Kawasaki kle 500 one cylinder stops working when driving?

Hi I have a Kawasaki 500 KLE love my bike but for some reason I can`t fathom the left cylinder stops firing, occsionally when I am riding and sometimes when I first star the engine. I find that when I remove the spark plug its soaking wet with fuel and if I change it or clean it the bike then starts. There is a good spark to the plug even its not firing so rules out electrics. I suspect a fuel related problem but dont know what any ideas or has this happened to you and if so what was the answer.
Thanks for any help
Tim