Started dismantling my 1997 K 1100LT to change all the original fuel lines.  Found a cracked hose coming off the crankcase vent at top left rear of engine, just behind TPS.
Looked in top of airbox and it appeared that the accumulator/oil separator in top of airbox could be taken apart to replace interior mesh by releasing tabs.  Well it cannot be taken apart without major surgery to plastic.  Now that I have mangled the separator I have two choices, buy another airbox top or install a PCV valve on the crankcase vent and connect it to the manifold on the right side of the throttle bodies.

1.  anyone have a good airbox top to sell me?  I would prefer to keep the bike stock unless someone can tell me the bike will run great with #2 modification. Dont want to delete the airbox and want to keep the stock air filter. (i think the non serviceable accumulator in the air box top is a design error by BMW.  the plastic mesh inside deteriorates to nothing.  stainless steel mesh would have been better)
2.  anyone ever done the modification to install a PCV valve to direct crankcase pressure/oil vapor directly into the throttle body rubber manifold.  Does it work well and what PCV valve did you use?  How did you connect hose?
3.  is a catch bottle a better way to go?  where to mount in a K1100LT.

Yes I have read the old posts by Max, 2 wheels, etc.  just no testimonials found on how well the bypass method or catch bottle works.  Obviously, I would plug all the other spigots into the airbox and top of timing cover.

The stock oil separator basically does the same thing as the modification.  the only difference i can see is some additional small amount of oil vapors being directed into the rubber manifold at throttle bodies.  Any problems with that?
thanks all,
Jerome in Portland. OR

BMW does not use a PCV in Bricks. The crankcase is pressurised, so a cracked Z hose (the one you've discovered) will cause poor idling. A tight hose without cracks will present as a poor idle when you remove the oil filler plug while the engine is running. When I put Big Block together, a K1200 engine in an earlier K frame, I simply extended and diverted a breather hose to the back of the throttle bodies, because the rack of TBs are atop 10" stainless steel, curved extenders - no airbox of any kind, just four individual K&N pod filters. The K12 uses a larger rubber tube than K11 but it is similar. I recommend just diverting the crankcase "fumes" to the TBs. See THIS thread by Rolf for his version.

thanks for the reply 2 wheels, I want to keep the stock air filter and air box (without the funky oil separator).  Hoping BMW engineers designed airbox to balance engine air flow with stock exhaust.

Wonder if anyone has done surgery on the separator in the air box top to put some better mesh in it?

Hoping to hear that more than one person has done the hose straight from main crankcase vent to throttle body manifold without PCV valve.

Here's the breather system on any K1200RS or K1200GT Brick. Straight from the vent tube at the back of the block to the base of the TBs.

Thanks, I was looking on realoem for the 1200 diagram but did not find. Now I just need to buy a new rubber 4 outlet manifold because that has small cracks.
Or I could make one

Hi Attitude

Suggest you just bypass the oil separator, plug all the holes and make up a 4 outlet manifold pipe like this one:

 

You can do away with the single inlet and just extend one end of the manifold slightly and connect that to the engine breather with a rubber hose. The micro cracks in the original rubber manifold are bad news for idling. After installing my version the idling is smoother and the bikes seems to perform better. (probably just in my head)

Rolf, I like your version in metal. Rubber version is about $100 at motorworks UK. Would you consider making and selling these? Once a jig is set up it should be profitable.