Front brake master - internal baffle?

[JJ_08]

Hi all -

I just acquired a 2017 FZ07 and was bleeding the front brakes.  I noticed that the bottom of the reservoir does not have the little spring steel baffle or diffuser I'm used to seeing on other bikes.  As a result, when I pump the lever with the reservoir cap off, a little stream of brake fluid sprays up out of the reservoir.  

I was wondering if this is normal, or if my bike is missing the baffle?

 

Here's a picture of the baffle/diffuser thingee I'm talking about (from another bike):

 

Here's what the bottom of my reservoir looks like:

 

[Triple Jim]

I have several other motorcycles, none of which has a baffle, so I guess it's not uncommon for it to be absent.  It's a neat idea though.  I've accidentally squirted fluid a few times.

 

Welcome to the board, JJ!

Edited March 30, 2022 by Triple Jim

[JJ_08]

Thanks for confirming, Jim!  Guess I'll plan on keeping the cap on when I bleed the brakes! 

One interesting note - I've found that the spurting tends to cavitate the fluid.  I've noticed that the stream of fluid spraying up, hitting the cap, and then dripping back down causes the fluid to "foam" a little.  After a session of bleeding, I found a bunch of bubbles on the rubber diaphragm as well as the surface of the fluid.  The problem seems to get especially bad when the fluid is low.

Under certain conditions (for example, low fluid and then braking while the bike is leaned over or handlebars are turned), I could imagine air bubbles getting sucked into the line.  I suspect this may be why some manufacturers include a diffuser in the reservoir.  I also wonder if this is one reason why some FZ owners find that their brakes feel a bit soft/spongey?

As reluctant as I am to modify brake components, I might see if I can fashion a little baffle out of a scrap of stainless or aluminum.

And thanks for the welcome!  I'm excited to join the FZ07 community!

Edited March 30, 2022 by JJ_08

[ElGonzales]

I think KTM once had a problem with air bubbles trapped under such kind of baffler. Of course, they buy brake components on the market like anyone else, but I remember a report of this in a KTM forum. 
Air bubbles naturally go upwards, actually I can't imagine they get sucked down the line and stay there. But you never know ... 

[Triple Jim]

In 44 years of riding I've never had any of that happen, JJ, other than a few bubbles floating on the fluid.  When you're lean over, the fluid mostly leans with you, depending of how much you're hanging off or counter leaning.  But yes, bleeding with the cover on is the usual way with all my vehicles that have hydraulic brakes.

Edited March 30, 2022 by Triple Jim

[shinyribs]

All my dirt bikes have had a baffle. It was a plastic dome with several small holes in it. Like a colander flipped upside down. I always assumed it was to prevent foamy fluid from being able to enter the dome (because surface tension) while being jostled around.

I guess it could be for preventing fluid spurts while bleeding, but I have my doubts that the manufacturers would be so generous as to give us that little tidbit strictly for convenience