caliper rebuild

[DGXSER]

All I will say is this is one heavy A$$ bike for one break to stop. I am sure you won't find anyone tell you it can not be done, but I am certain you will find many who tell you it SHOULD not be done, and you SHOULD be using both brakes on every stop. JMHO

[CatatonicBug]

Thanks a lot c bug. The piston they sell on partsnmore wont work?

Unfortunately, it won't. The size is unique to this model/year and just not carried anymore (this is true for the rear Master cylinder rebuild kit as well). However, you don't need to replace it unless the one you have is mangled. As long as it's still shiny and smooth, the rubber o-ring in the rebuild kit is what rubs on the inside of the caliper bore, so there is no need for a "Perfect" surface. I would say to just rebuild the piston you have, clean it up really well (especially the groove where the rubber ring sits), and see what happens.

Is it a pain to just take the front left caliper off completely? i no it runs off the rear brake so i dont even really use it that much.

NOT a good idea!! The linked brakes of the '81 MNS ARE a pain to maintain sometimes, but it is the same setup that they used on the '82 XJ1100. You need that extra braking power, and should be using the pedal EVERY TIME you slow down. Get in that habbit. It may save your life one day. These are very heavy bikes, and need all the stopping power they can get.

[Str8OuttaHell]

yeah, alright. Well the problem with my piston now is the surface where it touches the brake pad is a little bit ground down. If i just smooth that out should it be fine?

[CatatonicBug]

yeah, alright. Well the problem with my piston now is the surface where it touches the brake pad is a little bit ground down. If i just smooth that out should it be fine?

IMHO, I would think that would be fine. Try your best to get a nice 90 degree surface so the pressure on the pads doesn't cock it sideways in the bore.

[Str8OuttaHell]

ok i will do that then. Can you take a look at this link and tell me if any of these rebuild kits will work? I only need fronts. Thanks Cbug

https://www.z1enterprises.com/catalo...S1100-1981-WB0

[DGXSER]

Perhpa sI am about ot learn something new, I thought the calipers and such on a MNS and those on the Special were the same. I was under the impression that only the linked brake system was different. However, that being the case your still SOL on the piston.

As to the surface of the piston, clean it up the best you can. Like CBug stated keep it fairly even against the pad and you should be fine. Only a short portion of the piston that is inside the caliper will actually contact the O-ring seal. That is th eonly real "seal" on the caliper, the outer rubber is just a dust seal. Definitely pull the o-ring out and clean behind that REALLY good. Most problems with sticking brakes on these bikes that I have experienced or read about are from the crud building up behind that seal, or the "spooge" hole being clogged. HTH

[CatatonicBug]

ok i will do that then. Can you take a look at this link and tell me if any of these rebuild kits will work? I only need fronts. Thanks Cbug

https://www.z1enterprises.com/catalo...S1100-1981-WB0

Yeah! The part number KL32-1602 will work, and it's cheap too! Remember you need 2 sets - one for each side.

DGXSER - I believe you are correct. The front piston for all the specials is made of unobtainium.

[John]

Yeah! The part number KL32-1602 will work, and it's cheap too! Remember you need 2 sets - one for each side.

DGXSER - I believe you are correct. The front piston for all the specials is made of unobtainium.

I had to have 10 sets made a few years ago, and these were made of 404 stainless, not unobtainium. Having just one or two made will be expensive, but by having 20 made the price was about $20 per. Sorry but I sold all of mine.

[Str8OuttaHell]

Thanks a lot guys.

[TopCatGr58]

Hey Str8,

Okay, the 81MNS and the 82XJ use the same front calipers...verified by the Official Yamaha parts fiche site, and they are NOT the same as the 81 Special or the 80 Special, nor any of the standards!!!

Partsnmore.com carries a piston seal kit for the front 81MNS,
it's part #29-0126. Surprisingly, they don't list this same kit for the 82XJ!? But I've found parts listed for the XJ that would work for the XS and they/PNM didn't have it in the XS listing!

That part on Z-1 E looks just like the photo on PNM, but their part #'s are different, but they list the OEM Yamaha Part #. BTW, Z-1 lists the LH as an 82, not an 81.
T.C.

BTW, if you don't like using the rear brake much, you can convert the left front caliper to run off the front MC, a search for linked brakes or unlinking should reveal threads with the info. The front MC is a bit small in capacity, BUT if you fit SS lines then it will work effectively to drive both calipers.

[CatatonicBug]

Thanks for the info TC! It can be tough to find parts for the MNS's sometimes, and knowing where to look makes all the difference. The idea of removing the linked setup from the MNS and making it so the hand brake works both front brakes IS a possibility, but I think I would suggest finding a slightly larger bore front MC first. The '81 MNS has a smaller bore front MC than the other specials because it was not designed to run both brakes.

Same in reverse for the rear MC. The Rear MC on the '81 MNS is 11/16" bore, while the other specials are smaller. They ramped it up even larger on the XJ to 3/4" bore on the rear. The rebuild kits for the Rear, 11/16" MC are definitely unobtainium. I had to replace my MC with one from an XJ, because I was unable to locate a rebuild kit.

[Str8OuttaHell]

hmm.. i just ordered the ones off of z1 i hope they fit... the partnmore are out of stock.

[CatatonicBug]

I'm sure they will. If you have any problems, they are good about making things right too. Unfortunately, they are in Canada, so you have to wait a while for shipping sometimes.

[Str8OuttaHell]

I'm in VT so it might not be too bad. Paid for 3 day shipping too...