Bleeding the brake system - is the reservoir diaphragm important during bleeding?

[MrMogensen]

In Yamaha Factory 2004 manual it states...

A. Fill the brake fluid reservoir to the proper lev- el with the recommended brake fluid.
B. Install the brake fluid reservoir diaphragm.
C. Connect a clear plastic hose tightly to the
bleed screw.
D. Place the other end of the hose into a con- tainer.
E. Slowly apply the brake several times.
F. Fully pull the brake lever or fully press down
the brake pedal and hold it in position.
G. Loosen the bleed screw.
... and so on...

Is it really important to install the reservoir diaphragm (the black rubber thingy) between pouring in new fluid?
Why isn't it just like on a car? I don't have to keep the lid on the container while bleeding brakes on a car...

 

[FinalImpact]

^^ there is good chance that ever toxic, "mean to the paint" brake fluid will squirt out and dribble on your paint. It has been know to do this when the lever(s) are actuated and or returned.

Also, if you bump the bars or front wheel it could spill and then you'd hate yourself.

Also, its wise as the less exposure time the NEW fluid has, the less moisture it can absorb. Hint - do this on LOW Humidity day!!!!

That's what comes to mind.

 

[FIZZER6]

^ Agreed with above. It's definitely not necessary but the procedures in the manual are designed to minimize the chance of problems if the person performing the task is in fact an idiot.

 

[FinalImpact]

On cages or bikes; if you jab on the pedal/lever its the act of moving piston that often spurts fluid out the port in the bottom of the Reservoir. So i suppose there is the risk of "in the eye" too.

 

[MrMogensen]

Haha
Bled the system (with reservoir diaphragm on). It wasn't as annoying as I thought it would be to install/uninstall before/after adding brake fluid to the reservoir.

 

[MrMogensen]

On cages or bikes; if you jab on the pedal/lever its the act of moving piston that often spurts fluid out the port in the bottom of the Reservoir. So i suppose there is the risk of "in the eye" too.

But I always keep my helmet on!