I have a bone stock DR650ES doing exactly the same thing. It started suddenly about 2 months ago. When I parked the bike all was normal. When I started it a week later, it would not start with any choke at all. After a week of that, I pulled the carb and removed the float bowl. Lying in the bowl, loose, was what appeared to be a small fixed jet - a brass cylinder about 5mm long and 3mm in diameter, tapered at one end, with a bore of just under 1mm. I took it to the local dealer and they could not identify the part and said the carb was otherwise normal. They cleaned the carb ($72!!!) and gave it back. I put it back on - no change. I did check the choke/enrichener mechanism, which moves normally. I posted this problem on the DR650 board and no one had a clue. Anyone here?