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Thread: HI YALL, Possible carb problems

  1. #1
    Registered User mag00's Avatar
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    HI YALL, Possible carb problems

    I was just wandering the net looking for saddle bag covers when I decided to come to the MOA page. Then I noticed the forums looked pretty cool so I signed up. Gotta love the high tech.

    Here's a brief overview of my problem. 91 R100GS. Hard starting when cold. 33 mpg. Idles to me rough. Pops sometimes on left bank. Chokes out coming to a stop when cold. Runs fine on highway, but under load seems to vibrate excessive.

    I've taken it to two separate dealers and it is somewhat better,(it idles now) but still isn't right. Compression is 150 on both jugs and the valves were trippled checked. Float bowls have been cleaned etc. Throttle cables lubed etc. Timing was checked thrice also, but I find it to be a degree off, dealer say it's fine.

    Anyway I would like all your help in diagnosing finding parts and repairing this myself. I'm just tired of shelling out the bucks and not having my beemer run right.

    All help will be appreciated.
    Dave
    91 R100GS Bumblebee

    http://davesbmw.com

  2. #2
    Don't forget your towel
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    You didn't say what kind of work your trips to the dealer involved, so I'll just jump right in at the begining.


    Part of the beauty of the airhead line is how simple they are to work on. Get yourself a Clymer and a Haynes manual (they attack the same job from slightly different angles, it's nice to be able get a second opinion with out leaving the garage) read up on basic tune-up procedures and get to work.

    After 13 years you are probably well past due for a good carb cleaning and subsequent re-balancing. At the very least, pull the main jets and get them cleaned out, they get gummed up pretty good. Also check the air filter.

    Steve

  3. #3
    Registered User mag00's Avatar
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    Originally posted by sgborgstrom
    You didn't say what kind of work your trips to the dealer involved, so I'll just jump right in at the begining.
    Obviously not much, otherwise it would run good as requested them to fix when I took it in. Other than lubing the cables. (which I didn't think to do)

    Part of the beauty of the airhead line is how simple they are to work on. Get yourself a Clymer and a Haynes manual (they attack the same job from slightly different angles, it's nice to be able get a second opinion with out leaving the garage) read up on basic tune-up procedures and get to work.

    After 13 years you are probably well past due for a good carb cleaning and subsequent re-balancing. At the very least, pull the main jets and get them cleaned out, they get gummed up pretty good. Also check the air filter.

    Steve
    When I purchased this fine machine, in Colorado, the first thing I did when I got it back to CA was to go over it doing all maintanance etc. All fluid were changed new filters, greased the stearing head, polished and cleaned like any conscientious beemer owner would do.

    It never would idle down and at time would run ok but other times coming to a light would idle high and rough. Also had a blown out gasket in the exhaust connections at the downpipes.

    So I figure what the heck I'll just take it to the BMW dealer, they work on these all day long and should be able to fix her right up.

    Boy was I wrong $300 later I still had the exhaust leak and it wouldn't idle, the two things I brought it in for. The service writer said that all that would be covered on the service. What a liar. Then when confronted about why it ran like crap and still had the exhaust leak, "well it must be something more involved lets keep it for a week and figure it out." Thankfully my ride had left and the bike was my only way home. I then took it to another BMW dealer and they at least were able to diagnose the sticky throttle cable, so now it will idle.

    The idle is somewhat strained. Like it runs on one and half heartely on the other. Like it wants to fire properly but just can't. Today it was much worse.

    I was on the Bing website and they sell and upgrade kit. Is this kit an improvement over stock? They claim better fuel efficiency. This is probably where I am inclined to spend my next money, that and a saddle bag.

    For what I've already spent on dealer repair work I could have bought new carbs.

    How bullet proof is the ignition on the 91 r bikes? I'm pretty sure it is a carb problem, not just a simple adjust, as I or two dealers can't get it dialed proper. Considering I used to tune my Kawi H2 tripple, I don't see how two jugs could be so troubling.

    The carbs have been off and cleaned and inpected by me, and only one thing seems to give me concern. The left carb seems to have some visible scratches in the slider. Not enough to hurt but maybe. All connections etc, tight and free of vacuum leaks. I've tried different blends and octane gas. Today it would idle on one only. the right bank. I always use the center stand for longer parking.

    Any HelP? Hints? IdEas?
    Dave
    91 R100GS Bumblebee

    http://davesbmw.com

  4. #4
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    neutral switch

    Sounds like you have the problem figured out. My push rod tube seals leaked to the point and blew back around my neural switch to the point that I thought I had a seperate leak. Still waiting for parts to fix that problem. Take care

  5. #5
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    whoops this was suppose to go to the neutral switch problem...Darn computer: My screen has been locking up and doing weird things. Wish I was a computer guru!

  6. #6
    Focused kbasa's Avatar
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    Just a thought here. You bought the bike in Colorado, which is, I presume, well above sea level and took it to CA, where I presume you're at something closer to sea level. Did the previous owner rejet the bike to run at altitude?
    Dave Swider
    Marin County, CA

    Some bikes. Some with motors, some without.

  7. #7
    Registered User mag00's Avatar
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    Thanks, now there's a thought. The guy I bought it from told me it originally came from California so I didn't consider the rejet, if it was done. At least now I have a good reason to go back in and fix things.
    After being to the dealers twice and them and their high tech equip, it's hard to justify tinkering, but I haven't tried since the cables been freed up. Maybe I'll have better results.

    Any idea what the sea level jet sizes should be, I still haven't dug up my manual since my move.
    91 R100GS Bumblebee

    http://davesbmw.com

  8. #8

  9. #9
    WesPeterson
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    Originally posted by Mag00

    Any idea what the sea level jet sizes should be, I still haven't dug up my manual since my move.
    My Bing manual says your bike would have carbs 64/32/357-358 and the jet size would be 135. If you want to check your carb numbers, I'll cross reference the manual.

  10. #10
    Don't forget your towel
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    Somebody once told me "90% of all carb problems are electrical"

    That being said, you said you cleaned the carbs, did you also inspect/replace the assorted rubber bits? Diaphragms ok? How about the little o-rings that seal the throttle shaft? Does messing with the idle adjustment screw do anything? Is the "choke" mechanism shutting off? What do the plugs look like (black, brown,grey)? Spark plug cables go bad over time, are they original?

    I'm just working through the assorted angles I'd use to trouble shoot this if it were in front of me.....

    Steve

  11. #11
    Registered User mag00's Avatar
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    Thanks for these grreat tips. I have the 64/32/357+8 carbs. The diaphrams are OK floats seem ok, needle seat ok, didn't check the shaft seals hmmm. Choke disengagine ok, I assume as it seems to do better with a partial choke---leads back to shaft seals hmmm. Spark plug wires? Cheap enough, that will go on the order list. Spark plugs are new, I'll check again, but seemed no odd stuff.

    Also the other day while idling I did a quick check by pulling on the throttle cable at the left carb while idling. The left bank starts to fire and the r's go too high for idle. I sortof trust that the carbs have been syncronized properly, Acceleration good through all range, no hesitation etc. Runs well on the highway.
    Last edited by Mag00; 04-17-2004 at 05:11 AM.
    91 R100GS Bumblebee

    http://davesbmw.com

  12. #12
    Registered User jgr451's Avatar
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    Speaking of scratching our heads over carb performance,what is the experience out there of buying the replacement(expensive)floats vs.the longevity of the originals?My carb ocassionally floods and I am thinking it is the floats saturated..84 R100 .

    Sorry,not meaning to hijack this thread but to widen the discussion at hand!!



  13. #13
    Has the GS-Lust The_Veg's Avatar
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    The w6rec websitre mentioned in the list of online resources belongs to a chap named Duane Ausherman who was once the BMW dealer for the San Francisco area. Excellent info he has, although it is derived from knowledge of bikes up to the /5- after those he kind of lost interest, but is still interested in helping those who need to learn. You can talk with him and many other good helpful folks at www.boxerworks.com , a site at which I have really enjoyed being part of the forum community for about three years. it's as unmoderated as it gets and the humour runs way loose at times, but the folks there are very helpful and Airheads are what they talk about.
    Good luck and keep us posted!
    2012 R1200GS

    "If you can't fix it with a hammer, it's electrical." -somebody's dad

  14. #14
    WesPeterson
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    Originally posted by jgr451
    Speaking of scratching our heads over carb performance,what is the experience out there of buying the replacement(expensive)floats vs.the longevity of the originals?My carb ocassionally floods and I am thinking it is the floats saturated..84 R100 .

    Sorry,not meaning to hijack this thread but to widen the discussion at hand!!


    I don't have any direct experience but if you read

    http://home.jps.net/~snowbum/bingcv.htm

    there is a discussion of the Bing alcohol proof floats (the more expensive ones) and a recommendation against purchasing them. I offer this FWIW and with no personal opinion.

  15. #15
    Registered User jgr451's Avatar
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    Wow!!Some detailed article!!
    Thanks for the tip.

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