Should be quite similar issues  between K75 and K100. But 8 years ago I started to refurbish a K75 as a cafe racer. For various reasons including heartbreak, divorce and other idiot reasons I suspended the project after  powder coating the frame and other bits and pieces. Given the COVID-19 shelter in place orders it seems like a good time to restart the project. At this point I'm looking at doing the brakes and getting them re-installed. The engine and both wheels are in place. But the brake calipers are a little rough, i.e. dirty and showing some corrosion at the connectors. So I wire brushed the outside metal and have used brake cleaner to further clean off the outside. Now the original front brakes were earlier model that has a metal tube dropping through the fork tube and ending in a "Y" with brake lines running to either side. The rear is standard and had a bit more aluminum corrosion to the point that the original paint had peeled. I'm looking at the rubber trying to clean it inside and out. Wondering if it is trustworthy or if I can afford to replace them. I've looked up the prices online and groaned a bit. As a kicker a buddy sold me a parts bike for USD $100.  A K75 but with the tranny and rear end missing. And a couple of other pieces. But the front brakes on this bike are the kind with a metal tube under the fender connecting the two front calipers. First thought was to use those but unfortunately the metal tube that drops through the main fork tube is one of the missing bits. Looked into replacing that piece and it was suggested that I just run a braided steel hose from the front brake handle down the side to the right caliper and then the hard steel tube over to the left rside. I'm dithering about which approach to take refurbish the existing hoses or break the bank and get the braided brake line. And then there may a cost to refurb the calipers.

So questions to the assembled experts. Cleaning the brake hose lines. Does that make any sense or does dumping them seem like a necessity. An aside- At this point I'm primarily interested in seeing if the bike can be reassembled and got running. Prettying it up is a secondary concern. Any suggestions on how to clean the rubber brake hoses? Any flaming red flags about what is absolutely impossibly stupid to do?

Likewise with the calipers. Any suggestions of how to test if the existing rubber is still intact and trustworthy. The brake pads themselves look to be decent and I have others to boot. Any warnings? Always seems like there is someone who will tell me all the evil things that could happen. BTW, my main ride is another K75 with a R100RT fairing that has 161,000 miles on it. So I'm now the proud owner of either 2 1/2 bikes or 1 bike and 1 1/2 parts bikes.

It's not expensive to run a SS line from the master to the right caliper and then the metal line to the left caliper. I've done it to several Ks.

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/2vbrakes/2vbrakes.htm

Hi Duck,
Do you remember where you got the part? Just the SS line and banjo's? Prices I've been quoted at this point are $100+. Also does anyone know of a supplier other than BMW for the rubber bits?

Best fairing is from Artus Grape gmbh Look the cafe racer i will now build same

If you don’t mind ordering from UK try these for new and
Used parts.
https://www.motorworks.co.uk/vlive/Home/index.php?gclid=EAIaIQobChMI9bONh9eF6QIVmKztCh3QtgnpEAAYASAAEgJsHfD_BwE

Don't even THINK about using thirty-plus year-old rubber brake lines. They will have deteriorated dangerously by now. If you know a shop that builds stainless brake lines you can reduce the cost by eliminating that damn stupid Y-piece and dropping the lines direct from the master cylinder to each caliper. Yes, it needs a double banjo at the top. As a bonus, you get to be able to grease/inspect the headstock bearings without dismantling the hydraulic system. As a second bonus, they're a lot easier to bleed too.

lion1453 wrote:Best fairing is from Artus Grape gmbh Look the cafe racer i will now build same

Couldn't find a Grape gmbh. Do you have a link to their website?

Dai wrote:Don't even THINK about using thirty-plus year-old rubber brake lines. They will have deteriorated dangerously by now. If you know a shop that builds stainless brake lines you can reduce the cost by eliminating that damn stupid Y-piece and dropping the lines direct from the master cylinder to each caliper. Yes, it needs a double banjo at the top. As a bonus, you get to be able to grease/inspect the headstock bearings without dismantling the hydraulic system. As a second bonus, they're a lot easier to bleed too.

Hi Dai, it's sweet of you to worry. But my main ride, the '91K75 with 161,000 miles, has the original brake lines etc and is still going strong. So at this point I have three sets of right controls with brakes etc. Main issue is that corrosion seems to have affected the brake plunger on one and BMW doesn't sell the rubber bits. Just the whole setup and it's not always available. And my bud, Greg, has the stainless lines which "IF" I can get the bike back up and running then I will look into that. But at the moment I am struggling just to find all the little bits needed to get it back together and prove it can still run. At $20 here and $40 there we're out of the nickeling you to death region. As an example bud, Greg, sold me a parts bike - sans tranny and rear end - for USD $100. and tossed in a 15-20 lb box of odd nuts and bolts off various BMW M/C. Here you might find what you need in here. Have you ever sorted through 15-20 lbs of nuts and bolts. Some are a couple of millimeters long and then there are the M10's. Night after Night with the COVID-19 shelter in place and not much else to do I've been sorting. I'm going bonkers. Just trying to find a screw to hold the back of the instrument pod protective cover in place. Yiii Yiii Yii! Maybe I'll finish it just before the virus does us.

Your local plant hire/mend a hose guy can do SSline with fitting at a LOT LOWER 
PRICE just look around your area,as for new rubber!! too costly to my mind.

Duck has a post for single line with cross over pipe well worth considering at this stage.

moriarti wrote:Your local plant hire/mend a hose guy can do SSline with fitting at a LOT LOWER 
PRICE just look around your area,as for new rubber!! too costly to my mind.

Duck has a post for single line with cross over pipe well worth considering at this stage.

Hi Moriarti,
I've got the cross over pipe. Think it is off the parts bike. So all's needed is the SSline down from the brake grip. But not sure about "Duck's" post. Got a link to it??  Anyway, that all comes after i see/hear the motor running and see what other issues there might be. At the moment I'm sitting here in ...well just got up and waiting for the battery to be delivered. Can't just go out and buy one. You have to do it online due to the COVID 19  shelter in place. Can't even take my cat to the VET. And the battery has been in transit now for a week and not showing as having arrived in this locality. I really don't like shopping on-line.
best regards  guys

First reply on this thread from Duck #2,good luck with the build


As the cross over pipe you have is steel and used i would consider making a copper pipe
wont rust more flexible,and looks good when polished

moriarti wrote:First reply on this thread from Duck #2,good luck with the build


As the cross over pipe you have is steel and used i would consider making a copper pipe
wont rust more flexible,and looks good when polished

Thanks, don't know how I missed Duck's link. Looks good. Great for AFTER, I see the bloody engine, electrics etc working.

I would avoid copper, especially in the smaller diameters.  Vibration will work harden it, possibly leading to cracks and leaks which, of course, will happen at the worst time.

What him above sez. If you've ever had a late British bike with a copper head gasket, you'll know exactly what he means.

Im happy to be corrected,however iv fitted copper brake pipes on many cars  
without any adverse effects.Never too old to learn and the bonus of belonging to
K forum is knowledge 

Don't know about CA, of course, but copper brake lines as a new fitment are illegal in NSW, Oz unless replacing original copper lines, which by now are on very old vehicles.

Bill

indian036 wrote:Don't know about CA, of course, but copper brake lines as a new fitment are illegal in NSW, Oz unless replacing original copper lines, which by now are on very old vehicles.

Bill

Well, if we're talking about my situation as OP, the cross over brake line will be off another BMW K75 which I have. As President of the CheapASS Bastards Of America, I'm politically, morally, and financially against buying anything else. 'Course then there was today when I actually spent USD $20. for a complete K75C instrument pod (outer plastic) and a R100RT upper fairing with "FOLD OUT LIGHTS".  Admittedly the R100RT fairing does have a few cracks but those are easily remedied with epoxy. Something I've done before. But my main ride, the K75 with 161,000 miles has an R-RT fairing on it. And now I have a set of the fold out lights which I will install in place of the air vents. Oh, sorry can't insert a photo. Understandable as that probably takes up too much space on the server. As Prez. of the CABofA I understand fully. Anyway, it was only $20. which I can rationalize away. And with installation of proper LED's in the fold outs I'm sure to project far more light than any other mortal on the road.