I've been trying to determine which brake fluid is in a 2nd hand bike. I know Dot 5 starts out purple, and Dot 3 is amber/yellowish,but the front is more of clear yellow/tan combination, and the rear is more amber.

Front....I extracted some fluid from the master cylinder and mixed it with some Dot 5 in a clear container. Mixed completely, sat for a while and still no separation of the fluid. Took another sample and mixed it with some water. Fluid looked like oil and vinegar separated in a salad dressing. Two complete layers of fluid. I would assume that the front has Dot 5.

Rear..... Extracted some fluid from the rear master, mixed with Dot 5 in a clear container, globulets formed, and a clear separation occurred after a while, light yellow on top, and purple on the bottom. Took another sample, and mixed with some water and they appeared to mix together with no layer separation. I would assume this is Dot 3 or Dot 4.

Strange as it may seem...front appears to have Dot 5,..... and Dot 3 or 4 in the rear.

Are these assumptions correct?

 

know of no motorcycle that is so rare that the specs can't be determined on-line, from a dealer who sells it, or if it's a harley, right hear on the forum.

What are you trying to prove?

 

If it's used....you don't know what's in it. The MOCO flipped-flopped from 4 to 5 and from 5 to 4 among model years. The lid should specify what goes in there and it may say 4 or 5....but not 3 and maybe nothing at all if it's old enough, or someone has put a custom lid on. You can't be sure the lid has not been changed for some reason if you are not the original owner. Nor can you be sure if anyone has switched from 5 to 4 or vice-versa.

I understand what you are trying to do. Glycol based fluids like 3,4 and 5.1 will mix with water, but silicone based 5 won't. I would say you have 5 in the front and 4 in the rear...as you concluded. 4 is an improved version of 3, so use 4.