Page 1 of 2 1 2 LastLast
Results 1 to 15 of 17

Thread: Tank vent plugged 92 R100RS

  1. #1
    Registered User JGREGOR1.JG's Avatar
    Join Date
    Nov 2013
    Location
    southern CT, USA
    Posts
    79

    Tank vent plugged 92 R100RS

    As I am riding this bike more I am finding small issues to work through. This one is annoying though. She basically runs out of fuel. I keep the flap UP on the tank cap so I can quick open it a bit then she runs fine a while and I do the same.
    I found the vent hose and couldn't blow through it. Put compressed air in it and then I could blow through it but only a small amount. Put the bike back in service and it's plugged again like I never did anything.
    Installed the tie wraps gently. No kinks in hose. Have seen (online) many with this issue and only one fellow that said drill a hole in gas cap, off center pointing out. I cant imagine the design failed right out of the showroom so what has since failed I wonder? I kind of don't want to drill the gas cap.
    Jim Gregory
    92 R100RS
    05 Sportster Roadster

  2. #2
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    13,068
    The vent hose you mention...is this the hose that comes out of the bottom of the tank and is routed to the middle of the bike below the swingarm? I have a similar hose on my /7 and it is not a vent but rather a drain. It simple drains water/gas that might collect in the neck of the filler due to spillage or rain/moisture seeping in.

    The tank should vent through the cap. It must have built up some corrosion such that it doesn't breather anymore...would love to hear how to clear that. I thought the hole drilling was more for freeing up a stuck cap, but there might be more than one reason for a hole.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Registered User JGREGOR1.JG's Avatar
    Join Date
    Nov 2013
    Location
    southern CT, USA
    Posts
    79
    Quote Originally Posted by 20774 View Post
    The vent hose you mention...is this the hose that comes out of the bottom of the tank and is routed to the middle of the bike below the swingarm? I have a similar hose on my /7 and it is not a vent but rather a drain. It simple drains water/gas that might collect in the neck of the filler due to spillage or rain/moisture seeping in.

    The tank should vent through the cap. It must have built up some corrosion such that it doesn't breather anymore...would love to hear how to clear that. I thought the hole drilling was more for freeing up a stuck cap, but there might be more than one reason for a hole.
    Yes I have that hose that drains the neck and on the newer bikes there is a hose next to it that is the tank vent.
    Jim Gregory
    92 R100RS
    05 Sportster Roadster

  4. #4
    Sir Darby Darryl Cainey's Avatar
    Join Date
    Mar 2003
    Location
    Fenwick, Ontario Canada
    Posts
    2,153
    The vent is in the gas tank cap that is plugged, not the tank!
    Ambassador BMW MOA Ontario Canada
    President Niagara BMW Riders #298
    Knights of the Roundel #333
    1977 R100RS, (Retired) 1993 R100GS (just getting started)

  5. #5
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    13,068
    OK, another line on the later models. Have your read Snowbum's article on gas caps? Look near the bottom of this where he talks about venting of the later Airheads which is not through the cap but is part of the SHED system. This is probably where you heard about converting a SHED gas cap to a non-SHED cap.

    http://bmwmotorcycletech.info/fuelfltrs&petcocks.htm
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  6. #6
    Registered User
    Join Date
    Dec 2007
    Posts
    13
    I have the identical bike and had the same problem.

    1988 through 1993 RS models have two hoses coming from the bottom of the tank. One is a drain, as Kurt says, but the other is a vent that goes to the SHED anti pollution system on these bikes.

    When I bought my bike the previous owner had removed all of the SHED equipment and routed the vent hose from the tank to the same area that the drain hose occupies at the swing arm pivot. After riding through a road-resurfacing area my bike seemed starved for fuel. When I loosened the gas cap a little it ran fine. A little head scratching and close inspection revealed a small tar-coated stone stuck right over the end of the vent hose -- stone removed, problem solved.

    If your bike has had the SHED system removed (many have) look for the vent hose -- it's the one on the bottom of the tank toward the front. If not, the vent may be plugged within the SHED system valves and hoses.

  7. #7
    Registered User
    Join Date
    Dec 2007
    Posts
    13
    Forgot to say that the caps on earlier models were vented but those on the 88 through 93 (with the SHED system) were not.

  8. #8
    Registered User JGREGOR1.JG's Avatar
    Join Date
    Nov 2013
    Location
    southern CT, USA
    Posts
    79
    Pretty sure I have the shed system still.
    I did see this on Max's parts site. Copy and pasted

    "This is a SHED cap. We do NOT recommend it. It may cause a venting problem due to vapor lock. Instead, what we recommend is PN 51252307168. This is a Euro cap but found on some USA models. Included with is is a lock cylinder and key. The PN for a NON SHED cap w/out lock cylinder is 51252307125."

    So how do I convert to a non shed cap? Perhaps drill that hole I spoke of??
    Non shed cap is 135 bucks..I'll drill lot's of holes for that. Thing is I'm trying to keep the bike as issued. I may fail at that though.
    Jim Gregory
    92 R100RS
    05 Sportster Roadster

  9. #9
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    13,068
    I don't know enough about the SHED system to understand where it SHOULD vent from. If you knew that, you could fix the problem properly.

    But, it seems from the instructions on Snowbum's site, that the drilling is strictly on the underside...not visible from above. If that's the case, I'd be inclined to do it since only you'll know about it!!
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  10. #10
    Registered User JGREGOR1.JG's Avatar
    Join Date
    Nov 2013
    Location
    southern CT, USA
    Posts
    79
    Quote Originally Posted by 20774 View Post
    I don't know enough about the SHED system to understand where it SHOULD vent from. If you knew that, you could fix the problem properly.

    But, it seems from the instructions on Snowbum's site, that the drilling is strictly on the underside...not visible from above. If that's the case, I'd be inclined to do it since only you'll know about it!!
    True enough. I am still hoping to hear from someone who has actually fixed this issue. My problem is time..I think I will wind up delving into it semi blind (have manual) but I just don't have the time. If I didn't ride to work I would never see my bikes! With today's technology at my keyboard I like knowing exactly where I'm going and what I'm doing before I do it. Man I'm spoiled. I just used to DO stuff back in the day. But I had plenty of time..
    Jim Gregory
    92 R100RS
    05 Sportster Roadster

  11. #11
    Registered User toooldtocare's Avatar
    Join Date
    Mar 2008
    Location
    Lake Saint Louis, MO
    Posts
    1,722
    On a couple of my bikes I removed the shed system, once because it cut off the gas to the carbs due to a bad solenoid. The other time to prevent being stranded like i had been. Here is a diagram of the system from http://www.bmwmcchattanooga.com/show...ssembly=191718

    One of the solenoids vents the vapors from the tank to the engine when the key is off. (11 in diagram) Turning on the key you may hear a hiss as the solenoid changes again and now vents those vapors to the air box allowing them to be burned.

    The other solenoid controls gas to the carbs so when the key is off, it shuts off the fuel. (10 in the diagram) That is the one that went bad on mine bike, starving the engine for gas. The system (from my understanding) does little to hurt performance, and removing it will not gain anything, except a more reliable bike.

    Hope this helps. Haynes manuals have the same diagram, but easier to see. They also explain it better. Removing the system will eliminate the problem you are having because you now add another tube to vent the tank.

    Also, here is a good procedure to remove it if you want. http://www.webbikeworld.com/Motorcyc...les/pulse-air/

    If you do not have the Haynes manual, let me know and I can copy it and post it here.
    Attached Images Attached Images

  12. #12
    Registered User JGREGOR1.JG's Avatar
    Join Date
    Nov 2013
    Location
    southern CT, USA
    Posts
    79
    Quote Originally Posted by toooldtocare View Post
    On a couple of my bikes I removed the shed system, once because it cut off the gas to the carbs due to a bad solenoid. The other time to prevent being stranded like i had been. Here is a diagram of the system from http://www.bmwmcchattanooga.com/show...ssembly=191718

    One of the solenoids vents the vapors from the tank to the engine when the key is off. (11 in diagram) Turning on the key you may hear a hiss as the solenoid changes again and now vents those vapors to the air box allowing them to be burned.

    The other solenoid controls gas to the carbs so when the key is off, it shuts off the fuel. (10 in the diagram) That is the one that went bad on mine bike, starving the engine for gas. The system (from my understanding) does little to hurt performance, and removing it will not gain anything, except a more reliable bike.

    Hope this helps. Haynes manuals have the same diagram, but easier to see. They also explain it better. Removing the system will eliminate the problem you are having because you now add another tube to vent the tank.

    Also, here is a good procedure to remove it if you want. http://www.webbikeworld.com/Motorcyc...les/pulse-air/

    If you do not have the Haynes manual, let me know and I can copy it and post it here.
    I believe I will remove all that. Set up the fuel feeds to run only one petcock. Take a hard look at the pulse system. Run a new vent line..soon as I have time. Haven't even had the tank off yet.
    Jim Gregory
    92 R100RS
    05 Sportster Roadster

  13. #13
    Benchwrenching PGlaves's Avatar
    Join Date
    Oct 2003
    Location
    "Big Bend" TX
    Posts
    8,659
    Whether the shed system is left in place, or not, the tube the vent hose connects to must be clear. In the case of the OP it probably isn't. My preferred method of cleaning is to work from the bottom with a piece of fairly flexible wire. Old clutch cable works well. Poke, pull, poke, pull, poke, pull, bringing crud out the bottom as you poke and pull.

    Blowing it clear with compressed air also works but that pushes the crud clogging the line into the tank. If you can find the top of that vent tube, then poking from the top down is also an option. BMW did a good job of hiding the vent top though so good luck.
    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://www.bigbend.net/users/glaves

  14. #14
    Registered User JGREGOR1.JG's Avatar
    Join Date
    Nov 2013
    Location
    southern CT, USA
    Posts
    79
    Quote Originally Posted by PGlaves View Post
    Whether the shed system is left in place, or not, the tube the vent hose connects to must be clear. In the case of the OP it probably isn't. My preferred method of cleaning is to work from the bottom with a piece of fairly flexible wire. Old clutch cable works well. Poke, pull, poke, pull, poke, pull, bringing crud out the bottom as you poke and pull.

    Blowing it clear with compressed air also works but that pushes the crud clogging the line into the tank. If you can find the top of that vent tube, then poking from the top down is also an option. BMW did a good job of hiding the vent top though so good luck.
    Now we getting somewhere. Is that tube straight or curved. Most likely curved I would guess.
    Jim Gregory
    92 R100RS
    05 Sportster Roadster

  15. #15
    Registered User JGREGOR1.JG's Avatar
    Join Date
    Nov 2013
    Location
    southern CT, USA
    Posts
    79
    Well I didnt have a chance to remove tank and unclog things yet. Rode to work this morning loostening the damn cap every few minutes to let air in. Rode home after work without issue. (?) drilled a hole in the bottom of the cap turning my "shed" cap into a "non shed" cap. So snowbum says anyway. Hope it works. Wish I had time to fix it right but I just don't.
    Replaced light bulbs in the instrument cluster. Very straightforward. Replaced bulb in the volt meter. NOT easy. The wire was broken off the bulb socket. The brass bit the wire was soldered to, and the bulp center sit's on, was gone. Made a new one with a solder blob and a file. VERY hard to work in that space. But all the lights are on now.
    Got some carb stiks and balanced the carbs.
    Running out of little things to fix. Got some big things though.
    Jim Gregory
    92 R100RS
    05 Sportster Roadster

Posting Permissions

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