Motorcycles, Snowmobiles, Go-Carts, ATV's and Golf Carts - Help with Briggs 8hp engine

Hello. I have an 8 HP Briggs motor that was originally on a wood chipper. It sat for some time before I bought it. I filled with new oil, gas, etc. Everything maintenance wise was checked on the list. It actaully started and ran the first time as well which was surprising. I am putting this engine on a gocart. I recently put a new carb kit in it as I was having difficulty getting it to rev up quickly, then idle back down without stalling out and backfiring. I pulled the sparkplug several times to find it blacked, so I figure I am running to rich. I have followed the instructions exactly for adjusting the new carb. The engine seems to run fine on a fast idle, and runs fairly smooth on slow idle, but more smoothly when it's cold. Once it warms up, it tends to speed up and slow down on it's own (almost like a stuck float valve, but I checked it and it's clean, and new). I also get a lot of backfiring when idleing down from fast idle. The engine will usually sputter and die as well. Any suggestions? Would this have anything to do with something electrical like a coil? I am also wondering if the puffs of white smoke I get when reving the engine up are related to the engine running too rich, or a bad intake valve? It doesn't smell like oil so I don't think it's burning oil. Aircleaner is clean, choke is working well.

Jeff

is it still governed?