Options for master cylinder replacement R75/6

[Porge]

Guys,

Just in case I get nowhere with the master cylinder on the R75/6, what should I be looking for to replace the master cylinder? The castings on the bike mark it a 11/74 build. It has the later switchgear on the rhs. I've read that later mono lever bikes have fairly easily switched over gear - should I be trawling eBay for anything in particular?


Tanks in advance.

[SteveD]

Yep.

I changed my wooden 15mm MC on a R100RS 11/1981 for a mono 13mm. More feel, more progressive, the lever moves further. Not too much further. It's comfortable.

ebay.de in the faterland is a great source. They're popular, so not necessarily cheap.

[Ken in Oklahoma]

Guys, Just in case I get nowhere with the master cylinder on the R75/6, what should I be looking for to replace the master cylinder? The castings on the bike mark it a 11/74 build. It has the later switchgear on the rhs. I've read that later mono lever bikes have fairly easily switched over gear - should I be trawling eBay for anything in particular?

I don't know enough to definitively answer your question, and especially I know little about the mono lever based conversion. So I'll give you what I think I know. Having said that, my understanding is that you're likely to end up with later switchgear and master cylinder associated with pre-mono bikes. But like I say, I'm not so familiar with them.

I have a '76 R75/6 and have pondered changing the required parts myself. If I remember correctly Motobins offered kits to make the change. Perhaps they still do.

Another question that will surely come up in your mind is whether or not to go with dual disks in front a la the R90S, R100S, R100RS bikes which were factory equipped with them in conjunction with the under tank master cylinders. The largest obstacle in this approach is securing that increasingly rare and expensive R/H fork slider to mount the second swinging ATE caliper. Your total expenditure is likely to go into the low hundreds of dollars.

You will also be doing a bit of rewiring since the later controls will differ a bit from what you have now.

I'm not sure, but I believe there are people somewhere who will bore and sleeve your existing under tank master cylinder. That would surely be the cheapest and a decent option. FYI the stock under tank single disk master cylinders have a different bore diameter from the dual disk under tank master cylinders. Properly taken care of a "new' under tank will serve you well, though you will only have braking as good as the original setup plus presumably better pads for the ATE caliper you have.

I am loathe to say this since in the past I have taken issue with Duane Ausherman's suggestion that folks search the internet first before coming here to Boxerworks. My point of view is that we have a lot of people here who know a lot of airheads stuff and have excellent advice to offer. But in the absence of detailed information (which you're not getting from me) I would browse the internet to see what I could come up with. Your (and my) problem has been around for a long time and a lot of people have come up with solutions.

Hopefully, though, somebody will come along and give you some definitive inputs.

Ken

[Rob]

Yes, Motobins offers a kit:

https://www.motobins.co.uk/bmw-parts.ph ... lve%20Twin

Look for part# 61170

61171 if it is an RS or RT.

[Porge]

Have found a couple of potential buys, and will chase them up. My 13 year old was over for the first time since picking her up (the end old holidays were with his mum this year), and he's keen to go out for a trip ASAP. I'll have to crack on . I like the look of Charlie's conversion. Gosh darn my newer switchgear!


Another factor that's slightly painful is the bleed nipple on the caliber. It's in solid. There were some signs of bodging on it when I first started on it, and I foolishly reached for the sidchrome...not the 6 sider. Should have hammered one of those one first up . In my defence, I did soak it in wd40 for a couple of days beforehand.

So. The nipple is chewed. Thinking of filing some flats on it, and reaching for he multigrips. Thoughts?

[SteveD]

You should be able to buy nipples.

Avoiding thread damage might be the issue.

Double entendres rule.

[Major Softie]

You should be able to buy nipples.

Avoiding thread damage might be the issue.

Double entendres rule.

This thread seems fine to me.....

[SteveD]

Not as coarse as some! Good one Major.

[Porge]

Went heat and mole grips on the nipple, removed it, replaced with with a slightly longer one. For giggles, I thought I'd flush it out with fluid....no leaks. No sponginess at the lever. And now I have brakes!

Found in a box what I now know to be the rest of the fuel cap parts. Have assembled by tapping the hole for the "rivet", and screwing in a nice looking screw, with an appropriate washer.

Buying a battery tomorrow, and am thinking about a sneaky lap around the block to assess what else might need doing before going over the pits. I'm going for a ready rider, not a resto at the moment.

[Rob]

If I were you, I would take that brake caliper apart and remove the cylinder to see what kind of gunk lies in there. Mine was a mess, when I took it apart, and it was a 1-owner machine!