Hi, I recently recieved a 1974 Yamaha DT250 enduro from a friend of mine. He said it was running when the guy gave it to him 2 years ago. I cleaned it up really good, replaced the battery, cleaned out the carb drained the gas and oil, put new oil and gas in. But I cant get it to start. When I try to start it black oil sprays out of the muffler. What do I do?!?!?