I have a craftsman lt-1000 with a briggs 31C707-0230-E1. Air filter filled with gas, so I took the plug out, fuel line off the carb, left the oil valve open for a few days. Installed a cheap new carb yesterday along with new filters and fuel line then put everything back together. At first the engine would surge while idling but it's smoothed out a little. It still surges, and throttle up stalls out with some black smoke. There is no noticeable difference between throttle in the center and all the way down (Throttle down worked properly before this). Max throttle stalls the engine and kicks out black smoke.