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Thread: '87 K100RT My Flying Brick Stinks! Why?

  1. #1
    RK Ryder
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    '87 K100RT My Flying Brick Stinks! Why?

    Last year I exclusively rode my K in the spring but then parked in on the bike lift, on the side stand until mid-September. Sort of forgot about it because my R was running so smoothly.

    So when I finally got back on the K, it would stink of gasoline for maybe the first thirty minutes before the air would clear. Even ran the tank quite empty a couple of times and refilled it with fresh ethanol free gas. Always the same, smelly gasoline odour for the first 30 minutes or so of the ride. Parked it for the winter on its' centre stand with fresh ethanol free gasoline in the tank.

    Took it out today for the first ride of the season (with 267,00 km on the odometre). Same smell for the first part of the ride. No odours when returned home.

    Can anyone suggest where the problem might lie?
    Paul
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
    Niagara Riders & Knights of the Roundel #333

  2. #2
    Registered User 6322's Avatar
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    Sounds like a fuel line leak or loose clamp.
    Gary Phillips - #6322
    Wildland Firefighter, Retired, Riggins, ID
    Heartland Moto Locos BMW Riders
    '77 R100/7 Dirt Hack, '83 R80ST, '85 K100RS w/EML, '00 R1100RS

  3. #3
    RK Ryder
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    Quote Originally Posted by 6322 View Post
    Sounds like a fuel line leak or loose clamp.
    Is that a possibility as there have been no puddles of gas in the garage?
    Paul
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
    Niagara Riders & Knights of the Roundel #333

  4. #4
    The classic K bikes originally had vent and drain lines from the tank to the right foot peg area. Then a rectangular funnel device (called an air accumulator) was used to place beneath the drain and vent stub pipes on the tank with a single hose down to the right foot peg area. On my several K75s this has caused fuel odors as you have described because the tank vent is open to the atmosphere at waist level instead of below ankle level. This may be what you are encountering. Raise the rear of the tank and see if you have the air accumulator and if not, see if the vent hose is attached to the stub pipe on the tank.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  5. #5
    RK Ryder
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    Quote Originally Posted by 6322 View Post
    Sounds like a fuel line leak or loose clamp.
    Quote Originally Posted by PGlaves View Post
    The classic K bikes originally had vent and drain lines from the tank to the right foot peg area. Then a rectangular funnel device (called an air accumulator) was used to place beneath the drain and vent stub pipes on the tank with a single hose down to the right foot peg area. On my several K75s this has caused fuel odors as you have described because the tank vent is open to the atmosphere at waist level instead of below ankle level. This may be what you are encountering. Raise the rear of the tank and see if you have the air accumulator and if not, see if the vent hose is attached to the stub pipe on the tank.
    Thank you for these suggestions.

    Today will not work for looking at the K but I will look at it this week. The gas tank was off in the winter of 2018 and although I don't recall a gasoline fumes in the spring of '18, I really did not ride the bike much until the fall. Possibly I did not put the tank back on correctly or tighten the hose clamp properly.
    Paul
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
    Niagara Riders & Knights of the Roundel #333

  6. #6
    RK Ryder
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    I just looked at the bike and no vent hose is visible hanging on the right side!!!

    When look into the bike more closely and discover that my vent hose has vanished, must I have BMW OEM hose or can a local auto parts store supply an equivalent. If so what characteristics must the hose have?
    Paul
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
    Niagara Riders & Knights of the Roundel #333

  7. #7
    Registered User
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    I think any gasoline rated hose of the correct diameter would be fine.

    Take the collection cup with you and find something that fits correctly.

  8. #8
    Registered User GTRider's Avatar
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    Quote Originally Posted by Paul_F View Post
    I just looked at the bike and no vent hose is visible hanging on the right side!!!

    When look into the bike more closely and discover that my vent hose has vanished, must I have BMW OEM hose or can a local auto parts store supply an equivalent. If so what characteristics must the hose have?
    Most of the fuel or vacuum line sold at auto parts stores is fairly thick-walled, thus harder to route than it needs to be. If you don’t want to buy BMW tubing, which is thinner-walled, determine the ID you want then do a search on Amazon for “rubber tubing”. You’ll find a variety of sizes, lengths, etc. so pick the ID you need. Lots of options in 1/16” wall tubing, which is plenty heavy enough for your vent line. Beyond that, try to get a fuel-rated version but I wouldn’t stress over that part too much on an atmospheric vent line. Age, heat, and atmospheric ozone will destroy it as much or more than fuel fumes.

    Best,
    DG
    DGerber
    1983 R80ST — 1984 R80 G/S PD — 1993 R100GS — 2004 K1200GT w/Hannigan S/C — 2010 K1300GT
    BMWMOA#52184, AMA#271542, IBA#138

  9. #9
    3 Red Bricks
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    Paul,

    Please remember to include the year and model of the bike IN THE TITLE of your thread. I've added it for you this time.

    Thanks.




    Last edited by 98lee; 04-15-2019 at 07:09 PM.
    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

  10. #10
    Registered User drneo66's Avatar
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    I'd also take a look the seals in/around your gas cap - they aren't getting any younger...

    Bob's BMW has a rebuild kit (you have to call, as it's not listed on their website) and Chris Harris has a Youtube video on how to refresh the seals.
    Current: 2007 BMW R1200RT
    Former: 1995 BMW K75S, 2009 BMW G650GS
    MOA Member #:150400, IBA#: 37558

  11. #11
    3 Red Bricks
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    The bikes that didn't come with "the cup" (air accumulator) had the tank vented to the crankcase.

    The tank vent is the forward nipple underneath the tank about 7" from the rear of the tank just to the right of the centerline. The vent hose runs forward, through a check valve, to a nipple on top of the front of the block just below the fan. Most US smog spec. bikes are vented this way.




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

  12. #12
    Quote Originally Posted by 98lee View Post
    The bikes that didn't come with "the cup" (air accumulator) had the tank vented to the crankcase.

    The tank vent is the forward nipple underneath the tank about 7" from the rear of the tank just to the right of the centerline. The vent hose runs forward, through a check valve, to a nipple on top of the front of the block just below the fan. Most US smog spec. bikes are vented this way.




    When I bought my K75T in 1986 the dealer re-routed the vent away from the crankcase at the 600 mile service. The issue was/is that if the tank were to be overfilled, or even if not, if left sitting in the hot sun right after a fillup, it can puke raw gas into the crankcase and dilute the oil. If you have one still vented to the crankcase I would cap the stub pipe at the engine and add an air accumulator (little square funnel) or just run the vent line to the right footpeg area.
    Last edited by PGlaves; 04-16-2019 at 02:25 PM.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  13. #13
    3 Red Bricks
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    I have changed all 6 of my K75Ss over to the cup and I change every bike I work on over.

    I find about half the bikes that come in for the first time have nothing, no cup and a disconnected hose to the crankcase(which creates a vacuum leak and lean mixture).




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

  14. #14

    Reply

    I think you should go to some mechanic that will be the finest way to resolve this issue ...

  15. #15
    RK Ryder
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    Quote Originally Posted by stevenjones999 View Post
    I think you should go to some mechanic that will be the finest way to resolve this issue ...
    Once I get this issue solved, https://forums.bmwmoa.org/showthread...ay-Suggestions

    that will be the next step. Nothing seemed out of order when I removed the gas tank but the seals around the gas tank looked rather wretched. Hence I replaced them and a new problem arose.
    Paul
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
    Niagara Riders & Knights of the Roundel #333

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