How many miles are on the bike? It is not uncommon for Air/oil cooled motors to use some oil. My BMW R1100S never used a drop except on long extended trips I would use a small amount, but other R1100S would use some like you are experiencing.

My Buell also doesn't use any to date, but that motor only has 3000 miles on it. If you have 30,000 miles or more, I would say that using a little oil is not a big deal. Do you get any smoke in your exhaust? Is it possible you are maybe blowing by some in the valves and burning a little, the smoke would be a blue kinda colored smoke if that were the case. Sounds like normal consumption on an older engine.