Motorcycle Repair: my bike cant idle, yamaha xs 400, air filter oil

Question
My Yamaha xs 400 dies unless i keep giving it gas. It wont just sit there and idle. The engine get slower and slower and then dies.  

Answer
Hi Ian.

What maintainence has been done on the bike?  Have you replaced the air filter, oil, oil filter and spark plugs?

What is the idlespeed set at?  Have you changed it since this problem cropped up?

What was the bike acting like before this problem began and what happened that may have affected what it does since the last time it ran well?

Let me know and I can begin to assess the problem.
Good luck and ride safe.
FALCON