I have an older Simplicity Sovereign 7016 tractor for mowing my lawn. It has a Briggs and Stratton 16HP engine, with points and a coil. Lately, it will lose power after being run for about a half an hour. If I cut the throttle and shut the PTO off it will stay running, but if it stalls out, it will not start back up again unless I let it sit for a while. When this happens, it is not flooded (I checked the plug). As far as I can tell the engine is not over heating. I belive it is something electrical. The points seem to be ok. Could it be the coil? It seems to run ok until the problem occurs. It starts ok, though it runs a little rough for the first minute or so until it gets going. Air filter is clean, oil was just changed, new plug installed. Gas is fresh. Any ideas or things I can check?