BMW K bikes (Bricks)

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blaKey

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</A></A></A>Well, my front master cylinder was leaking so I pulled it apart. The bore was too scored so I bought a resleeved cylinder and installed a new piston assembly.

Mmmm...two bits left over: metal washer and a round donut-shaped thingo (see arrows)

The photo below shows arrows pointing to my leftover bits...

Front master cylinder rebuild...still leaking! Frontmastercylrebuildbits


Below is a photo of a brand new master cylinder that shows my leftover bits:

Front master cylinder rebuild...still leaking! Newfrontmastercyl

But when I first took off the master cylinder, those bits were not there. I can only assume that
the previous owner left them out?

Can you please tell me where they are suppose to fit?



Last edited by blakey on Mon Feb 01, 2010 8:24 am; edited 1 time in total (Reason for editing : Amending text.)


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Neil
K100RS 1986 RED!

Dress for the ride and the potential slide.
    

Crazy Frog

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Here is a picture of the rebuilt kit from Magura.

I believe the washer and the seal are just a dust protector. The seal is there to protect from dust entering and scoring the bore. If it wasn't on your original one, this may be why it got scored.

Front master cylinder rebuild...still leaking! Yhst-15102260216258_2091_68959972


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Front master cylinder rebuild...still leaking! Frog15Front master cylinder rebuild...still leaking! Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

blaKey

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Thanks Bert.
All of the manuals and fische show the washer and seal.
I'll pull it apart this weekend and have another go at it.


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Neil
K100RS 1986 RED!

Dress for the ride and the potential slide.
    

K-BIKE

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Be really gentle and don't use any tools to wedge seals in to the bore they cut amazingly easily.
Regards,
K-BIKE

    

blaKey

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Now that you mentioned it K-BIKE, I do remember having a "mmmmm" moment when pushing in the new piston assembly...and yes, there was brake fluid coating the bore and the piston.

Hamfisted is a word that springs to mind!

Thanks guys.


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Neil
K100RS 1986 RED!

Dress for the ride and the potential slide.
    

Ned

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@blakey wrote:</A></A></A>Well, my front master cylinder was leaking so I pulled it apart. The bore was too scored so I bought a resleeved cylinder and installed a new piston assembly.

.....

Hi Neil,

Where did you get the resleeved cylinder? Also, do you have to get the kit just to get a seal?

    

blaKey

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Hi Ned, I got the resleeved cylinder from The BM Shop up here in Brisbane. Send them $120 plus your old master cylinder and they'll send you back a resleeved one.
I think the leak problem is the hole for the reservoir (where's the bloody spellcheck?). It's appears to be a little bit too corroded and there is a small leak. Yes, a new O ring was fitted.

The rebuild kit consists of the plunger for the master cylinder only (see Crazy Frog's photo...it's the contents of the clear plastic bag) . The O ring for the reservoir can be purchased by itself (may be cheaper from Munich Motorcycles than the Stealer...sorry, Dealer.

But mine still leaks slowly, so I may try and find a thicker O ring.


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Neil
K100RS 1986 RED!

Dress for the ride and the potential slide.
    

Ned

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Neil,
When you say BM shop, is that BMW or just a business name?
I notice that all one can get a new master cylinder for around US$110 + PP, so expect US140.

My unit is truly screwed. It barely moved the pads and bottoms out before any effect is noticed. No external leaks.

Now, should I go with a new unit. Or re-sleeve and rebuild. The cost? about the same.

    

Crazy Frog

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Why would you take any chance with a re-sleeved cylinder when you can have
a new one for the same price? Buy it new with warranty.
I would have expected the cost of a new one way higher.
On the K bikes, the master cylinder is made by Magura and not BMW. You may find the parts directly with them and they may be cheaper.
The calipers are Brembo and a lot of Italian bikes are using exactly the same type. Again parts may be cheaper at Ducati or Guzzi.

Bert


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Front master cylinder rebuild...still leaking! Frog15Front master cylinder rebuild...still leaking! Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

blaKey

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Buy a new one...I will be!

The name of the shop is "The BM Shop" (07 3356 6128) 28 Wolverhampton Street, Stafford, Qld, 4053.

You are really in "the lap of the gods" when you buy exchange. But I have rung the BM Shop and told him of my problem and he said to bring the bike in so he can look at it.


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Neil
K100RS 1986 RED!

Dress for the ride and the potential slide.
    

Ned

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@Crazy Frog wrote:Why would you take any chance with a re-sleeved cylinder when you can have
a new one for the same price? Buy it new with warranty.
I would have expected the cost of a new one way higher.
On the K bikes, the master cylinder is made by Magura and not BMW. You may find the parts directly with them and they may be cheaper.
The calipers are Brembo and a lot of Italian bikes are using exactly the same type. Again parts may be cheaper at Ducati or Guzzi.

Bert

Potentially the benefits of using a re-sleeved unit is that they use a stainless sleeve. this eliminates any further corrosion due to water absorbed in glycol (alcohol based brake fluid).
In the past all problems (I've experienced) related to master cylinders was corrosion.


by blakey on Tue Feb 23, 2010 12:01 am

Buy a new one...I will be!

That is definitive Smile I probably will.

    

Crazy Frog

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Thanks for the information.
I didn't know that the re-sleeved was stainless steel.
Now there is something else to consider, the choice becomes more difficult.
If you are planning to keep your bike for many years, stainless steel may be the solution.
Difficult choice........


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Front master cylinder rebuild...still leaking! Frog15Front master cylinder rebuild...still leaking! Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.
    

Ned

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this is what inspired me to ask: Click here

If you look down the page they talk about benefits and it appears that they don't care what you give them, master cylinder or calliper, but do they do bikes ?

I take your point about Barembo brakes. I will look into sourcing things from other suppliers.

    

blaKey

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I sent them an email asking if they do bike master cylinders.

By the way...my resleeve isn't stainless steel, it looks like copper.

And Ned...get back to work or are you on holidays?


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Neil
K100RS 1986 RED!

Dress for the ride and the potential slide.
    

Ned

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I always thought that SS was the material of choice re: resleeve. I am not sure why they would use Cu, being soft, but at any case corrosion would not be a problem.

Yep, I am back. Thank you for the moly and email. I will email tomorrow.

    

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