occasionally when my raptor is cold,when i pull in the clutch lever then shift into 1st gear it will kill the motor.if i rev it up and shift and keep it reved its ok.when its all warmed up and riding for awhile its ok.what is your guess? the idle setting is good.

 

My 05 raptor 350 does the same thing every so often. And sometime if i leave it in gear when i first crank it in a day or two ILL PULL IN THE CLUTCH crank it up and it trys to take off even when the clutch is in but it only takes just a sec or two to straighten out. I wouldnt worry about it if i was you.

 

I had the same problem with my bike. It came down to the weight of the oil. In the cold the oil got to heavy. Once it was warmed up it was fine. Mind you I was running full synthetic.