yeah you got a leak somewhere and the stratus tubes I`ll bet are dirty also the seal between the radiator and the cooler box may not be stuck or not sealed good put a led flashlight behind it and have a buddy see if he can see light around the seam on the other side I have seen that leak. the brushes do get hard and fray for me it has been mostly from fructose flying from chopper heads in early fall (now)
Check the aspirator tube on the exhaust, occasionally there is a muffler were the venturi tube is not welded in 100% correctly. Pull the hose off of both air cleaners on both machines and compare the suction. If thats the problem you will need a new muffler and make sure you clean the strato tube pre-cleaner out, they will be plugged due to low aspirator suction.