Dual-Independent Float Kits
An aftermarket product,
sometimes used on BMW Airhead Motorcycles and other vehicles
Copyright, 2014, R. Fleischer
The MAIN advantage of these kits is that you do not ever
(probably) have to replace the floats. That does NOT apply to the float needles, of which there were two basic types, and the VITON tipped ones have the easy to lose
fine wire clip, same as on the stock carburetors, that insures
positive float needle operation.
If the original floats (which DO AGE) are really bad, and or the float needle bad, things will certainly improve with PROPER installation of these PRICEY kits!...and THOSE are likely the HONEST and TRUE reasons that SOME find improvements with these kits!
FIRSTLY: Here is a link to TWO pdf articles on this website. These are actual Bing Bulletins. There is an explanation of how the Bing Dual-Independent Float kit conversions are supposed to work, and how adjusted, according to BING. Please read these Bulletins before reading further in my article.
bing-tech-bulletin-1984.pdf This is the original 1984 dated bulletin describing the new kit.
bing-tech-bulletin.pdf This is what Bing in the USA produced, and if you read it carefully,
it differs a bit from the above bulletin.
The original kits used metal (zinc casting) bowls. Later, Bing began shipping the kit with plastic bowls, of a dark-colored material. Those sometimes developed microscopic cracks, typically vertical-running, and in a corner. Later, Bing went back to zinc bowls. The zinc bowls were rather costly to purchase from Bing if you needed to replace a plastic one (and they stopped making plastic ones). Bing claims mileage increases. That is unlikely, unless you were previously running rich from wrongly adjusted floats; or, are so aggressive that you lean the bike as on a twisty race-course; or, you are doing very aggressive off-roading, with the bike often-times assuming very large angles from vertical. In my opinion, there will be no appreciable mileage increase from normal touring.
Bing ORIGINALLY offered these kits in various types, depending on your carburetor model number. These kits were offered for the slide carburetors as well as the CV carburetors. Kits were numbered #1 through 4 for BMW motorcycles:
#1: type 53 for R50, R60/5, and the /6 carbs.
#2: type for CV carburetors with 4 screws in the top cover.
#3: type for CV carburetors with 2 screws in the top cover.
#4: type for ALL 40 mm carburetors.
Kits #1 and #2 had the square grey float needles, requiring no needle clip.
kits #3 and #4 had the larger, triangular, brass, viton tipped needle with the needle clip.
In the clickable pdf that has a sketch, the 10.5 mm distance, which is 0.413", does not show that the bridge and carburetor base are also PARALLEL. This was added in a much later USA bulletin (which I have).
ALSO, the sketch does not show that the distance is 8.5 mm, which is 0.335", for the model 55 carburetor...not used on the BMW's anyway.
The various types of carburetors are used on vehicles other than BMW motorcycles, so to make this section more complete, know that the 53 carburetor was made in 24-27 mm; the 84 in 28-32, the 54 in 34-40, and the 55 in 40-55. The 64 and 94 were the CV types.
Included in my personal files are original bulletins from 1984, engineering bulletins.
Bing promoted their new float system for transverse to direction engines, and for special industrial engines and ultra-light aircraft, etc., that had special inclination performance requirements.
It is my belief that these kits were developed originally for small aerobatic aircraft, and only later Bing decided it could sell many more, at a handsome profit, to motorcyclists. As noted, I have the original Bing engineering bulletins on these kits, from the early 1980's.
Bing also furnished, through its Bing Agency International in the USA, another bulletin that explained how Bing wanted you to think about the kit's operation, using a glass of liquid as an example, as liquid sloshed back and forth, with acceleration and deceleration, and how, supposedly, this worked on BMW bikes (BUT....remember, our carbs are rearward and angled, NOT a transverse engine!
Bing said that there is a lean-ness, then richness, power changed, and you subconsciously added more throttle to compensate. Take this with a grain of salt!
"My Airhead motorcycle came with the twin independent float conversion... why do the gurus "hate" them? I also would like to know what IS the proper procedure for adjusting the float levels on carbs with this conversion, assuming I am going to do it myself ..." (and other inquiries.....)
I passed on what I knew about this kits as far back as 1984, and I later did articles on these kits, including discussing the original engineering behind their development, which Bing would probably prefer I not post. NOTE that BMW never installed them,... it would hardly have cost them anything...there are several reasons they did not.
Primarily there is the lack of an BOWL "overflow" that has "guru's" most upset. All the stock CV Bing carburetors, as delivered by BMW, have an overflow capability at a vent port on the carburetor body, which is rather high up, This is in addition to the tiny diameter vertical 'overflow' (vent) pipe coming out of the bottom of the bowl. Neither of these may prevent some flow into the left cylinder, especially if the bike is on the side-stand.
Side-stand's vary in their angle which is another factor. There is a danger in trying to start the engine with liquid gasoline in the left cylinder. It does not take a lot of gasoline, as you try to crank the engine, to have what is called a 'liquid' or hydrostatic lock, which, especially if the right cylinder fires; can lead to busted pistons, bent rod, etc. With the Bing independent float kits, there is NO DIRECT BOWL VENT, which acts somewhat as an overflow. You can see this by looking at the Bing bowls in the kit, versus your stock bowl...there is NO vertical tiny pipe in the conversion kit bowls. I will not get into the methods of providing that venting or overflow here.
While I am often considered as one of the so-called "guru's", I actually have nothing too much against use of these Bing Independent Float Kits, or alcohol-proof kits, or however Bing
Agency in the USA advertises and sells them.
Just be sure your petcocks work properly (don't leak internally either) ....and are in the OFF position (horizontal lever position),
if using the side-stand.
Pay attention to my advice to always turn off your petcocks when the engine is off (Bing ALSO cautions this). This is especially important if using the side-stand.
****OFF is NOT "auf"!!!! if your petcocks are so marked.****
You will have to adjust the flimsy kit float bridge a few times, perhaps only twice, but after that, they settle down and are reliable. You will still have to replace the float needle now and then, perhaps 30K-60K intervals.
The twin independent floats in
these kits seem to last forever in any type of gasoline or time and miles (NOT so
the float needle).....but the adjustment brass-looking bridge is
thin, flimsy, and is poorly heat treated.
It is possible that this was done on
purpose, to be fair about this. That
brass-looking bridge needs to be adjusted properly at first
install, and then once or twice
more after being in use for awhile. Bing
says readjust (implying once) after 5 hours, I say this is not enough, and should
be checked again after maybe a month or more, and then maybe at
yearly....or even longer, intervals; typically they are OK after they settle
The float needles in all the CV carburetors were (very early models) a solid metal, and later Viton (or? rubber) tipped, and are now, per Bing, the same part number, no matter if the tip is black, gray, red, etc. The float needles in the Bing dual-independent kits are the same as the stock types. Float needles wear out...and allow overflowing with the kit...and with stock floats too. USUALLY, there is a teeny bit of foreign matter lodged in the float needle seat or on the needle tip. You SHOULD have good hoses from the bottom of the aftermarket gas filter you SHOULD have below the petcocks?...hose insides can deteriorate. Tipped float needles are made of VITON...or were. How they handle alcohol in modern fuels is a good question. SOME forms of VITON are OK in nearly all types of alcohol. MOST Viton material is pretty good in ETHANOL. I have NOT seen any more problems with the kit needle and seats than with stock.
***NOTE! that BMW dealerships generally charge LESS for Bing carburetor parts than Bing Agency does, but the dealerships may not stock the independent float kit parts (as they are not BMW parts)...although the FLOAT needles are the same).
First; here are two scans of some old Bing information. Read them at this point, before proceeding.
CAUTION! If you are not familiar with Bing carburetors, you should know that the thin round metal rod that holds the float bridge to the two carburetor support bosses, goes into the support bosses from only one side. The rod is KNURLED at ONE end. The OTHER end goes in FIRST. When removing the old rod, remove it knurled end first; using a very thin rod at the NON-knurled end, and a very tiny hammer or even the plastic handle of some tool as a light impact tool!!...be GENTLE. You can devise a very thin rod for use as a punch, by grinding a nail, remove sharp end or reshaping it.
Under NO CIRCUMSTANCES put much force on that float rod.
When installing a new rod, tap it in or squeeze it in very gently. Remember: install the NON-knurled end of the rod first....and install into the Knurled end of the boss. That way, the knurled rod end goes into the knurled boss end, lastly.
Be truly careful. You will have a VERY bad day if you break a boss.
Be careful to avoid mis-adjustment of the bridge....it could then cause rubbing, or uneven, even angular, float operation. If you mis-adjust the bridge, you can get all sorts of problems, from flooding to mixture problems. This is NOT a difficult job, just be slow, cautious, careful.
Be careful about the two vertical float pins in each
float bowl....those two pins have been known to be bent, and
need gentle straightening...otherwise the floats might stick at
the bottom (more, later on....).
On the Bing CV carbs, as STOCK, with the die-cast aluminum-looking (probably zinc) float bowls, there are two round holes, in the forward corners of the float bowls. ONE is plugged off, with the opposite one similarly plugged for the other carburetor, as there are left side and right side bowls. The one NOT plugged off is a 'well', with a small brass jet at the very bottom. That jet, on the stock or kit bowls, SHOULD be checked for not being clogged. The well is where the main body of the carburetor has a small tube that dips down into the well. This is where the enrichener (mis-named choke) gets its fuel. Check the tube to be sure it is OK. On rare occasions folks have had carburetors with water in them and if the water freezes, the tube can split, and then you must repair that damage, with a sleeve.
The Bing "alcohol-proof" kits that have PLASTIC BOWLS (that I have seen so far) do NOT have any corners plugged, but the jet is in only ONE of the wells. In fact, many Bing kits were furnished with the jet in a baggy, UNinstalled. That was so YOU could install the jet in the correct corner.
YOUR newly acquired bike with the kits, already should have the jet properly installed, one would hope, at the correct corner...do check that. Especially check this because as I noted, Bing shipped some kit bowls with NEITHER corner plugged off. The proper corner FOR THE JET is the one that mates to the DOWNward pipe coming from the carburetor body corner. If the jet is not properly installed in the Bing Dual Independent kit, the 'choke' (enrichener) will not work correctly. In the stock metal bowls, you cannot fit the wrong left or right bowl due to the plug. If a dual-independent Bing bowl was installed with the jet not in the proper corner, the bike would start OK, I think. But, this would allow a greatly over-rich choke (enrichener) action during the warm-up period. The jet is there to fill the 'well' in a controlled way, so that a very rich initial STARTING mixture is possible....and after approximately 15 seconds of running, the bowl is supplied by the quantity allowed by the JET. Thus, a jet not in the correct corner could allow some washing down of the cylinder walls with lots of fuel over too many seconds of operation .... not so nice. So, the thing here is, DO NOT install the wrong bowl at left or right; be sure the jet is in the proper corner. EASY to see which goes where....the carburetor has a very tiny thin diameter pipe, going downwards,,,,,it must go into the JETTED unplugged bowl corner. The tiny thin diameter pipe, or tube, must be in good shape. You may see a tiny side hole in it, which is normal.
All of the metal dual-independent bowls I have personally seen have the jets already mounted in the corner, properly. If you order a bowl, you are going to get the metal one; there is a LEFT and a RIGHT.
If the float guide pins are bent, the floats can hang up! I have also seen some floats with poorly peened tubes in the float itself.
Here are some hints from my own work on these:
1. Bowl CENTER to top of gasoline, ~1-5/32". This is APPROXIMATE & is for 40 mm carbs.
2. Carb is supposed to be upside down for the original installation instructions. If adjustment is checked and done with carburetor on the engine, which is fine for future checks, the lower part of the spring-loaded plunger type needle, that is, the plunger itself, must be such that the plunger is JUST being touched/pressured, but the plunger has not moved upwards yet, for both the parallel and distance measurement. For the BMW's, that is 0.413". Excessive pressure will depress the needle plunger and give a false reading. This measurement can be done by holding a flat wide steel rule against the lower part of the carb body and using another narrower rule marked at 0.413" MINUS the wider rule thickness, vertically from that, noting, using fingertip and hardly the slightest pressure on the bridge, where the bottom of the bridge finger (either) is parallel and the measurement is correct. This is a pretty accurate adjustment point, rather better than #1, which can be used, with 'QUICK' bowl removal, as a double-check on your work. Better is on the workbench, but NOT necessary.
3. Hairclip is not used at float bridge tang area on 64-32/1 through 20.
4. The spring loaded plunger type of float needle has a tiny hole in the bottom. That hole, the bridge tab,
are mechanically coupled by a very easy-to-loose teensy wire clip. The purpose is to make for very
positive opening of the needle port. Assembly of the needle, clip, & float bridge are best done on the
workbench, on a piece of old white bed sheet. YOU CAN do it on the bike, if careful...and do put a
sheet on the floor! I always stock extra wire clips.
I will assume the new twin independent floats kits were properly installed:
If the carburetor is OFF the bike:
First, turn the carburetor upside down. Adjust the tab on the bridge piece and the arms themselves, so
the arms are parallel to the carburetor base and even with each other. Use a very small screwdriver,
very carefully, to adjust the tab. The arms must also be parallel with the carburetor base and
also the two arms parallel to each other. This condition must exist in future checks too. The
distance per the Bing sketch of 10.5 mm (0.413") must exist.
If the carburetor is ON the bike:
You have to lift the arm assembly very VERY gently with a fingertip, and NOT ..NOT!....allowing the
spring loaded plunger (if you have that type) in the float needle to be more than just barely touched.
You CAN feel the resistance though...just do NOT depress the needle plunger. Same adjustment(s)
are to be done.
When carburetor is ON the bike, that above adjustment MAY be easier for you to do by observing the point gas just stops or just starts flowing....that is the parallel point, or, should be.
The part of the arm to look
at for the parallel-ness is the BOTTOM of the arm, as viewed as if the carburetor was ON the bike. BOTH arms must be equal and parallel.
When using the small screwdriver, you bend the tab against the steel retaining pin. You will see what I mean when you try to figure out how to bend the tab. DO NOT BE HAM-FISTED.
Note: A little known problem with the individual independent floats themselves is that there really is a top and bottom to SOME of them. Bing ignores this. Because of the tight fit at the bottom combined with the slight upward slope (and very close to the bowl rod) of the bottom of the 'new' float bowls, the floats CAN, sometimes, 'stick', to the bottom of the bowl. They can also stick at the bottom if the pin is bent even slightly!! Usually, but NOT always, this 'potential problem' does not cause a problem due to the motorcycle vibration during operation.
I suggest you be careful to install
the floats on straight up pins. Another thing to watch for is that the center metal
pipe area (that is part of the float itself) is such that the
broad-rivet head of that pipe is DOWNWARDS, towards the bottom of the bowl. It is possible to actually 'feel' this float grabbing at the bottom, especially if the rounded larger head area is up (or pin bent), instead of properly down...which raises the floats very slightly off the floor of the float bowl. I had one bowl that I saw that this was exceptionally poor....so I installed the floats rivet pipe head
downward, and I put a very small and very thin washer over the bowl's
bing-tech-bulletin.pdf has a sketch, near the bottom of the page, of the float bridge adjustment with the carburetor on the workbench, upside down. The RIGHT end of the arms (the two arm ends MUST be parallel) have a wider area on the right-most part of those arms. You could describe it as wider by a small amount. The UPPER surface of that wider part must be not only be parallel to the carb base body, and both arms even to each other....but the DISTANCE from this upper surface arm part to the carburetor base must be 10.5 mm...which is 0.412 inch. This covers all the CV carb models used on our Airheads...there is a different specification for ONE model of Bing not used on the Airheads....it is listed on the sketch above, for model 55 carburetors, where the distance is 8.5 mm.
After some hours of use, reset the bridge if needed, at the least do check it. The bridge will change its adjustment slightly due to its heat treatment (I THINK),....and some settling-in of the tip of the float needle.....and teeny changes in the internal float needle spring parts, etc. You will probably do this with the carburetors attached to the motorcycle, rather than remove them to the workbench. Mind my previous comments on how to do this with the carburetor ON THE BIKE.
NOTE that you WILL have to change the float needle now and then, perhaps at 30,000 mile intervals, and rechecking adjustment is mandatory at that time...same as a stock carburetor. The adjustment of these twin independent float kit units is slightly more time consuming than the simple adjustment method of the stock floats.
The lifting of the float bridge to see the exact contacting of the float needle pin plunger end is tricky. Certainly, no matter how done, you must be VERY gentle with the fingertip....to see the correct adjustment.....and to NOT distort the brass bridge. It might be a lot easier for you to turn the gas on and lift VERY gently to the point the gas JUST shuts off, then lower your finger to the point the gas JUST starts flowing. That is the parallel point....or should be. Be careful with that bridge. It is flimsy, and if you lift at one arm with any real pressure, you can distort it.....and both arms must remain parallel to each other, as well as the final adjustment being parallel to the carb. body.
This is UNOFFICIAL: Once in operation, one could turn off the fuel, remove a bowl quickly to avoid excessive fuel getting into the bowl, and the bottom of the BOWL CENTER AREA to the top of the fuel should be very close to 1-5/32". This was for a 40 mm Bing CV carburetor. I have not checked a 32 mm. When I do, will post it here.
02/18/2005: Clarifications and final release
05/22/2005: Add extensive notes, yellow background
05/24/2005: add 4 scanned pages, modify descriptions, minor other things
08/24/2005: Go over article and clarify some details
06/24/2007: Edit the article for clarity, add more cautions.
01/10/2008: Rechecked article
04/13/2009: fix very minor typos and clarified a couple of details
09/13/2009: Correct typo in ...OK.... pay attention here!::: area, where I had 19.5 mm instead of
proper 10.5 mm.
05/17/2011: slight cleanup. Still a very messy article!
09/19/2012: Add QR code and update google code and fix a couple of unimportant spelling typos
04/30/2013: Complete re-do of the article. Add two bulletins, remove one, re-arrange article,
clarify certain details, etc.
05/13/2013: Add the Bing 1984 original bulletin bing-tech-bulletin-1984.pdf
05/14/2013: Clear up a minor confusing point.
02/08/2014: Revise in several areas, to avoid some confusion with statements about the bowls; clear up typos;
remove information on the bowl gasket that could cause confusion, etc.
Copyright, 2014, R. Fleischer
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