How do you adjust the idle speed ona banshee?
My friends banshee always go off when it is not
being accelerated due to too low idle speed.

 

Are you sure it's idle speed? or is he loading up the plugs.... most banshees are not too comfortable sitting and idling for a long period...they want to be revved.

If you still have the tors stuff sitting on top of the carb.... Take off your seat...the two idle adjuster screws will be staring you in the face right under the gas tank. Make sure you turn both screws the same amount...then remove your filter and look into the carb intake. Make sure your slides are moving up and down the same amount and at the same time.
If you do not have the tors still installed...then someone probably put idle screws into the side of the carbs...usually denoted with springs to hold the screws from backing out on you.