20hp Intek Backfiring with wet plugs

[jaf2h]

I have a Lt200 Snapper with a 20 hp Intek B&S I ran it out of gas the other day, and went and got gas in the only can I had which may have had some two stroke oil residue in it. I started it back up and it was running very choppy and backfiring almost like it was running out of gas. I have replaced the oil plugs fuel filter and drained that gas out and put brand new clean gas out of my usual gas container. The plugs are pitch black after 5 minutes of running and it blows smoke when it backfires. Any help would be appreciated. It was running fine just before this. Ive read that some people use their left over two stroke up in small increments in their lawnmowers so I didnt think it would be a big deal. Any help would be appreciated. Let me know if you need any other information

 

[EngineMan]

If it was only two stroke oil in the fuel, then drop the fuel out of tank and carb again and refuel and try again, it will take a few minutes to clear. and should be no damage to the engine.