Brake master cylinder.

[Johnny4428]

To paint or not to paint? I know these were not originally painted, don’t know what type of coating they had, but was thinking of painting in a satin finish, or just leave in it’s faded state. Already fitted new seal kit.

[SumpMagnet]

I went through the same dilemma.

I opted to paint...but the risk then, of course, is getting brake fluid on the paint, as it will likely do a good job of taking it off.

[Bryanj]

Originally anodised

[Johnny4428]

Thanks guys, next question is this being quite a simple brake system will it work with Dot5 silicon based brake fluid, don’t think it has the paint stripping qualities.

[Bryanj]

It will if you have replaced all the seals and cleaned out all the pipework, reservoirs etc.
I have been told that whilst dot5 dont absorb water it does boil at a lower temp, never tried it so cant confirm that

[Johnny4428]

All seals replaced and new brake pipes, so no traces of old fluid within system Bryan.

[K2-K6]

Dot 4 & 5 are compatible so won't give you any realistic problems as seal compatibility exists between them.

Apart from being less corrosive for 5 I understand it as Bryan put,  that it doesn't effectively absorb water.

It's a odd situation though as Dot 4 holds water in suspension,  and so reduces boiling point as %i ncreases. The same water ingress to Dot 5 effectively drops to the lowest point of the system IF it were to get into the system in the same fashion.  This would also reduce effectiveness in a similar fashion.

Characteristic of bike systems though with a "bladder" type seal in master cylinder, they have very very small potential ingress of water to the effectively closed system and so doesn't really have to be considered in a normal service schedule. Nothing really to worry about if all components are to specification and working properly.

Incompatibility generally in brake systems comes from those using mineral oil as the seal specification are different to the Dot type systems.

[Laverda Dave]

Don't bother trying to paint the master cylinder as being anodised the paint won't stick even if you use a primer and it will craze before flaking off. Ask me how I know

[sye]

I painted mine just fine. Use a dremel wire brush to remove the old finish and prime with etch primer. Top coat in satin black, job done.

[Seabeowner]

Dot 5 fluid is more compressible than 4 or 5.1. Don't know how much difference that makes on a small system. Bought some a while back and not tried it. And not that it worries our old machines it is not recommended for ABS as far as I know.

[cbxman]

Thanks guys, next question is this being quite a simple brake system will it work with Dot5 silicon based brake fluid, don’t think it has the paint stripping qualities.

Hi John,

I have had DOT5 in my CBX, front and rear, for 20 years after a full strip and rebuild and have not touched the brakes since.  Japanese bikes tend to be OK with Silicon.  I believe that Italian bikes are not compatible, but that is old information.  Things may have moved on in that regard.

As mentioned before, Just make sure every part and pipe is cleaned and change all the rubber parts together.  No problem.

Cheers,

Jerry

[Yoshi823]

Dot 4 & 5 are compatible so won't give you any realistic problems as seal compatibility exists between them.

Apart from being less corrosive for 5 I understand it as Bryan put,  that it doesn't effectively absorb water.

It's a odd situation though as Dot 4 holds water in suspension,  and so reduces boiling point as %i ncreases. The same water ingress to Dot 5 effectively drops to the lowest point of the system IF it were to get into the system in the same fashion.  This would also reduce effectiveness in a similar fashion.

DoT 4 and 5 are not compatible. It is DoT 5.1 which is.

I used DoT 5 back in the early '80s for my Honda CB750F2 Special & never had any problems. It did need very careful bleeding as tiny air bubbles would compress under braking if not bled successfully.

[K2-K6]

Yep, you're right and I missed the  .1 there 

It's even written on the cap of systems I'm currently working with

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Albeit on mountain bike hydraulic brakes.