pw80bikerider

Please help, I recently bought my son his first bike, a 2003 Yamaha PW80. He loves it but all of a sudden we started having problems. It is very hard to start now, I have to drain all the gas out of the carb before I can kick it over. When it does start it won't idle at all. You have to keep the throttle open a little or it will die. The worst part is that it now blows oil out the tail pipe! I mean alot of oil, it will cover a 2 or 3 square feet area behind the bike. Please help don't know what to do and my son really loves going out and riding. Thanks!