WR250F fuel mixture

We have a 2006 Yamaha WR250 four stroke. We usually like to ride in the mountains throughout Pennsylvania and West Virginia. Occasionally we'll take the bikes to some near bye tracks. My problem is when I have the choke on while riding the bike It runs great, but after you turn the choke off even after it has thoroughly warmed up the throttle response is awe full and it sputters a lot. It takes a while for it to get up to speed and when you slow down it near cuts off. I believe that the problem is the mixture is off on the bike. How can this be fixed. Or should I say how do you adjust the carborator so the mixture is just right.

Choke on

Bike runs great

great throttle response

basically runs perfectly

Choke off

can't idle for more then 10 seconds

almost no throttle response

nearly cuts off when you slow down below 10 mph

the results of the bike are the same whether the bike has been warmed up or not

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