2 cycle oil draining into exhaust

[Macswinford]

My project 2002 Kymco People 50 2T is draining the contents of the 2 cycle oil tank into the muffler. I poured out a pint of oil from the exhaust pipe. What is the problem and how do I fix it?  Thanks, Mac

[Scootsuper9]

Failed check valve - replace oil pump or bypass and use premix