I'm with Racinstation in regards to the base gasket. I had the exact same issue with my ProXR 800. I would use up to a litre of coolant every ride and never had a drop anywhere else. Check your plugs, mine was bad enough to show signs on the plug that one was burning fine and the other was washed clean from the coolant being burned. If you leak coolant anywhere, chances are the chasis is going to leave a drop or two for you to find wether in the belly pan or next to the leak source. Mine got worse on more WOT senarios and would burn more than if I was just trail riding taking it easy. Once I replaced the base gaskets and sealed them up good with some Loctite gasket maker my problems were solved. The plugs were the indicating factor even though it sounds like your burning a 1/3 less coolant than I was. I ended up riding around with a drink for me and the sled every trip until I replaced the base gaskets. When I took my cyl heads off the mag side cyl was spotless with no carbon signs and the PTO was normal. If your cyl and plugs are too clean to be true on either or both cyl, you know your burning coolant. Methanol injection baby! LOL