Do not blow the Needle valve out with compressed air.
It should have a small Rubber seat in it that will go flying out if you do.You'll never find the little bugger if you blow it out.
Short bursts of Carb cleaner on that part will be fine.
If the emulsion tube looks like the one on the left,you can not re-use it with out modifying it.Once removed the small Idle circuit hole (small hole where the threads are) will not line up with the corresponding hole in the carb.
You can mod it if you need to by cutting a groove (JUST slightly deeper that the threads) with a dremel or Hacksaw The whole way around.Then clean the small hole out with a small burred torch tip cleaning kit.
I've done a few of them with a good sharp hack saw.Just go slow and it will work just fine.
Edited by EricFromPa, November 15, 2015 - 02:42 PM.