Page 1 of 2 1 2 LastLast
Results 1 to 15 of 19

Thread: 1994 K75S Z Hose Question

  1. #1
    Slipster Slipster's Avatar
    Join Date
    Jun 2012
    Location
    Broken Arrow, OK
    Posts
    72

    1994 K75S Z Hose Question

    Well I have been into the bike replacing rubber bits here and there. Just did a O Rings change in the starter, Alternator Monkey Nuts etc. etc. etc. I also found a tear in the Z hose. It ripped apart when I removed it. A new one is on the way. I cranked the bike over after putting it all back together again just to hear if the starter and alternator were ok. I had no Z hose installed. The bike starts but will not run.

    So my question is one of better understanding what the Z Hose actually does and how that little hose can prevent the motor from running ?? IMPORTANT little hose
    Expect The Unexpected

  2. #2
    3 Red Bricks
    Join Date
    Jan 2007
    Location
    Pleasanton, Ca.
    Posts
    3,157
    It will not run without the Crankcase vent hose (Z hose).

    The Crankcase vent hose does what its name implies. It vents the crankcase (into the intake plenum).

    It vents it into the plenum above the throttle bodies AFTER THE AIR FLOW METER. Any air that gets into the plenum is unmetered air, meaning that the computer does not know it is there and does not inject enough fuel to compensate for it. Therefore, the mixture is way too lean to properly run. A similar situation will happen if you have the hose in place and remove the oil filler cap (happens on most modern cars too).

    SMALL cracks in that hose will lean out the mixture enough to cause a multitude of problems (poor idle, burned valves, etc.) and that hose is VERY thin and in the hottest part of the bike. The cracks will happen just below the upper hose clamp and just above the lower hose clamp. These hoses usually require changing every couple years but need to be checked WAY more often ( at LEAST once a year).



    Last edited by 98lee; 11-21-2012 at 03:17 AM.
    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  3. #3
    Slipster Slipster's Avatar
    Join Date
    Jun 2012
    Location
    Broken Arrow, OK
    Posts
    72
    Thank you Lee for your detailed response to my question. I understand now and will definitely check the hose every year from here on out
    Expect The Unexpected

  4. #4
    Registered User kgadley01's Avatar
    Join Date
    Dec 2006
    Location
    South Carolina
    Posts
    3,520
    Thats good info...
    AKA SNAPGADGET
    Lifes too short to ride an ugly Motorcycle

  5. #5
    Registered User argent brick's Avatar
    Join Date
    Aug 2012
    Location
    Wine Country, Northern California
    Posts
    461
    Quote Originally Posted by 98lee View Post
    It will not run without the Crankcase vent hose (Z hose).

    The Crankcase vent hose does what its name implies. It vents the crankcase (into the intake plenum).

    It vents it into the plenum above the throttle bodies AFTER THE AIR FLOW METER. Any air that gets into the plenum is unmetered air, meaning that the computer does not know it is there and does not inject enough fuel to compensate for it. Therefore, the mixture is way too lean to properly run. A similar situation will happen if you have the hose in place and remove the oil filler cap (happens on most modern cars too).

    SMALL cracks in that hose will lean out the mixture enough to cause a multitude of problems (poor idle, burned valves, etc.) and that hose is VERY thin and in the hottest part of the bike. The cracks will happen just below the upper hose clamp and just above the lower hose clamp. These hoses usually require changing every couple years but need to be checked WAY more often ( at LEAST once a year).
    Hey Lee,

    Mine has cracks in it. Do you have a part number?
    Lynn
    MOA #57883
    Current Ride: 1995 K75 Standard
    Past: 1978 Yamaha XS 750, 1976 BMW R60/6

  6. #6
    3 Red Bricks
    Join Date
    Jan 2007
    Location
    Pleasanton, Ca.
    Posts
    3,157
    11 15 1 460 480 VENT HOSE $15.56



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  7. #7
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Albuquerque, New Mexico
    Posts
    1,083
    Quote Originally Posted by ARGENT BRICK View Post
    Hey Lee,

    Mine has cracks in it. Do you have a part number?
    Hey, Lynn; that might be part of the reason you are getting poor mpg as posted in your other thread.

    Mine was cracked as I discovered a couple months ago during another procedure---when I installed a new Z-hose it made a world of difference!
    ---Jeff '94 K75S Berlina

    ex: R100GS/PD , K100RS , R75/5 , R60/2

  8. #8
    Dum vivimus vivamus ted's Avatar
    Join Date
    Mar 2003
    Posts
    2,576
    A thread I started when I changed mine some time ago, with pics and replacement info
    http://www.bmwmoa.org/forum/showthread.php?t=56654

    A good lesson that these hoses may look fine but should still be changed with some regularity.
    Ted
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

  9. #9
    Registered User argent brick's Avatar
    Join Date
    Aug 2012
    Location
    Wine Country, Northern California
    Posts
    461
    Quote Originally Posted by 98lee View Post
    11 15 1 460 480 VENT HOSE $15.56
    Thanks, Lee.

    My BMW dealer is not that far away from the local VA hospital, and I figured that I would hit both in one trip, or so I thought. I dropped by the dealer to pick up the hose, and, of course, they did not have it in stock. They only keep one in stock and it was sold last week. Just my luck.
    Lynn
    MOA #57883
    Current Ride: 1995 K75 Standard
    Past: 1978 Yamaha XS 750, 1976 BMW R60/6

  10. #10
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Albuquerque, New Mexico
    Posts
    1,083
    I hope you ordered one, nonetheless! Among the best purchases one can make.
    ---Jeff '94 K75S Berlina

    ex: R100GS/PD , K100RS , R75/5 , R60/2

  11. #11
    Registered User argent brick's Avatar
    Join Date
    Aug 2012
    Location
    Wine Country, Northern California
    Posts
    461
    Quote Originally Posted by Zagando View Post
    I hope you ordered one, nonetheless! Among the best purchases one can make.
    Yeah, I did. The nice thing was that my dealer did not consider it a special order, so I did not not have to pay for it yet. It just frost my rear end when dealers insist upon payment up front on everything. I can see it on clothing, helmets and such, but not on normal maintenance parts. Especially if it is something that they normally stock.
    I understand why they do it, though.

    A friend of mine who is a service manager suggested that we make one out of fuel line and metal fittings. I wonder, has anyone made their own?
    Lynn
    MOA #57883
    Current Ride: 1995 K75 Standard
    Past: 1978 Yamaha XS 750, 1976 BMW R60/6

  12. #12
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Albuquerque, New Mexico
    Posts
    1,083
    Good question, Lynn and I know others have used certain larger diameter rubber hose to replace the Z-hose with---but if fuel line was used it would also have to be larger than the 8x13mm BMW standard. Check the ends for the correct diameter needed; might be in the neighborhood of 18-20mm is my guess.

    Do not try the aftermarket Z-hoses (even the ones Beemerboneyard sells) as 98Lee advises us that they are even more flimsy than the OEM ones (and he is one who really knows of where he speaks).

    But maybe a stout large diameter (truck?) fuel line would work just as well? On the other hand, maybe the Z-shape would require too much sharp bending, thereby cutting off the very pressure that needs to be vented in the first place. Interesting to see what the gurus say about this.

    Don/Paul/Lee/Ted to the nearest white courtesy phone, please!
    ---Jeff '94 K75S Berlina

    ex: R100GS/PD , K100RS , R75/5 , R60/2

  13. #13
    3 Red Bricks
    Join Date
    Jan 2007
    Location
    Pleasanton, Ca.
    Posts
    3,157
    I think the hardest part of making a more sturdy replacement would be to also make it flexible enough that you could actually install it. There's not a lot of room there for larger diameter hose. That being said, if you can install it (and that's a serious IF) and it doesn't leak, it would work.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  14. #14
    What, me worry? GILLY's Avatar
    Join Date
    Jul 2007
    Location
    Evansville, WI
    Posts
    1,918
    I had the airbox eliminator on the 87 S that I owned and I only remember replacing that hose once. I think the eliminator really helped keep that over the engine area cooler, which made the hose last longer. Kind of a stretch for a reason for the eliminator, it did get a lot of looks.
    87 K75S, bought new, now sold
    07 K1200GT Bought new, now traded in
    13 C650GT
    MOA 44606

  15. #15
    Registered User 58058D's Avatar
    Join Date
    Jun 2007
    Location
    Mendocino, CA USA about as far left as you can get in the lower 48
    Posts
    693
    Well, that $15 is just unfair....the K12RS only has the 'full distribution hose' unit available and the last time I purchased one it ran over $50 and now it runs over $75....usually it is just the Z shaped part that goes, but not always, but it is only available in the whole assembly these days. Still quite hard to replace.
    Jim Douglas '00 K1200RS >132,000 miles my primary bike again,
    Gone: '09 K1300S sold @ 22k mi, '93 K1100RS traded @ 78k mi, '85 K100RS sold @ 44k mi
    '06 Kaw 650R track bike sold
    http://www.seagullbb.com/

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •