We have seen a couple of pumps fail and cause excessive oil consumption. If everything else checks out then I would put a different pump on it.
I just completed a 2000 that had a similar problem but his lever was bent over against the pump and jammed wide open due to both front motor mounts being broken. Check yours while you are at it.
Could it be leaking? One of my RMK's had a leaky rubber grommet at the bottom of the oil resevior/tank where the oil line attaches. It was a very slow leak but I would go through probably a half tank of oil every ride. I replaced the grommet and problem solved. Now I get at least 4 rides for a half tank of oil before I need to top it off.
