Hi Kelsow,
Dot 4 and 5.1 are both non synthethic polyglycol based brake fluids.While dot 4 is suitable in your application the higher spec 5.1,which is thinner and has a higher dry boiling point of approx 510 degrees F, is recommended.
Hey Kelsow,when you wash your bike post ride push your caliper with your hands hard in against the rotor.This pushes the piston back and forces the fluid up into the master cylinder along with any accumulated air.If you let the bike dry this way it will prevent rust from forming between the pads and rotor.It's also a good quick check to see if your slide pin is getting sticky.Check to see that your rotor isn't slightly warped as this will cause your piston to push back slightly while riding giving you a spongy feel.Otherwise,use your brakes less and your throttle more! :lol: