I have searched and Googled until I am more confused than when I started.
I have a 1982 FXWG but the master cylinder has been changed and no marking on it anywhere I can see. I pulled a sample of the fluid out and compared it to DOT 5 which is what I would think it has in it but the color is different. In the picture the fluid from the bike is on the left and it looks yellow(ish)? and the DOT 5 (on the right) I just bought looks purple..I don't want to mix the fluids because I know of what that can cause..anyone have any ideas? I need to rebuild the master cylinder but want to add the right stuff back..thanks in advance and sorry if this is a stupid question, yes there are stupid questions
Larry

 

The dot5 that comes in the bikes is yellow. The dot5
you and I can buy is purple to blue in color.
Take a little of both and mix them in a container.
If one is dot4 then they will not mix. Just do about
a teaspoon full of each.

 

thanks seehogs!
I mixed the two and the fluid turned clear so I threw an 'O' ring in the container and I'll let it sit a while to make sure it doesn't eat the ring or turn to jell but makes sense that you are correct...thanks!

 

no that is not what happens - the brake fluid suspends and does not mix - the area that the two meet the metal corrodes ALLOY / and the steel spring rusts - and it forms grains of debris -- jz

 

All DOT5 is purple when it is new and it changes color to yellowish over time.

 

yep, that's exactly what happens... when I put it new is purple and when it's time to change it I see it's yello

 

I would rebuild the caliper as well if I were doing a master cylinder. Clean the whole thing up real good and squirt a bunch of brake cleaner in the line and let it drip dry. Then you can use DOT 5 and will have worries about what might have been in it.


carl

 

Funny I Am in the exact same boat right now, my rear master cylinder says DOT 5 only. but the front has no markings at all I would hope that the front is the same. but I tend to over analyze things.

 

I learned from this thread that the DOT5 in the bike is yellow and the DOT5 I bought was purple. I didn't know that LOL...
I did mix some and did a little test for a few days just to be safe. It seemed to mix together and never jelled so I went for it

 

Do yourself a favor and remove, flush and refill with clean, fresh brake fluid. Dot 5 is a excellent choice for your scooter as it is not equipped with A.B.S ( DOT 5 doesn't work well in an A.B.S. System ... it can/will foam under the repeated cycles ) Brake fluid is hygroscopic which means that it will absorb moisture from the atmosphere. The moisture is heavier than the brake fluid so it will ( sooner than later ) work it's way into the master and then down through the lines into the calipers. The moisture will cause several problems. It has a lower boiling point so it will evaporate as the brakes create heat. It will also cause corrosion in the bore of the master and calipers. DOT 5 WILL NOT absorb moisture so it is an excellent choice for the scooter that sits in the garage more than it gets ridden too.