NEW Rear Master Cylinder?

[Peanutbutter Nma]

Hey yall, just hoping someone can point me in the right direction. I bought new components for the whole brake system: 3 caliper rebuild kits, SS lines F/R, new MCs for front and rear, calipers, rotors... All the stuff. The only two parts I was unsure about were the MCs from MikesXS, but my front MC was toast. Pitting in the cylinders and stuff. Rear works, but is slow to return.

I got home, pulled the front MC off the bars and the brake switch cable ends are different than I need, not representative of the picture on their site. Fine, a little annoying, but I can crimp new connectors. Imagine my frustration upon finding the rear MC is a totally different design. In buying a bunch of stuff, I didn't make note of the Universal Fit. I worry about the old rear MC binding up on the road, but I'd buy a rebuild kit if I could find one!

I'm already drafting up drawings to fab some brackets in case I can't return the rear MC. In the event I do send it back, does anyone have a line on reliable replacement rear MCs that are mostly plug and play?

[DEEBS11]

No new MC available that will bolt in. Here is a rebuild kit for the unit.

https://www.ebay.com/itm/29655616108...Bk9SR9SBiPCjZA

[DEEBS11]

A decent looking used unit. Would probably need rebuilding as well. If yours is rusted solid, you may need to start with something like this.

https://www.ebay.com/itm/40513632850...Bk9SR9KBiPCjZA

[LAB3]

I've had decent luck using units similar to this on other bikes, you'd need to swap out the brake line and go with a single hose from the MC back on the XS11.

https://www.ebay.com/itm/155719249155

[DEEBS11]

LAB3, do you think that Chinese unit is safe for a large bike?

[Peanutbutter Nma]

Hey Deebs,

While this first year or so is planned to mostly restore it to something like stock, I plan on holding onto this bike for a pretty long time. That being said I want modern, reliable, easily serviceable components while retaining the character of the bike. I still feel weird about rebuilding untested potential 50 year old parts, am I being overly cautious?

Thanks for the line on the rebuild kit for the rear though, I snatched it up since the rear brake was working when I got it. I don't like not being able to see the level but I'll make do. I'll try to make the other MC work when I find the time for it, could be a fun little project.

The front MC was rusted solid, and too boogered up to use without boring it out or something. I'm gonna hunt around the shop to see if I've got some spare crimp-on connectors that will work. If it comes down to it, I'll just put new connectors on both ends of the wires.

Calipers are all blasted and painted, waiting on the rotors and the rebuild kit and I should have everything I need to check brakes off the list.

[Peanutbutter Nma]

Lab3, that'd probably work but it's not altogether disimilar to what I've got in hand already. Also seems too good to be true. You can barely get that much raw aluminum for that price.

[LAB3]

LAB3, do you think that Chinese unit is safe for a large bike?

As mentioned, a similar unit. During the early part of the COVID freakout I rehabbed an 82 Goldwing and used a generic rear like that one but I did make sure to get one of a similar bore size to the original.

The cheap front MC's that we've both touted on here are probably cheap Chinese units as well.

[DEEBS11]

That is correct, they are also Chinese. Point taken.

[Peanutbutter Nma]

That is correct, they are also Chinese. Point taken.

There is a substantive difference between the chinesium stuff made out of soda cans and the stuff they reverse engineered or stole the prints for. All manufacturing is overseas now, discernment is the name of the game. Price point is usually the first clue.

Just gutted the old rear on the workbench. Seems alright, just gonna send it with the rebuild kit. Thanks yall.

[DEEBS11]

[Peanutbutter Nma]

That bolt on the bottom left is blocking off the port going to the forward brakes, correct? Proportioning valve?

[DEEBS11]

It's just an orifice plug. You can remove that to get inside to clean. Two tiny holes that lead to the cup reservoir need to be clean and free from debris.