I picked up a new to me ZRT 600 at the end of this winter and today I was cleaning up. I puled the lid off the airbox to install a power breather and all there was inside was three holes feeding the carbs. Is this normal or did the previous owner gut the airbox? If so what jets should I run with the power breather and airbox the way it is. Thanks for any help.

See whats in there , I'd start with 360's and if a little rich go back with 350's.

I did look in there. That's the problem I don't know what should or shouldn't be in there?

after you take the top off, 3 screws if I remember right there is a shelf there with 3 long tubes with a curve pointed towards the carbs, remove the shelf and the tubes and put your power breather on. An alturnative to the power breather is to remove the shelf and tubes and drill 2.5" holes thru the back of the air box.