I have made a plan to solve or reduce the costs of our age old headache with the breather hoses that perish and cause rough and irregular idling.

For the K75 and K100 2V I managed to get a local rubber component manufacturer to make the "Z" pipes at a fraction of the BMW price. (USD 6 +/-) See the pic below. If anyone needs I can have some made up but it's normally the shipping from SA that becomes costly. The one on the left is the original.



For the K100 4V and the K1100 breather rail at the back of the throttle bodies (develops micro cracks), I just made up a pipe out of 15mm copper piping and brazed on the 4 nipples and closed the ends. The inlet is straight in and works well by just cutting the rubber hose that comes from the air box shorter. The rail is attached to the TB with rubber hoses as per the 2 nipples on the right.



Hope this is helpfull to some.

Have you installed and road-tested that z-pipe yet?

My friend has installed one on his K100RS and ... so far so good. I have not replaced the one on my K75 yet but will soon. 

The original Z pipes are moulded and obviously the rubber compound does not last as long as one would hope. I asked my manufacturer to make sure he uses rubber that is oil resistant. It feels like proper rubber and not plastic'y like the original.

I am working on fabbing a header with copper tubing and fittings. Will report back when it comes together with soldered joints.

Rolf E wrote:The original Z pipes are moulded and obviously the rubber compound does not last as long as one would hope. I asked my manufacturer to make sure he uses rubber that is oil resistant. It feels like proper rubber and not plastic'y like the original.

The rubber tube at the back of the throttle bodies, which has a softer "feel" to it compared to the Z pipe, is recommended by BMW (on the K1200 series) to be replaced at 60,000 miles, and that's about the life to expect of them. I haven't ever recorded the life of the various Z tubes on the early series K bikes I've owned but imagine it is something similar. By 90,000 kilometres I'd replaced the deteriorating Z pipe on my '87 K100RS Down Undah.

I've replaced LFB's crankcase breather twice in 111,000 miles. Last time I made one from Guzzi breather box pipework which is much thicker and, to my own knowledge, good for around 150,000 miles before they finally go hard. They do crack but only if you clamp them up too hard.

The durability is probably not just a matter of km or miles but also age and heat. It is not uncommon for my cooling fan to run when riding through town on a hot summers day. The cooling fan on the K100RS 4V comes on at 105 deg C. In the generally colder parts of the world they may last longer but all this is speculation until proper research has been done. For the cost of my replacement options, it's not worth the effort. 

The last couple of weeks we've been through a heat wave. The temp indicator in my VW commonly showed 38 deg C and at one time went as high as 46 deg C.  

BTW attitude, I would suggest you braze rather than solder. If that's a problem for you let me know. 

I have fabricated a copper header and connected that directly to the crankcase vent spigot at the top rear of engine.  Would a check valve be necessary at crankcase connection?  Is there a check valve in the stock non serviceable separator in the airbox?  Bike has good compression and not using oil.

Obviously I am learning how to insert a photo

That looks like it can do the job. I just can't clearly see how you are connecting the breather to the manifold? I doubt there is a check valve in the original system and would go without one. You must just check that you air box still fits and the breather manifold does not interfere.

No check valve. The only bikes that had one (to my knowledge) were 83-85 2v and that was in the fuel tank. Nasty rattly thing.