Red Dot on Master Cylinders

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bikerdds
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Red Dot on Master Cylinders

Post by bikerdds »

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

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Re: Red Dot on Master Cylinders

Post by EMS »

It means: "Never use DOT5" :naughty: :naughty: :lol:

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Re: Red Dot on Master Cylinders

Post by Larry Zimmer »

EMS wrote:It means: "Never use DOT5" :naughty: :naughty: :lol:
:lol: :lol: I'm with you Mike!
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steve murdoch icoa #5322
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Re: Red Dot on Master Cylinders

Post by steve murdoch icoa #5322 »

EMS wrote:It means: "Never use DOT5" :naughty: :naughty: :lol:
You just couldn't help yourself, could you Mike. haha.

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Re: Red Dot on Master Cylinders

Post by EMS »

O.K. Jokes aside. The OP asked a serious question and he should get a serious answer... 8)

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.

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Re: Red Dot on Master Cylinders

Post by daves79x »

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.

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Re: Red Dot on Master Cylinders

Post by EMS »

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.

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Re: Red Dot on Master Cylinders

Post by daves79x »

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

Dave

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Re: Red Dot on Master Cylinders

Post by Larry Zimmer »

Yes, as mike would know, particularly, paint 'dots' such as this are often used as quality 'check approval' symbols in many manufacturing processes.
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Re: Red Dot on Master Cylinders

Post by desertrefugee »

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.
'86 VMax, ‘83 ZN1300-6, ‘78 GL1000, '75 750K

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Re: Red Dot on Master Cylinders

Post by scottish CBX »

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.

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Re: Red Dot on Master Cylinders

Post by zalle »

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?

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