burnt

How often do people have to change the brake fluid in the rear bake system? Mine is getting dark awefully fast..

I woke up this morning to go to the dealer to get them to check my brakes and chain. Low and behold the bike will turn over chug like a Harley for a few seconds then shut right off. It will restart everytime but not run. There is a big oil smell from the exhaust after the 3rd time of starting...