2003 Yamaha Kodiak 400 4WD

[1970Yamadude]

My '03 Kodiak 400 has a stalling issue.  When it warms up to temperature (about 6-8 minutes)  It sputters out and dies.  Restarts fine with a little throttle.  Once it has re-started then it runs about 30-seconds and dies again.  The longer I let it sit and cool, the longer it takes to die out.  This is after a few other major things were done recently...  New stator; rebuilt carb.  Coils have proven to be OK.  

So, I've tried another carb (off my 2000 Kodiak) and the '03 Kodiak still does exactly the same thing...  Dies after about 6-8 minutes, otherwise runs and idles just fine.   I'm now thinking it could be a stuck starter plunger.  It may be partially sticking which, I think, would cause the stalling issue once it is warm.  I've had the '03 starter plunger in & out of both carbs a few times due to the carb-swapping.  Am I on the right track here?  Is this a common issue and is it adjustable?

[Ajmboy]

I was leaning on a carb issue but since you swapped it out and have the same issue...check your choke, fuel delivery, air box for restriction. When it starts to die out, see if spraying some fuel or starting fluid into the intake keeps it running to see if its actually a fuel issue. If no different, check your spark plug and coil.

[1970Yamadude]

OK... Thanks Ajmboy...  UPDATE - I believe it is an air/fuel mixture issue now.  I checked the starter cable to make sure it was not stuck and it was moving freely.  I checked air box and no restrictions.  Once I had air box cover off and the foam sleeve off the air filter element, the machine stayed running!!  As soon as I placed the cover on the air box, it died.  I tried this many times and the same result.  Mixture screw is at 3 1/2 turns out.  I noticed there is a crankcase vacuum line from the cylinder head to the air box and then another one from the air box to the carb.  Could either of these be the issue?  Thanks for your help...