Oil leaking out exhaust

I have a 22 hp twin cyl. briggs and straton with ohv. while it is running oil comes out of the exhaust. it will run it out of oil in just a little while. I have worked on alot of problems with small engines but never ran into something like this. any ideas where to start looking.

How much does piston rings cost for the mowers

When the piston rings get worn, the oil seeps past them, and into the exhaust manifold through the exhaust pipe. you need to change the piston rings.