Motorcycle brake fluid rapidly changes color.

[THE_TROTS]

I have an issue with brake fluid degrading rapidly.

1982 Kawasaki KZ550.

This bike has a single front caliper, floating style. I have replaced the master cylinder with a new unit, and replaced the rubber brake line with a SS braided line.

I flush the brake fluid at least once a year. The brake fluid has been flushed 4 or 5 times since I have owned the bike (the brake fluid was black when I bought it.) The only original part of the brake system is the caliper. I have no performance issues with the brake. The brake lever is firm (not as firm as a new bike, but I assume brake systems have improved in 30 years) and I can lock the front wheel at will. I have no issues with brake fade, but I don't ride this bike very hard. It rarely sees more than 5,000 RPM.

The brake fluid turns dark much faster than the fluid in any car I have ever owned. Correct me if I am wrong, but dark fluid is because of contamination. I have always used auto parts store DOT3. Is my cheap brake fluid the problem or is it time to find a rebuild kit for the caliper?

 

[slacktide_bitog]

Don't motorcycle brakes get much hotter than car brakes?

You should consider using DOT 4 or DOT 5.1 (non-silicone, not to be confused with DOT 5 silicone)

 

[philipp10]

Rebuild your caliper, probably the seals are releasing materials that change the color. BTW, as far as color change, if it is just color, I don't see what the big deal is.

 

[Oro_O]

I had a an '82 KZ 550 I used for commuting when I was in med school. Reliable though uninspiring bike. I went through it all top to bottom over two years.

I was going to post the same thing as philill10; it's the caliper dirtying it from touching the seals. If it's not leaking, it's not an issue. If you really want to replace or rebuild the caliper, go for it but it's not a big deal.

I was in Seattle where the constant wet 6 months of the year ( and I rode every day in it) made me vigilant on maintenance. it was just a factor and like he said, not a big deal.

While I don't own it any more, I did find an old pic and blurb I did on that bike a few years ago on Bikepics (Just in case you are super-bored):

https://www.bikepics.com/members/kamerer/82kz550/

 

[THE_TROTS]

It is not leaking at all. I will continue to flush it regularly until it does.

I did check out your site as I am always interested in seeing anyone's old motorcycle, especially if they have not destroyed it by cutting it up and turning it into a bobber.

I have not had as much luck as you did. I have had near continuous electrical problems as long as I have purchased it however I have always managed to find the parts to fix the problem.

I agree they are not sport bikes but it is a [censored] of a lot more fun than my 3 speed, 110hp Sunfire. Puts a smile on my face every day.