Rear brake master cylinder

[HxH]

Fitting a replacement Motoworks used rear brake master cylinder, 08 Bmw r1200Gsa, question for gods of knowledge amongst you,
What type of lubrication is normally required to coat the pressure rod into the master cylinder?

 

[HxH]

Its not a trick question, honest.
My choices are:-
1. Axle grease.
2. Silicon grease.
3. Copper slip.
4. Vaseline.
5. Nothing.
Image of pressure rod circled in red, below.

 

[siddo]

Pretty sure it's 5 and lubed by the brake fluid.

 

[mikeyboy]

Red rubber grease,
It’s waterproof and won’t bugger up the bellows
Anything oil based will react and ruin the boot/ bellows

 

[HxH]

Pretty sure it's 5 and lubed by the brake fluid.

Sounds good, I haven't taken it off bike yet, waiting for replacement to get here first, but did take off heel plate to see leaking fluid bubbles coming from pressure rod, rubber grommet area when brake was applied, it has a spongy feel to it which also means air in system.
A repair kit would have been the way to go, but Motorworks don't seem to have any on their web page, only an used master cylinder, £48.00 and delivery, hopefully fully repaired and as good as new.
Stopped watching you tube video's since my last disaster.

 

[HxH]

Red rubber grease,
It’s waterproof and won’t bugger up the bellows
Anything oil based will react and ruin the boot/ bellows

Thank you very much, that makes sense, I was pretty sure a grease had to go on it. But worried about the rubber bellows.
That answers my question, off to Halford's for a wee tube of red rubber grease.

 

[HxH]

Brake master cylinder all fitted, red rubber grease applied to pressure rod, cleaned the reserve out, also fitted a new length of brake hose, removable hose clips.
Bleeding was not easy with the new bought bleed non return applicator, so took it off and did it the old fashioned way, worked a charm.
Motorworks do not sell rear Bmc repair kits for my bike, but they do sell used non-abs and abs ones with a 6 months money back warranty.
Can not praise Motorworks highly enough, fantastic service they provide, good website, and loads of spares for Hexheads.