Breaking Brakes

[GRom4232]

Hello, all! Thanks again from the bottom of my heart for knowing so much, and sharing the knowledge with the forum users. I already triple-cleaned my carbs (which tuned out to be a '78-'79 type), and will be rebuilding them completely come the weekend, using the resources found here. You people are magnificent.

This bike is my first, and obviously new to me; I am slowly making it road-worthy. The PO was a jackass. The problem is as follows: I found what I thought to be brake drag on the rear wheel. Seeing this as an excuse to change brake fluid and inspect pads for wear, I popped off the calliper, discovering a number of issues.

1. The rubber seal inside the brake is full of cracks. How crucial is its integrity to brake operation?

2. The brake rotor has a small crack extending from the disc edge to one of the slots; it does not continue past the slot. Is that a serious issue? If yes, may I use a rotor from another bike to replace it? $150 is a lot of money to a starving college kid, and I saw some rotors for newer bikes at $90 or less.

Thanks again for your time!

[Tat2demon]

I dont know about the seal but that crack would scare me. Under hard braking theres a chance it could shatter.

[TopCatGr58]

Hey Grom,

Well, the dragging rear brake probably overheated the rotor and lead to the stress crack. You can use a variety of rotors off of essentially all of the XS11's, but since yours are slotted, you'll possibly want to get the same year type, 80-81 series. Replacing the rotor will also be a good time to inspect the rear wheel hub to final drive splines, clean and regrease, as well as take off the final drive from the swingarm and inspect, clean and regrease it as well since on most of these the Zerk fitting doesn't properly lube the splines!

As for the brake caliper, what you may be seeing is the DUST cover seal, it helps to keep out dust/water and such, otherwise corrosion can form faster. The piston seal is deep inside the caliper housing, you can't see it without taking it apart. But with the history of the dragging caliper, we would highly recommend you do just that to clean it thoroughly, corrosion builds up behind the square O-ring and causes it to squeeze the piston too tightly and so the piston won't retract which causes it to drag. A rebuild kit will provide the O-ring and the outer dust seal, but NOT the small "C" shaped metal ring that holds the seal in place.

T.C.

[natemoen]

The seal is what allows the pressure in the caliper to build. If the seal is cracked or gives way you no longer have breaks. Clean the calipers (all of them) and replace that seal (and any others if needed)

Cracked rotor=bad. Replace it as well. Any of the XS11 and XS650 rotors will swap right in. Earlier rotors wont have the slots in them though, but that is a looks thing really. You can find the rotors on ebay or people here for cheap. Post a wanted add in the parts wanted section.

[BA80]

The seal he's referring to is probably a dust boot because you can't see the seal until the caliper is disassembled.

There are rotors much cheaper than you have stated. Just look around. Fleabay is a pretty good source, or Andreas on here.

Not exactly sure but I believe the rotors for an XJ (Maxim) are the same as the 80-81 XS.

[petejw]

you'll also want to clean and strip the m/c
theres a small hole in the m/c to allow fluid
to return if that hole is blocked it will cause
the brakes to drag.

[DGXSER]

I had the same issue with the rear brake rotor on Banshee when I got it. In my case the PO actually wore the rear brake pads half way through the metal of the pads.

Definitely replace the rotor, but a used one is fine. I have gotten a set (all three) for forty plus shipping before.

As to the caliper, I think the others have you covered, your probably seeing the dust boot. But I would definitely clean up all three calipers and both master cylinders before you go riding much. If you do not do it now, you will be doing it soon, when the brake systems give you fits while riding. Hopefully that will not be when they fail to work for you coming hot into a sharp turn. Then you may not care about the brakes on the bike as much as the ones in your bones.

[conquest87tsi]

Rotor

I definetly would not reinstall a cracked rotor. I actually just removed the rear end and swing arm off of my parts bike last night, which is a '81. I just wanted to do it on the parts bike before I did it to mine. Basically was just removing the rear wheel to I could replace the tire today, but as long as I was there I removed the diff. as Top Cat recommended and cleaned and regreased everything.

Long story short, I have a good rotor from the parts bike. Not sure what i'ts worth I guess.

[WMarshy]

Yep they pretty much got ya covered... when you go to take the rear wheel off take a close look (or picture) of how the spacers go back together on the axle. Welcome to the forum.

[GRom4232]

Good afternoon, gentlemen! Thank you for the advice. I will have a look at the splines today, and re-grease as necessary.

I see a rotor from a Standard 1980 XS11 on sale for $15 on eBay. Will the rotor from the Standard fit my SG? Don't care about the slots at the moment. All I need is something to get me rolling on my way to work.

[natemoen]

Good afternoon, gentlemen! Thank you for the advice. I will have a look at the splines today, and re-grease as necessary.

I see a rotor from a Standard 1980 XS11 on sale for $15 on eBay. Will the rotor from the Standard fit my SG? Don't care about the slots at the moment. All I need is something to get me rolling on my way to work.

All the XS11 and XS650, standard and special rotors will interchange without issues.

There is however a rare oddball rotor that pops up every now and then that seems to be a manufacturing "fix" rotor. It is dished ever so slightly different, bad part is there is no way to tell if it is one of these till you get it. They are rare but just wanted to let you know.

[fredintoon]

All the XS11 and XS650, standard and special rotors will interchange without issues.

There is however a rare oddball rotor that pops up every now and then that seems to be a manufacturing "fix" rotor. It is dished ever so slightly different, bad part is there is no way to tell if it is one of these till you get it. They are rare but just wanted to let you know.

Hi Georgie,
me, I'd open up that crack with a hacksaw cut and soldier on.
there's posh aftermarket disks that are made like that on purpose.
But Nate ain't telling the whole story.
Any XS11 disk will work on your bike.
Post '76 XS650 one-piece front disks will work on your bike.
XS650 rear disks and any disk from an XS750/850 will bolt onto your wheel but they have an unusably smaller diameter.
2-piece disks from a '76 or earlier XS650 will bolt onto your wheel but they have an unusably different dish dimension.
If you have access to a bench drill, cobalt drill bits and lots of cutting fluid
(Yamaha disks are made from really tough material) you can drill a fancy hole pattern in a plain disk to enhance it's performance.

[GRom4232]

So, I tried to remove the brake piston today, and found out that it's bloody difficult. I am unable to push it out with the brake's own hydraulics. I am now seriously considering taking a pair of vice grips to it. How would you normally take out a piston for cleaning?

[natemoen]

Put a regular bolt into the banjo bolt hole, and crack the bleeder bike and put a grease gun on the bleeder and start pumping. She will slide out then. Just clean it out very well after.

[petejw]

So, I tried to remove the brake piston today, and found out that it's bloody difficult. I am unable to push it out with the brake's own hydraulics. I am now seriously considering taking a pair of vice grips to it. How would you normally take out a piston for cleaning?

some pump grease thru the bleeder with a bolt in
the fluid inlet with the caliper off, ive never done it that way
to messy for me,
ive used vise grips if there large enuff and u grab the end
of the piston and work it out, if the piston is seized
grab a hammer and a piece of wood on
the piston and given it a few wacks to break the seal.