Hello, Also coming to this a bit late. Bought a beautiful black classic after riding one 2500km across the Indian Himalayas and instantly fell in love. However I too am having this problem, My bike has a shorter non stock exhaust (sounds fantastic) and was riding fine for about 500 miles until the exact problems that Mance listed started happening on my daily commute in London. For the first 2-3 miles the bike is almost un-ridable, popping, backfiring and setting off every car alarm I drive past but if I stick with it the bike starts to ride beautifully, (smells a little hot though) Mance did you eventually solve this problem without having to turn it off at every traffic light? Also getting tired of having to buy a new spark plug every 2 weeks! Many thanks!