The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: chrisr65ls on January 28, 2013, 09:30:53 PM
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The brake handle on my 84LS is getting fairly 'lumpy' and I can see where fluid has leaked onto the handle and housing.
A friend said that the seals will need replacing and it will probably need machining as well.
Is sounds like an expensive exercise.
Would I be better off getting an already reconditioned unit instead?
What sort of price should I expect for this work and how long does it take?
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About 50% of the time master cylinders are rebuildable with just a little clean up. No way of knowing till it's all apart and you take a look. You need to watch for pitting in the bore, and seals with rounded edges. It's difficult to describe on the seals, but if there's much in the way of large pits, the master will need sleeving. If the bore is ok, a rebuild kit should do it. There have been times all I've needed to do was clean everything up and put it back together to have it all fixed.
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I'm pretty sure you won't find any separate seals, you will need to buy a piston kit which comes assembled and complete with dust seal and washer ready to slide into your master cylinder once you clean up and check the bore. I've done mine 3 times and it still works fine.
I hone the bore with 2000grit wet and dry paper wrapped around a dowell. Just remember to only hone in a circular direction, not longitudinally, or it may be more prone to leak.
Don't forget to check the TINY fluid return hole to make sure it's not blocked, while you are cleaning things up.
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Conversely, if you can't get it nailed down with a rebuild, the original part is available. I bit the bullet (after attempting to rebuild) and bought a new master cylinder a year or two ago.. cost 150$ USD I think, but I ordered it from ... motobins maybe? definitely overseas.. it was cheaper than any dealer I could find stateside.
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I think that piston kit that Bruce mentioned is over a hundred bucks. I had to go that route, but it was long enough ago that the memories are blessedly faded. Yeah I change my brake fluid....
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Yes they were $100 Australian 4 years ago, I had a good look for rubbers to fit but with no luck.