched the carb and generator when I swapped the engines as well. Any help would be greatly appreciated before I drop this cart off the nearest bridge!