The International CBX Owners Association

Can someone explain the meaning or purpose of the red dot on front and rear master cylinders? Thanks, Marty

It means: "Never use DOT5"

EMS wrote:It means: "Never use DOT5"

I'm with you Mike!

EMS wrote:It means: "Never use DOT5"

You just couldn't help yourself, could you Mike. haha.

O.K. Jokes aside. The OP asked a serious question and he should get a serious answer...

These color dots are used by the vehicle manufacturer and sometimes by a component supplier to verify that a unit has been checked for correct function and performance.
This happens especially with safety-related components. Even fasteners that are critical for safety during operation are sometimes marked after they have been correctly torqued.
On any motorcycle you will see yellow or red color dots on a variety of parts.

That said Mike - Honda painted a big red splash on the bare master cylinder, then taped off a 'dot', then painted the remainder black. It had to be done during production of the master cylinder, long before it was installed on a bike. Every master cylinder I've stripped to re-paint that had the red dot really had a red 'splash' underneath. Your explanation makes as much sense as anything I can imagine though.

Dave

It was likely not Honda who painted the master cylinder, but the supplier. Function test would have been done before paint, just so the brake fluid would not mar the fresh paint by any chance.

Yes, you are certainly correct - the vendor of the master cylinders made them to Honda specs.

Dave

Yes, as mike would know, particularly, paint 'dots' such as this are often used as quality 'check approval' symbols in many manufacturing processes.

Uh oh. Now the restoration purists will need to duplicate the "splash" under the black caliper paint to be completely correct. Sort of like recreating firewall scribblings on early Detroit iron...

Heck, I thought the dot was a sticker. Shows how much attention I paid to it.

I wonder if the red dot was to indicte that the master cylinder or caliper had been inspected - so they painted a red splash on an area of the part, then used a sticky dot of about 11mm in diameter and then the whole thing was painted (or coated) in black. Once the part was inspected the sticky dot was removed to indicate it had passed trhough an inspection phase in the factory.

I used the same process to refurb my own rear master cylinder a few days ago and it works well, you are left with a very similar red dot which I then covered with satin clear coat. My wife has a Cricut which we use to make all sorts of stensils or signs etc and it came in handy for this.

scottish CBX wrote: ↑

Sun Jan 22, 2023 6:39 am

...
I used the same process to refurb my own rear master cylinder a few days ago and it works well, you are left with a very similar red dot which I then covered with satin clear coat. My wife has a Cricut which we use to make all sorts of stensils or signs etc and it came in handy for this.

Does the clear coat crack in time?