Leaky Front Master Cylinder and Need New Final drive fill bolt

[bikerphil]

There are 2 types of OEM, on the early type, the plastic resivour is held to the body by the 4 screws that hold the cap on. The late type has a metal disk in the bottom with 2 screws holding it down.

[Larrym]

Cool. I don't have much to lose... if it fails I will get a whole new unit as planned.

I don't expect the EPDM O-ring itself to fail. (O_o)

AFAIK, it's the same material the actual "rubber" parts (Cups, rings, etc...) in the MC rebuild kits. (Which of course I did just because I had the whole thingy off the bike and on the bench.) (◔_◔)

AND just like one is s'posed to do with all the internal parts in the MC rebuild, I "soaked" the new MC Reservoir O-ring in DOT3 brake fluid to get it pliable and slippery before installing/putting it all back together. (ʘ‿ʘ)

Yur lucky with the Standard Reservoir. It has straight sides and just twists/slides out. (◠﹏◠)

The specials reservoir goes in with a sharp BARB like (45 degree lip) all around the very bottom which made getting the old (weepy) O-ring out a very "Special" project. (⩾﹏⩽)

The old O-ring did NOT survive the process. (_Oo)

[cajun31]

LAB3, Brake fluid is silicon based (should not corrode a Nitrile O-ring) and since the master cylinder is so far away from the hot calipers, there is not much heat to deal with. However, if you can get Viton, that would be the better material. I think Buna/Nitrile would work fine. I use Nitrile in my KZ1000/750 rear master cylinder cups and they have lasted for many years. I have that part reference if anyone needs it.

DOT 3 is not silicon based. It is glycol ether based. Only DOT 5 is silicon based. I am assuming you were talking about DOT 5 in your comment.

[Ccitis]

Just waiting on O rings... so, there is a round o ring under the more square reservoir? I assume mine is the stock reservoir. It is not round.

[DEEBS11]

This is from an XS650 but is similar to an XS1100.

[LAB3]

Cool. I don't have much to lose... if it fails I will get a whole new unit as planned.

The sad thing is you can get a new MC cheaper than a rebuild kit! I've also used the ones similar to what DEEBS linked to and they do indeed work well, can't beat them at that price

[Larrym]

This is from an XS650 but is similar to an XS1100.

Really like this post and ones like it. Thx, DEEBS11! (◠﹏◠)

Photos of what's hidden until one actually takes things apart. Sure, there's a genuine sense of discovery/surprise when you remove something for the first time to look at what's underneath and go, "WUT!??" (⊙_◎)

In this situation, much better to know-before-you-go. (ʘ‿ʘ)

Also this illustrates exactly why I was so confused by my inter-web searches-

"The O-ring is made from Nitrile Rubber and is OIL Resistant"

STILL feeling like a crash test dummy fOaR choosing EPDM. ¿ⓧ_ⓧﮌ

[OldGreyBeast]

Thanks for starting this thread OP! The master cylinder was my next project. I went ahead and got the o ring for the reservoir as I can tell this one used to leak. Have the MC soaking in the ultrasonic cleaner now

[Ccitis]

Ah, those photos make sense. I am just waiting on my O rings. If I can keep the stock one,I will be very happy! This site seems to have all the answers for my old XS. Amazing resource.

[Ccitis]

Really like this post and ones like it. Thx, DEEBS11! (◠﹏◠)

Photos of what's hidden until one actually takes things apart. Sure, there's a genuine sense of discovery/surprise when you remove something for the first time to look at what's underneath and go, "WUT!??" (⊙_◎)

In this situation, much better to know-before-you-go. (ʘ‿ʘ)

Also this illustrates exactly why I was so confused by my inter-web searches-

"The O-ring is made from Nitrile Rubber and is OIL Resistant"

STILL feeling like a crash test dummy fOaR choosing EPDM. ¿ⓧ_ⓧﮌ

I ordered your EPDM one, so there will be two dummys lol. Lots of articles online of EPDM O rings being used in auto brake applications though... including race cars... soooo

[Radioguylogs]

I've had one EPDM in service for 14 years, no problem.

The next EPDM is 9 years with no problem.

There are two younger ones with no problems.

[DiverRay]

Brake fluid is NOT oil based, so EPDM should work with no problems for years. Gasoline and motor oil is what will take out the product.

[DEEBS11]

I'm sure EPDM will work. However, I have had a Nitrile O-ring in my KZ rear master cylinder for several years and it has not deteriorated. This is a bike that actually gets ridden under the worst conditions. It's not a coffee table bike.

[Larrym]

Iffin' you haven't yet pulled off the resevoir and got your own "eyes-on" experience? (O_o)

Mebbe wurth watching.... ¯\_(ツ)_/¯

https://www.youtube.com/watch?v=inA5FRDBTQQ

[DEEBS11]

That 3D print stuff is amazing. It's like the Replicator on the Enterprise.