I recently got a 1991 trail boss 250 4x4 model w918127. Don't know much about these. I had a couple questions. I noticed there was a plug missing on the very bottom of the crankcase. Where can I find a replacement plug? And what type of oil should I put on there. I put a little gear lube in the top, just to check if that was all together and it ran out right away from that drain. Sorry for the dumb questions and thank you for any help