Motorcycle Repair: Dot 5 Brake Fluid, dot 5 brake fluid, rear brakes

Question
QUESTION: Have 2006 Custom Sportster, brought in for 25,000 service.  Was told I have dot 4 and dot 5 brake fluid in my rear reservoir.  Told needed new caliper, master cylinder, and new brake lines.  Question is, if this was the case how long would it take to affect my brakes and what would happen to the brakes if this was the case.  I believe I could run dot 4 in my rear brakes but the brake fluids could not be mixed, is that correct.  I think I am being sold a bridge in NY.

ANSWER: How did they know you had dot 4 and dot 5 in there?
Mike

---------- FOLLOW-UP ----------

QUESTION: Because they said my brake fluid was a brownish color.  I know you can't mix the two.  I was trying to find out if you mix the two together how long would it take for the brakes to be compromised and if they are compromised what happens i.e., does the brakes just not work, do they go to the "floor boards" or do they just no function at all.

ANSWER: Just because your brake fluid is brownish doesnt mean that Dot 4 is in it. Dot 4 and Dot 5 do on mix, so it would look like tow different fluids in there.
I would flush out the fluid several times and put in Dot 5 and you should be fine
Good luck and happy riding
Mike

---------- FOLLOW-UP ----------

QUESTION: It appears I did not get the correct info from mechanic.  It looks like my bike had dot 5 in the front and dot 4 in the rear brakes.  The service mgr. told me I would have to replace the calipers, master cyclinder and brake lines because I had the wrong brake fluid in my rear brakes.  Nothing was leaking and my understanding is you can use dot 4 in a 2006 Custom Sportster, is that correct.  I don't want to pay for something I don't need.  Again my seals were not leaking and the only thing that needed to be replaced were my rear brake pads but they wanted to replace calipers, master cylinder and brake lines.

Answer
You need to use DOT 5 fluid. The dot 4 didnt hurt anything and you dont need to replace the parts they are talking about. Flush the line out well and replace with DOT 5. The only difference is Dot 4 attracts moisture and DOT 5 doenst. DOT 5 has a higher boiling point than the DOT 4
Good luck and happy riding
Mike