I had about the same thing with an R50. I eneded up taking it to the dealers shop, they pulled the rotor and gear box off and found a "plug" that covers a hole to tear apart the gear box was leaking. It leaked down the inside of the rotor cage, all the trash in there kept it cleaned off and could no see the leak. I was putting oil in every day. It must have worked, I do not add oil anymore. Hope this helps.