Hi just replaced a rear brake switch on a 2006 sportster looked at the brake fluid looked pretty bad so i bled the rear brakes when i go to top of the master cylinder i add it to the max line and as soon as i put that cover on the rubber plunger goes in and brake fluid come spilling out the cover what gives?Thx

 

Sounds like you put too much in. The max line is there for guidance while the bike is in use, with the rubber plunger and lid in place. So only fill so the level comes up to that line after you fit the rubber/lid. Over time that level will reduce, as the brake pads wear, so top up as above.