I bought a 2003 Honda 300ex the Monday after Thanksgiving. I did a test ride and looked the engine over for any sign of oil/gas leaks. It ran very strong and I didn't find any leaks. The guy that I got it from lived less than a quarter mile from me, so I paid him and took off on my first ride. A couple of days later It started to run rough at full throttle. A few days after that it started to pour oil. I took the gas tank off and gave it the white vinegar treatment to remove rust and any build up. I washed out with water and sodium bicarbonate. Next I filled the tank with ethanol free gas. I shook the tank around and immediately dumped it out. I also cleaned up the petcock and made sure that gas would pass through it. I put the tank back on and fully expected it to run better. It ran after I got back together, but if anything it ran and smoked even worse. It also wouldn't idle. I accidentally let it go dead while trying to shift it into reverse and it wouldn't crank back up. This morning I went throught the whole process to hopefully get it going. It cranked after I shot a little starting fluid to it, but it ran rough and smoked like a loaded freight train. The minute that I let go of the throttle it died again and wouldn't start again. I can't even to begin to look for the oil leak when it won't stay running so right now all I have is a 300+ paperweight. I'm not a mechanic by any means so I was hoping someone here could offer an idea what is going on with it. I've had the thing for a month and only got to ride it 5 hours or so. I'm so disgusted with it that I can't even stand to look at right now. Any advice would be greatly appreciated.