I have an 18 hp briggs and stratton engine. It was not running right. I put in new plugs and I noticed one plug was pretty clean and the other one was black. I had the engine running for a bit then it dies. I felt the plugs and the left plug was cold and the right plug was hot. I do not believe the left plug is working or firing. What could be the problem??

Mike

Hi,
If it is an opposed twin, a plug wire has probably failed. If it is a v-twin, then a coil has failed. I assume here that both sides have compression.
Peace,
Clarke