BMW K bikes (Bricks)


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Rolf E

Rolf E
Silver member
Silver member
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.

Engine breather hoses for K75, K100 2V & 4V and K1100 20241210

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.

Engine breather hoses for K75, K100 2V & 4V and K1100 20241211

Hope this is helpfull to some.


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1991 K100RS 16V VIN: K100RS 0200487 Engine# 104EB 3790 2230 Charcoal 166000km
1991 K100RS 16V VIN: K100RS 6408910 Engine# 104EB 2290 2130 Pearl White 217000km
1991 K100RS 16V VIN: K100RS 0200487 Engine# 104EB 1091 2053 Pearl White 77000km
1989 K75s VIN: K75s 0108752 Engine# 753EA42894104
https://www.teuntin.co.za
    

Laitch

Laitch
Life time member
Life time member
Have you installed and road-tested that z-pipe yet?


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1995 K75 90,000 miles
    

Rolf E

Rolf E
Silver member
Silver member
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.

https://www.teuntin.co.za
    

attitude

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

    

Two Wheels Better

Two Wheels Better
Moderator
Moderator
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.


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The forest was shrinking, but the trees kept voting for the axe, for the axe was clever, and convinced the trees that because his handle was made of wood, he was one of them. -Turkish proverb
1977 R75/7-100, '93 K11/K12 Big Block, '93 K1100RS, '95 R100 Mystic, '96 K1100RS, 2 x '98 K1200RS, '06 K1200R & '09 K1300GT
    

Dai

Dai
Life time member
Life time member
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.


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1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

Rolf E

Rolf E
Silver member
Silver member
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.  Smile

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. affraid  

BTW attitude, I would suggest you braze rather than solder. If that's a problem for you let me know.  Engine breather hoses for K75, K100 2V & 4V and K1100 112350


__________________________________________________
1991 K100RS 16V VIN: K100RS 0200487 Engine# 104EB 3790 2230 Charcoal 166000km
1991 K100RS 16V VIN: K100RS 6408910 Engine# 104EB 2290 2130 Pearl White 217000km
1991 K100RS 16V VIN: K100RS 0200487 Engine# 104EB 1091 2053 Pearl White 77000km
1989 K75s VIN: K75s 0108752 Engine# 753EA42894104
https://www.teuntin.co.za
    

attitude

attitude
active member
active member
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.
Engine breather hoses for K75, K100 2V & 4V and K1100 20250110Engine breather hoses for K75, K100 2V & 4V and K1100 20250110

    

attitude

attitude
active member
active member
Obviously I am learning how to insert a photo

    

Rolf E

Rolf E
Silver member
Silver member
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.


__________________________________________________
1991 K100RS 16V VIN: K100RS 0200487 Engine# 104EB 3790 2230 Charcoal 166000km
1991 K100RS 16V VIN: K100RS 6408910 Engine# 104EB 2290 2130 Pearl White 217000km
1991 K100RS 16V VIN: K100RS 0200487 Engine# 104EB 1091 2053 Pearl White 77000km
1989 K75s VIN: K75s 0108752 Engine# 753EA42894104
https://www.teuntin.co.za
    

Dai

Dai
Life time member
Life time member
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.


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

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