WTB: rear master cylinder for XS1100F

[gtem]

Been having a heck of a time rebuilding my rear master cylinder on my '79F. I suspect I may have scored the bore up too harshly while cleaning Have tried polishing with 1000/1500grit. With a new "All Balls" rebuild kit it's still leaking down to the dust seal and not bleeding well at all. If anyone in the US has a good rebuildable/usable spare, I'd be interested in buying!

[Ranger_xs1100]

gtem,

I have a couple of them on eBay. Still got a lot of parts to get rid of, so, most reasonable offers accepted. Even unreasonable offers considered.

rucksack.grunt on eBay

[gtem]

gtem,

I have a couple of them on eBay. Still got a lot of parts to get rid of, so, most reasonable offers accepted. Even unreasonable offers considered.

rucksack.grunt on eBay

Thanks Bob! I took a closer look at mine closer and finally identified the bit of pitting in the bore that was likely causing me grief. I skimmed some JB weld on and will try to polish it up again and see if I can sort it out. If not I will be making you an offer on one of yours!

[cajun31]

Thanks Bob! I took a closer look at mine closer and finally identified the bit of pitting in the bore that was likely causing me grief. I skimmed some JB weld on and will try to polish it up again and see if I can sort it out. If not I will be making you an offer on one of yours!

All the master cylinders from all years bikes will work. There is only one exception. The 1981 XS1100 LH or Midnight Special is different because they went to the proportioning valve so when you hit the rear brake it also activates the front left caliper. They carried that forward to the 1982 XJ1100s.
This gives you a lot more leeway on searching for a replacement. By the way Bob's are more of a safe bet, knowing how meticulous he is with his projects, then others might be.
Just my two cents here but I would never trust my brakes to JB Weld. On top of that parts are getting scarcer. Your call though.

[bikerphil]

Question, did you bench bleed the M/C before installing, otherwise you could have the problem you are describing. The piston can be pushed in too far disrupting the rubber seals causing a leak from the back side. Also it is impossible to bleed even with a vacuum pump.

[LAB3]

Mine will not bleed with the caliper mounted since that short piece of rubber hose between the hard line and caliper sits higher than the bleeder. Had to disconnect the caliper and raise it up to get it done.

[DEEBS11]

I had this issues also.

[gtem]

Very interesting, yes I did have some issues bleeding as what you guys describe. But the telltale symptom I noticed with the M/C just on the bench was that it would pull vacuum on the dust seal, implying the bottom "rear" seal wasn't sealing well. I'm going to see how this bore polishes up and seals better. That's an interesting comment too that it's possible to push that piston in too far when bench bleeding and contributing to my "vacuum on the dust seal" observation.

[cajun31]

Very interesting, yes I did have some issues bleeding as what you guys describe. But the telltale symptom I noticed with the M/C just on the bench was that it would pull vacuum on the dust seal, implying the bottom "rear" seal wasn't sealing well. I'm going to see how this bore polishes up and seals better. That's an interesting comment too that it's possible to push that piston in too far when bench bleeding and contributing to my "vacuum on the dust seal" observation.

Re read or read if you haven't the repair tips concerning brakes. Sounds like your seal has slipped on the shaft and is not making a good seal. That or like you said previously the bore is too pitted etc.

[DEEBS11]

This is the tool to use to properly hone master cylinders. Clean the bore afterwards with hot soap and water to get rid of the grit. Leftover grit may be your issue with sealing. it's difficult to clean a bore properly after a hone. If it's not done right you will have the type of issues you are experiencing.

https://dealer.klsupply.com/general-...e-320-grit.asp

[DEEBS11]

https://www.ebay.com/itm/29173207409...Bk9SR66To4n9ZA

[Ranger_xs1100]

gtem,
I just sent you a pm,
Bob

[gtem]

Good info on that ball hone tool for future reference Deebs! I ordered one of Bob's MCs that he had listed on ebay, and also finally seem to have my original not leaking and finally bled it correctly. With the new braided lines, the pedal feel is fantastic now!

[Rasputin]

I am seriously wondering about the whole skimming JB Weld thing. Brake fluid is so bad on so many things like paint etc that I wonder how well JB weld will hold up. Myself I do not think I would trust it and if it fails it may not be at the best moment. I would replace it but YMMV

[gtem]

We'll see how it holds up. It's the rear brake and if it starts to leak I'll have plenty of warning. I'm not sweating it!