Hey Mrbones if u wanna change over to dot 5 then u have to replace all rubber hoses and seals, because if u dont the combination of dot 4 and 5 will destroy all the rubber parts. As for the locking up problem it sounds like some kind of master cylinder problem. An easy way to check this is if u know sombody with a raptor and there brakes work fine them ask them if u can borrow there master. Install it on your bike and see if it still does it. If not then you master is messed up if it does it then you have a caliper problem.