I recently bought a 2001 Fat Boy. The manual at my local library says I should use DOT5. The reservoir cover says DOT4. Is there any way to check the fluid to see what is currently in there? I know mixing them can cause gelling so I'm hesitant to start flushing with either DOT4 or 5 until I know what's in there. I'm thinking this is a possible misprint in the manual for that year or that the original owner changed the cover to a chrome one from a different year that says DOT4 on it.

 

Prior to the advent of ABS, most HD bikes used DOT 5.... technically it's a better fluid, just doesn't play well with ABS...

My 2001 & 2003 use DOT 5....

The question is... did a prior owner just change the cap, or go through the trouble of flushing the system to switch to DOT 4...!?!?

Get some water, syphon some fluid out of the reservoir, and do this test.....

 

What's on the rear brake reservoir cover?

 

Is it purple? However, after only a year, it changes to a straw color. Go on Harley.com and put your vin in and you can see the owners manual. If still unsure. Flush it and refill with DOT5. And get a proper cover. People do all kinds of stupid stuff in ignorance.

It came with 5. Here is your answer. Click FITMENT

https://www.harley-davidson.com/stor...-12-9990277--1

 

That's exactly what I needed. Thank you.