sealing cork gasket to bing float bowl?

Discussion in 'Airheads' started by hotwheels22, Mar 13, 2018.

  1. hotwheels22

    hotwheels22 motorradRP

    Joined:
    May 29, 2015
    Oddometer:
    4,008
    Location:
    austin
    my bings are pissing me off (literally) and i’ve been ignoring it and using the shutoff valve. keeps it sort of under control.

    before i crawl back under there (with my safety glasses) and clean everything up, inspect and then reinstall the float bowl (by staring up at a bing carb and a tank full of fuel...).

    anyone sealed their cork gaskets to the float bowl overnight so you are /sure/ they are seated?!

    these things seem like they last a very long time and the minor aggravation of removing them would be offset by knowing for sure that they are fully seated.

    also, has there ever been a case where the castings at this “bowl to body” intersection is just a bad fit with some extra cast material or something? i suppose i could switch float from left to right. it’s currently the left carb but seems to happen i the centerstand as well. i will also be checking for dirt and all the usual suspects while i am there...

    THANKS
    #1
  2. Disston

    Disston ShadeTreeExpert

    Joined:
    Aug 31, 2009
    Oddometer:
    14,413
    Location:
    Silver Spring, Md
    I don't think the float bowls swap side to side. Forget what it is, they do look like they swap, but it's something to do with the brass tubes. Go ahead and try it. You'll see.

    You are supposed to use the petcocks and shut them off when stopping the engine. The floats or needles can fail and if the petcocks aren't used, as designed, the engine can fill with fuel which can hydrolock next time the starter is used.

    The Bing float bowl gasket is very robust and works very well but they don't last forever, nothing does. If you are getting fuel dripping while the engine is running it sounds like the floats need adjustment. If you get fuel leaking after the engine is stopped and leaving a spot on the floor you may need a new gasket. Adding sealant like RTV has never been popular and I think it's unneeded when the system is working as designed but as a temporary measure till new gaskets arrive maybe would be seen as justifiable.

    Worn or damaged float needles can cause the floats to not turn off the flow. Debris caught at the point the needle works can cause the flow to not be turned off.
    #2
    hotwheels22, rwiles and ccmickelson like this.
  3. hotwheels22

    hotwheels22 motorradRP

    Joined:
    May 29, 2015
    Oddometer:
    4,008
    Location:
    austin
    yeah. thanks. i should have been a lot better at turning off the petcocks than i have been. i also forgot about the handedness. it’s the capped well (is that what causes the handedness...?)?

    anyway, this carb is a mess. not necessarily running (don’t see nothing on my boots) but almost always in sitting even if it is a short period of time.

    mostly i don’t want to be under there staring up at the carb trying to make sure the cork gets fully seated hoping nothing drops into my eyes. i’d love to just use some temp sealer on the bowl/gasket and just slap that puppy on...
    #3
  4. Disston

    Disston ShadeTreeExpert

    Joined:
    Aug 31, 2009
    Oddometer:
    14,413
    Location:
    Silver Spring, Md
    The cork gaskets fit in between ridges and stay in place rather nicely. I could install the float bowls with a blind fold on if needed.
    #4
  5. nk14zp

    nk14zp Long timer

    Joined:
    Feb 24, 2010
    Oddometer:
    1,454
    Location:
    Maine
    If you do decide to use sealer I have had good luck using weather strip adhesive on cork gaskets. Just ONE side of the gasket.
    #5
    hotwheels22 likes this.
  6. hotwheels22

    hotwheels22 motorradRP

    Joined:
    May 29, 2015
    Oddometer:
    4,008
    Location:
    austin
    yes, that’s why you’re called the shade tree expert...
    #6
  7. 190e

    190e Long timer

    Joined:
    Feb 20, 2013
    Oddometer:
    1,734
    Location:
    England
    That's my experience also. 12 years ago my bike came with some spare float bowls gaskets. The bowls have been off dozens of times but I've never needed to use them.
    #7
    black knight and hotwheels22 like this.
  8. hotwheels22

    hotwheels22 motorradRP

    Joined:
    May 29, 2015
    Oddometer:
    4,008
    Location:
    austin
    mine never seem to come off flat and are usually deformed in some way. new ones never seem to lay flat in the groove and when i get it up against the body something usually gets bumped loose. so i’m usually on my back staring up at the carb trying to make sure the round area around the enrichener pipe and at the corners is seated properly...
    #8
  9. Jim Day

    Jim Day full manic mechanic

    Joined:
    Mar 14, 2012
    Oddometer:
    3,985
    Location:
    So. Cal.
    Sounds like you have a few problems. Are you suggesting it's leaking fuel while sitting overnight?

    I generally find that leaking float bowels are almost always due to a float needle not seating, but if your petcocks are off at night and it still leaks then you need a petcock rebuild. Count your blessings if a petcock is seeping, and your needle is not seated, and it leaks at the float bowel gasket, that's a mess but it beats the hell out of it filling to the point it leaks down the intake past the valve into the head and then having the gas slip past the rings down into your sump where it will contaminate your oil.
    #9
  10. hotwheels22

    hotwheels22 motorradRP

    Joined:
    May 29, 2015
    Oddometer:
    4,008
    Location:
    austin
    yeah, i got to get in there. thanks. just kind of wanted to eliminate the cork as an issue. fuel will leak if i leave the petcok on (for any period of time really) and i wind up with a drop or two. if i leave it on longer it will accumulate.

    there’s some weird GS specific stuff in snowbum about having the correct hose at the carb (foaming) and vibration at road speeds. starting to wonder if knobbies or taking speed bumps at speed could be getting my cork wet - or something...

    http://bmwmotorcycletech.info/Carburetors-that-piss.htm

    Attached Files:

    #10
    Jim Day likes this.
  11. hotwheels22

    hotwheels22 motorradRP

    Joined:
    May 29, 2015
    Oddometer:
    4,008
    Location:
    austin
    hi jim,
    thanks to all on this.
    i have to admit i initially didn’t realize the possibility of gas getting into the combustion chamber or past the rings. i guess if the bowl fills all the way up that big tank of gas can flow fuel down into the venturi (faster than it can exit the overflow pipe) and it can then flow into the chamber? even worse is if it is on the sidestand.
    i just did an oil and filter change and have the old oil. can i just ask you - this would be /very/ evident in the old oil is that right?
    i am still sort of leaning toward sealing the cork to the bowl so if it does get wet at least it will stay in place and not deform (and possibly also rule out a leak at the cork). but i gather you are indicating that this is really a double edged sword and it may in fact be the lesser of two evils...?
    i realize i am probably just repeating what’s been said but before i try something like this i’d prefer to have the advice...

    THANKS

    <edit: reread jim’s post. i guess he is talking about a leaky petcock which does not seem to be the issue here. so maybe no harm in sealing the cork...>
    #11
    Jim Day likes this.
  12. globalt38

    globalt38 "A Fist Full of Throttle"

    Joined:
    Apr 10, 2013
    Oddometer:
    1,854
    Location:
    Atlanta
    I assume you've checked the gasket for crimping/damage Jon?
    #12
  13. hotwheels22

    hotwheels22 motorradRP

    Joined:
    May 29, 2015
    Oddometer:
    4,008
    Location:
    austin
    thanks. gonna pull it. figured i’d get things together and clean it up and do everything all at once. will report. i still do like the idea of sealing the gasket to the bowl tho...
    #13
  14. thetubespoke

    thetubespoke Been here awhile

    Joined:
    Dec 28, 2014
    Oddometer:
    656
    Location:
    San Antonio, Texas
    Have you checked if the fuel valve is shutting it off? Just pull the bowl off, hold up the floats, and turn on the fuel. Nothing should leak while you are holding it roughly parallel or higher.
    #14
  15. hotwheels22

    hotwheels22 motorradRP

    Joined:
    May 29, 2015
    Oddometer:
    4,008
    Location:
    austin
    thanks man. i need to do this. every time i’ve checked this it shuts off at parallel to the bottom of the carb body. course i could be wrong this time which will be embarrassing.

    i’ve got good screens and basically new petcocks. tank seems fine. can i ask how often this crud in the float needle generally happens? i mean you basically drop the bowl and check it shuts off and your done, yes?

    also, do you have any idea what ‘bum means below when he says you can try to “raising” the float bowl fuel level by 2 or 3 mm (fifth or sixth sentence in)? i thought he was talking about leaks here (and i could try gettting the fuel to shut off /earlier/) but writing this i see maybe in this case he is talking about stumbling due to foaming so you raise the fuel level i guess...?

    apologies for the long quote but it was hard to pull it out and give the “context” (lol).



    In the mid-eighties, BMW made a change to the hose that couples the carburetors to the cylinder head intake stub. BMW softened the rubber compound of the hose. Only 32 mm carburetor bikes went to the USA. They had 13 72 1 338 360hoses. I suggest replacing them with the older style of hose, which was 13 72 1 254 654. You can also try raising the float bowl fuel level by 2 or 3 mm, which applies to both sizes of carburetors. The Euro 40 mm carburetored bikes had 13 72 1 338 362 hoses and I suggest you change them to 13 72 1 264 392. The true story of this hose change is not all that clear, not even when reading BMW's bulletin on the subject. Supposedly the problem was first found on the R100GS/PD. I guess that the problem was then found on the R80GS. In any event, two things happened. First, vibration, road shocks, whatever, could cause the float bowl to overflow. BMW also found that there was foaming & frothing of the fuel in the bowl. So, BMW changed to a softer compound in the hose. NOTE that it is NOT easy to test both types of hose with your hand and find out which is which (you should look at the printed number on the hose!).
    #15
  16. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

    Joined:
    Nov 16, 2006
    Oddometer:
    6,237
    Location:
    Bowling Green, Ky
    most leaks in my experience are from the float needle being worn, dirt lodged between the needle and seat or incorrect float level. but 1st make sure the petcock shuts fuel flow off completely. and of course a torn or crimped float bowl gasket.

    IMHO-use of any sort of sealant is begging for trouble...
    #16
    KatCon85, bmwrench and hotwheels22 like this.
  17. Warin

    Warin Retired

    Joined:
    Aug 30, 2012
    Oddometer:
    5,006
    RTV goes to gunk in gas.. don't even think about using it anywhere in the raw gas supply line.

    ---------------------
    Sealing the gasket on one side keeps it in place, but leaves one face 'unsealed'.
    With these bing carbies the gasket stays in place.. so there is no need for a sealant.
    BMW nor Bing specify a sealant .. so it is not required.
    Using sealant is covering up the real problem.
    #17
    black knight and hotwheels22 like this.
  18. ME 109

    ME 109 Long timer

    Joined:
    Jun 25, 2009
    Oddometer:
    7,084
    Location:
    Albury Australia
    Use a light smear of grease on the carb side of the gasket to hold it in place.
    No sealant.
    #18
    WooPig and hotwheels22 like this.
  19. rwiles

    rwiles Been here awhile

    Joined:
    Jan 5, 2006
    Oddometer:
    342
    Use a new cork gasket. Carefully infuse the cork with wheel bearing grease. Work it in with fingers and take care not to tear the gasket.

    Install the gasket into the carb body channel. The grease will hold it in the channel. Work it in with a finger, all around. Install float bowl carefully.

    The gaskets will likely stay and not fall off when the bowl is removed, and they will not leak, and will last for a long time.
    #19
    hotwheels22 likes this.
  20. UnclePete

    UnclePete Been here awhile

    Joined:
    Nov 13, 2014
    Oddometer:
    741
    Location:
    Plumas County , CA
    Holding the floats up to check if the fuel shuts off will eliminate the needle and seat , but if the floats are too heavy to reach that point once immersed , fuel will overflow .
    The floats may be sinking , or they may simply be too heavy . Check the weight of the floats after they have been immersed in gas for a long time , not after they have been dry on a shelf waiting for the carbs to be rebuilt ...... or measure fuel level in carb .
    #20
    bmwrench and hotwheels22 like this.