Where would i buy a crotch rocket type of motorcycle? Or is there a place in kunming to browse motorcycles?

I think the only legal imports for crotch rockets would be Aprilla or BMW, or Buell. There are illegally registered Jap models, but would be hard to find outside of the Chinese biker network.

There is a dealership on Yinghai Lu, just off Dianchi Lu. Head South on Dianchi Lu, turn right onto Yinghai Lu. Bout 300-400m on left is an electric barrier that takes you into the area with the Old House Restaurant. As you go through the gate, keep going straight through the car park. Just past the dry cleaners is a bike shop with Harleys and BMW.

Beware of riding unregistered motorbikes. A work colleague of mine was jailed and then deported for this.
Bigger bikes are not allowed into the city either. Unless you can store a crotch rocket outside of the city limits, you have a problem.

Do a search on GoK for motorbikes. In several of the discussions there is a link to a Chinese bikers website.

P.S. Having ridden crotch rockets for many years overseas, I would not do so in China. The other motorists would have zero awareness/concept of fast bikes.

Back home I rode like a mental twat and lived to tell the tale. I don't think I would live very long at all here.