I've got a command pro 18hp on a scag walk behind that's been working well for a few years, a while back it started to run rich, and then not at all, due to the plug being fowled so quickly. After cleaning the plug the mower runs alright for a few minutes until the plug gets fowled again and it begins to misfire and eventually quit running, here's what I've tried to fix it.... Checked airflow to carb Replaced fuel filter Switched spark plugs Re-gapped spark plug (.020 in.) Cleaned carb. MANY times Installed a carb. kit that included a few gaskets, fuel inlet seat, and fuel inlet needle Adjusted carb. (even at the leanest setting it still runs very rich) Checked that the carb. float does float and isn't broken It's been sitting in the garage for about 1/2 a year now, I just can't figure out what's wrong with it, do I need a whole new carb ($130-150ish)? The carbon on the plug seems to be a dry powdery carbon, not oily. The exhaust also seems strange, it has a chemical smell/fume to it, that seems to burn your nose, maybe the engine's always ran like that though. Anybody got any ideas on what the issue could be or how to fix it?