Hi Major, I can recommend Michelin City Grips which I found excellent on both my Piaggio X7 and now on my GTS. On the X7 (14" rear if I remember rightly) I could get maybe 14000 km and they work well in the wet and in the dirt. Not sure though if they come in Burger 400 sizes. Gavin
Honda Spacy - 54,000 kms
Vespa 150 Super (for restoration)
Daelim S1 - 640 kms
Piaggio X7 - 27,000 kms
Vespa GTS 300 - see how this goes