Bing CV Carburetors, Part 1 of 2 parts
There is no specific article on this website for Airhead "slide-only" carburetors; only the articles for the "CV" carburetors.
2014, R. Fleischer
basic mini-overhaul can be done with the carburetors in
place on the engine.
Quite frankly, this is often
READ Article #6 on the R75/5
carbs....some really IS pertinent to all the CV carbs:
READ: http://bmwmotorcycletech.info/bingcv-2.htm That is Part 2 of the article you are reading now.
READ: http://bmwmotorcycletech.info/bing-floats.htm That is all about the STOCK floats.
READ: http://bmwmotorcycletech.info/bingindependent.htm That is all about Bing's "Alcohol-proof" float Kits.
For a well-done overhaul article...step by step...with 44
pictures....see BMWMOA magazine, BMW-ON (BMW Owners News),
for March 2003, for an article...in great depth...by Gary
L. Smith. You can probably get that back issue
From that main page, click on left side for Country
Store, and then on the Country Store page, go to Back
I have SOME nitpicking on that article:
1. See my notes in the article you are reading.
2. Use faint amount of silicone grease on all O-rings
and on enrichener parts (do NOT overdo this, you do NOT
want to plug jet holes).
3. If doing a complete overhaul, which involves
removing the butterfly to replace the throttle shaft O-ring
(be sure to silicone grease that one
and be SURE to MARK
the butterfly for correct refitting: something like
TOP, OUTER; or TOP, facing REAR...or something of that
sort....BEFORE you remove the old one. You can hope that the previous workman did not install yours backwards, because it can be
fun to figure out unless you know what it is supposed to look like. I ADDED, in the article you are now reading, on 05/14/2012, photos
of what it IS supposed to look like, and NOT look like.
4. The article you are reading, below, has a LOT more
complete information about orienting the enrichener parts.
Below is a website in which you can enter your carburetor
model number, and get a chart showing all the component
The Bing CV carburetors are moderately complicated in HOW THEY WORK. BUT, there are only a moderate number of places in these carburetors where you probably could run into trouble in working on them. For the 'Newbie', I advise reading all of the carburetor articles completely through, even though you will not likely understand everything at first read. Once you have overhauled your first Bing CV carburetor, you will probably wonder what all the fuss was about.
NOTE: The float needle tips
tend to get faint grooves in them after a lot of miles and if a rubber-tipped type
the tip "rubber" material gets slightly harder, and gasoline tends to slowly (modern gasohol especially)
deteriorate them, and then the needle
tip does not seal well, causing the bowl to overflow onto
your foot. This can also happen if a TEENY MICROSCOPIC particle
of dirt gets into that float tip and mating seat area.....and
also if the float deteriorates enough. The
stock float and float needle probably should be replaced
every 30,000 miles. It is VERY common to see a carburetor overflowing onto your boot. Most Airhead owners have had the problem at one time or another. The fast fix is to turn off the fuel petcock(s), remove a bowl, and jiggle the float up and down with the fuel ON, to flush out any particulate matter in the float needle-seat area. It is important to keep the fuel tank clean, and as the tank ages, the interior reddish-brown lining deteriorates, clogs screens, etc. The rubber fuel hoses also deteriorate INternally, allowing teensy bits of rubber material into the carburetors, where they can cause float needle hangups, as well as plugging the idle or main jet. Use of aftermarket fuel filter(s) below the petcocks is almost a necessity now, with the aging bikes. Information on screens, filters, updates, etc., is elsewhere's on this website.
NOTE: Except for the earliest carburetors with no plunger on the float needle (no rubber tip on the needle either), if you accidentally left the teeny wire clip off the float needle and float, the chances are that the float system will work just as it is supposed to. You COULD, however, have a situation where the needle ‘stuck’ to the needle seat, and no gas flowed, that is one of the reasons why that wire clip was added to later carburetors. FYI, I used to purchase these wire clips about a dozen at a time, and I used to need one every few months when I had the shop. It is ever so easy to have one flip someplace while trying to install or remove to a new needle, and once they 'go someplace', they are near impossible to find. I used a 3 power magnifier on my eyeglasses, and always did the work on a piece of old white bed sheet! I tried magnets, some help, sometimes not.
On the EARLIEST carbs, the needle was all-metal. Bing had some problems and made several changes, approximately at the same time. The needle was changed to some sort of rubber-tipped type; the needle lower end was drilled, the needle got an internal spring loaded-plunger with a teeny hole at the bottom end, on the side, and the tiny wire clip was installed. Besides what was mentioned earlier, I ALSO believe that Bing incorporated the spring loaded plunger so that the fuel level sensing was more accurate, and so the needle would wear LESS, as less pressure was needed to close the orifice off, but more was available. That is, the LEVERAGE is such that as the fuel level rises, the pressure on the seat increases rapidly, compared to a very small fuel level increase. This is difficult to see, and a nerdy point anyway.
I also believe that as the plunger tip wears, which it does and the wear shows as a ring, the needle, being loose-enough in the vertical well area it fits up into, could cant sideways a bit. That MIGHT allow the grooved fuel shutoff needle to hang-up ever so slightly in the SEAT. Since only the needle weight, plus weight of fuel, and maybe vibration, etc., was going to be moving the needle downwards to let fuel in, Bing incorporated the clip, so as the float assembly went down as fuel level dropped, the float assembly positively pulled the needle off the seat.
NOTE: Replacement of a float needle SEAT is rarely needed. Detailed information is here: http://bmwmotorcycletech.info/bingcv-2.htm
Your stock floats are held
into the carburetor by a pin that is knurled on one
end. Pins can wear, although it takes
a VERY LONG time...if yours are worn, replace them. Be
sure to push the pin out in the proper
direction!! A magnifying glass may be needed to see
the knurled end when still assembled. The pin MUST
be pushed OUT with a tiny drift or even a modified nail AT the NON-knurled end.
When reinstalling that pin, this is not
the time to hamfistedly use ViceGrips or Channel-Locks and break the float pin bosses. You install the NON-knurled end first, of course. Except for quite early models, all later floats are tied to the float needle with an
easy to loose very tiny wire clip. That clip is there
to ensure the float needle releases from the
seat, and some other reasons, already discussed. It is a PIA to install the stock
floats...or the KIT bridge...with that wee tiny wire clip
and the float needle. Just takes practice....see
****That clip is not used on the models 64/32/1-20; but it is possible to install them though.
The later float needles lower end has a spring inside and a tiny plunger, and the plunger has a tiny hole in it, that the wire clip fastens to this end part, and the plunger rotates
easily.... some may find it a more than a little bit of an
annoyance reassembling these. When installing the float,
float pin, float needle and that tiny wire clip, they must
be installed as an assembly, a bit tricky, especially if
the carburetor is right side up, but doable. I suggest a
white sheet under the carbs, in case you 'loose' that wire
clip or needle. I highly recommend
that you order SEVERAL of these wire clips when you order
floats and float needles, as they are SO easy to
replace the float needles when replacing the stock
float and vice-versa. When the float needle tip gets bad, the
carburetor will leak
on your foot, the mixture gets very rich, and the mileage
goes way down.
***A very rare problem is a float
needle that seats irregularly, yet a new needle,
sometimes someone even replaces the needle seat, does not
fix the leaking. INSPECT the float tang...it
needs to be flat and NO irregularities in its approximate
center where it contact the bottom of the float needle.
This is very rare since most people have to replace
floats long before this wear is noticeable.
I recommend that the diaphragms be replaced at around
30,000 to 50,000 miles, possibly even 70,000. Some of
this variability has to do with type of fuel, or atmosphere (smog, etc.), and some with time, some with mileage. I have no objection if you let the diaphragms go until they fail by getting a hole or tear in them. You usually must remove the slide and diaphragm assembly and stretch the diaphragm a bit with your fingers, holding it up to the light, to see holes and tears; but sometimes they are very obvious without the removal and stretching. You can purchase the individual parts if you need or want to. Diaphragms seem to hold up reasonably well over time, so I cannot give a
replacement period just for time alone. The type of
components in your gasoline also seem to have some effect
on their longevity. The very earliest /5 diaphragms were replaced by a thicker type, which are all that is
available now. Some of those very early ones might
still be around.
BMW dealers prices are generally
CHEAPER than Bing prices.....and you can NOT depend on
Bing USA parts being of the same quality as the BMW sold
parts. Be careful! .....and do NOT use
Stromberg diaphragms!...except in emergency.
32 mm kits from BMW are 13-11-1-258-051
40 mm kits from BMW are 13-11-1-336-902
There are a number of rubber O-rings used in the Bing CV carburetors. All should come with the rebuild kit (5 O-rings).
These are BMW part numbers:
13-11-1-257-739 Used at the throttle shaft, 6 mm x 2 mm and rather thickish.
13-11-1-257-819 Used at the enrichener shaft, 5 x 1.5 mm and rather thinnish.
13-11-1-257-812 Used at the main jet assembly, 8 x 1.5 mm.
13-11-1-254-735 Used at both the idle adjustment screw and on the idle jet, 3 x 1.75 mm
The screws for the carburetor top cover are M5 x 12 oval head
Except for the /5 models, lighter carburetor springs are available....they are not the same for 32 and 40 mm carburetors. Check with your dealership; or, Ted Porter's Beemershop in California.
There is a type 606 for the 32 mm carburetors that have 3 digit model numbers; a type 908 for the earlier 2 digit 32 mm types, and a type 312 for the 40 mm carbs. Be sure your cables and carburetor levers do not have excessive friction, or these lighter springs will not work properly, that is, the levers will not return all the way, if throttle or enrichener (choke) is moved OFF.
There have been some problems with the R45, R65, and POSSIBLY some of the larger engines, from 1979 or so, for a year or three after that time. The information from the factory on this problem is sketchy. The problem is poor throttle response of various types, during initial starting and riding off, during quite cold temperatures. Basically, the enrichment device in the carburetors is not rich enough. BMW changed the enrichener disc (that disc with the 'funny' holes) by, essentially, enlarging some, blocking off some or adding some. NO change in part number was used. I have the bulletin on it, which, in essence, says to use a new disc, or, modify your disc, by drilling it with specific sized drills, and exactly which/where. I have not posted the SI (are two) on this website, because there are other more likely possibilities for cold starting/running (until the engine has been running a few minutes), such as clogged bowl jet, etc....and, the fact that almost no one rides in such extreme weather, and is not likely to be bothered by a seemingly somewhat slower warm-up period.
Do NOT!!!...use anything but BMW Dealership or Bing Agency furnished BMW diaphragms:
You may run
across articles that say that you can substitute Zenith
Stromberg diaphragms, used on some Volvo's, ETC., for
certain Bing diaphragms. You also may find
that if you do this, they may work OK>>>BUT, MAY work
marginally. There are differences, in
material/thickness that do NOT seem consistent.
The Stromberg CD150 diaphragm
does physically fit the 32 mm Bing CV; and the CD175 does
physically fit the 40 mm Bing CV. DO NOT USE THESE....unless in emergency.
With some Airhead carburetors BMW does
not offer just the diaphragm, and wants you to purchase the
slide with the diaphragm attached. This may
occur with the models where the diaphragm is attached by a
pressed-on nylon ring. If you want to, you can purchase the diaphragm from BINGUSA.
You CAN pry the ring off without breaking it ....if you USE VERY HOT
WATER, EVEN BOILING WATER, to soften and expand the ring. Be gentle, do not try to open the ring too far.
I recommend you
do NOT get carburetor rubber parts from BINGUSA; get them
only from a BMW dealership, they will be correct color
and type of rubber, etc. It would be better if you obtained the diaphragms from BMW dealerships too. BMW dealers prices are generally
CHEAPER than Bing prices.....and you can NOT depend on
Bing USA parts being of the same quality as the BMW sold
parts. Be careful! .....and do NOT use
Stromberg diaphragms! except in emergency. I have a few reports that seem to indicate that Bing themselves, or places that sold them saying they are Bing parts, might have substituted Stromberg diaphragms at times. NO PROOF, yet.
BMW supplies a screwdriver
71-11-1-103-086 in the on-bike tool
kit. Phillips and standard ends,
reversible. The 'Phillips' end is NOT a PosiDrive nor
is it a Reed & Prince tip.
There are better choices, and stronger, longer lasting, but
it is not always easy
to find a screwdriver that is small, and has both phillips
and slot ends, and fits your tools bag for the on-bike
kit. Some folks purchase one of the SnapOn types,
with assorted hardened magnetic tips that fit inside the
handle. If you have the room and budget, the Snap-On
is a QUALITY tool, that NEVER wears out the tips. Be
sure you have the proper size tips...many come only with a
relatively narrow single blade size tip. The proper
Phillips size is #2.
top " phillips" screws are not always really
Phillips screws, they just look that way at a quick first
could be Phillips, OR could be 'Pozi' type.
Someone might even have changed them to allen head types.
The ancient aircraft tip screwdriver called Reed &
Prince works relatively nicely on the PoziDriv screws....as, of course,
does the real Pozi-Drive. The PoziDriv tip is
EXCELLENT for REMOVING the phillips type, if the Phillips
is way tight. Generally install a real Phillips type
with a Phillips screwdriver, but the other types of screwdrivers DO work
better. If the screws are
frozen, you can try a variety of ideas. The Phillips
type of screw was DESIGNED so the TOOL will SLIP after a
certain torque is reached. This is why removing a
stuck Phillips screw is so annoying. Methods of
adding friction for easier removal includes valve grinding compound for a
better grip. For egregious instances, I use a metal block underneath and an Impakt Driver
with the PROPER TIP. Tips for
interchangeable-tip type tools are available from a
variety of sources, including Snap-On, and the PosiDrive
tip IS available.
Some have installed Allen head screws at the carburetor
tops. They are OK, but don't over-tighten, as many of
these have a very small allen and can round-out more
easily. Some early carburetors had common
slot screws. BMW and Bing may be, and have,
shipped EITHER PosiDrive or Phillips screws......be sure that
your 'screwdriver' fits them.
Remove the screws one at a time, coat the threads...and
under head taper...with antiseize....and
replace the screws without too much torque;.....you will appreciate
these hints much later
red plastic-handled screwdriver that is in the BMW on-bike
tool kit, the one with the reversible insert, probably Heyco Germany brand, is NOT NECESSARILY THE CORRECT TOOL
for the carburetor tops....this tool is a
common Phillips, and not a good one. The PosiDrive screws
generally have some radiating lines to indicate they are not Phillips type.
Note, again, that the Pozi type screwdriver will usually work well on
Here are photos of the Posi-Drive screw, and the
screwdriver tip. Note the differences from a
Phillips....the nearly flat bottom in the threads and the
corresponding flat top of the screwdriver; note also the
angles and the extra (lesser) 'splines' in-between the
Many diaphragms have a downward facing tab that fits into a
small recess in the slide itself. Diaphragms have a
somewhat larger downward facing tab that fits in a
corresponding slot in the top of the main carburetor body.
Tabs and slots must
line up during the actual fitting of the parts, and it is
easy to accidentally rotate the diaphragm when putting the
carburetor top back on. When assembling the diaphragms to
the slides, be careful that you assemble things
concentrically and carefully. If the needles are still in
place, be extra careful
not to bend them!!! Tighten the top of the
carburetor screws evenly, coat the threads and underside
with a WEE tab of antiseize, and do NOT overtighten..
With the central jets parts
assembled, some care and wiggling may be necessary to
install the slide and needle assembly in order to get the
needle into the lower brass tube area. NOTE that many
have initially assembled the atomizer jet wrongly. In the
Bing CV carb, that atomizer must
stick UP INTO THE
CARBURETOR THROAT. If you assemble wrongly and then
put a wrench and some force onto the central jet
assembly, you can destroy your carburetor.
The central jet assembly top-most
piece is a tubular brass part with some holes (this item
is called an atomizer). This loose part (as you
begin reassembly) fits directly above the tubular
part called the needle jet. This atomizer must
stick up INTO
the carburetor throat, and only
ONE end of it has the correct
diameter to allow it to fit up
into the throat. A problem can come about
if one has the slide, diaphragm, and its wiggly needle already in place in the carburetor, and you now try
to install the central jet assembly. First, be sure
that the black rubber O-ring on the central jet assembly is
in good condition,... if questionable, replace it, and use
a wee bit of silicon grease to help its installation, AND
on the outside of the O-ring (I also place a WEE bit on the
threads of the jet assembly) so the jet screws upwards
easier. Clean things, including the cavity, first. Regarding the mentioned potential problem: When
installing the atomizer, ETC....be VERY careful that that
the proper end fits into the throat, and that the needle
does not catch the edge of the jet....you might not notice,
and then screw the jet upwards, bending the needle...or
worse yet, applying too much force and breaking the
threaded carburetor boss. NO excessive force is
needed here!!! SO, if the
slide with its needle is already in the carburetor, be
especially careful installing the central jet assembly.
reinstalled into the carburetor clean and dry, and
the lower jet assemblies that the slide needle fits down
into, really should, ideally, ALREADY
be in the carburetor!! If you are careful, see above
paragraphs, you will be OK.
When assembled correctly, the slide, which has two holes at its bottom, off center,
will have those two holes facing the cylinder
head. Slides work OK even when fairly well
worn. Bing has been offering some slides
with O-rings. They are quieter, in a few instances of
Since wrongly assembling and using force with the slide,
needle, and central jet, can damage the carburetor badly, I will get into this a second time, a bit
When you install the main jet, and the parts associated
directly above it, it is best NOT
to install these parts after, BUT
BEFORE you install the slide/needle/diaphragm assembly. Failure to follow this advice can lead to bending the slide needle, you can cause a real hang-up inside, which is hidden from view, and further tightening of the jet assembly using a 10mm wrench can cause you to, in the worst case, split the carburetor boss. This is nasty to fix, most folks just replace the carburetor, or, its body. Some
do an epoxy job, which MAY
or MAY NOT work.
Sometimes a sleeve is made and installed, perhaps epoxied
also. A new carburetor body is REALLY
expensive ...unless you find a cheap wrecked
bike to remove it from. Old hands at working
with Bing CV carbs install any way they want to, as they
know the feel, do it with fingers initially, and also
have their other
hand's finger moving the slide needle at the same time,
typically lifting the slide fully up. This WILL work
well...and is OK for you to do, just be gentle and watch
what you are doing.
Rather often the brass atomizer part
that sticks upwards into the carburetor throat does not
fall downwards and out when the central jet assembly is
removed, or does it later when you are not looking!
Use a toothpick or similar to gently dislodge
it, or a tiny screwdriver carefully on the top side, to push it downwards. It is easy to lose these parts, so do
NOT! Remember, I recommended an old piece of
white sheet under the carburetor if on the bike. Once in
awhile, that brass atomizer part does not seem to want to
go into position...it is usually just a wee bit of crud on
it or in the carburetor body hole. Insert the
atomizer as squarely as you can after cleaning the hole and
atomizer, and it will install OK. Remember that ONE
end is slightly smaller than the other, and only that end
CAN fit. As always, be sure all parts are clean when re-assembling the carburetor.
When one does a mini
field-overhaul on a Bing CV carburetor, it is usually not
necessary to totally disassemble the carburetor, removing
every jet, every O-ring, the enrichener parts, etc. Normally, one really needs only to replace the diaphragm, float, and float needle and spray the passageways a few times with a good cleaner. If you removed the idle mixture screw, replace its O-ring, FAINTLY coating that O-ring
with silicone grease. At some goodly mileage
(Bing says 25K, I say ~60K), one should replace the slide
needle and needle jet. The reason to replace these is
that the needle is designed to vibrate freely, and the two
wear each other and change size, the result of which is a
richer midrange. Yes, cheapskates can lower the slide
needle one notch to sort-of compensate, but even with very
high mileage, this is usually way too
much. Most late model slide needles were aluminum...and the GROOVE wears very fast....they are to be replaced as soon as this is noticed. You can see the wear if the CLIP on the needle allows up and down movement. These types of needles are installed differently and adjusted differently, than earlier needles. Early needles are SLIGHTLY pressured up or down, as desired, and rotated 90°, to find the next 'position'. Later needles have the position set by a special type of C clip, and the needle is held-in-place by a large special screw, that screws down from inside the slide central tube (obviously accessed from the top!). The later type of design is nicer, as you cannot goof on position, but the aluminum needles do not hold up like the steel ones.
HINT: When installing O-rings, put one layer +- of some sort of tape over the sharp threads, and use silicon grease to ease the O-ring into its
groove. Remove the tape afterwards. You can push the O-ring with SMOOTH fingernails on your thumbs, and if you have to, use a tiny SMOOTH dental type of metal hook to lift the O-ring into the proper groove position on the part, or, for the whole operation. This works really well with the idle pilot jet and idle mixture control... and the central jet assembly. DO NOT NICK/CUT THE O-RINGS! I like to smear a VERY FAINT amount of silicon grease onto the O-rings just before I install the part into the carburetor.
One should remove only the necessary
parts, then spray into all the jets (pilot jet, mixture
adjustment hole, bowl jet, central main jet assembly),
etc., with a strong
carburetor spray, and let sit awhile, then spray again in
every direction possible through those holes. I prefer Berryman B-12,
in a version
called 'Carburetor and Choke Cleaner' for this job.
This is a very strong solvent mixture that actually
dissolves most all of the deposits from gasoline, which
many other spray solvents do not. Common brake cleaner spray is BAD, as it is not powerful, in fact it is quite mild for cleaning. You might
consider spraying all the metal pieces, then flush with a
common spray brake cleaner or equivalent. I do
recommend removing the central jet assembly, it tends to
get crudded up, often with 'black' stuff. Be careful,
as has been cautioned above, when replacing. There is an O-ring on it that must be in good condition. Same for idle mixture and idle pilot jet.
Removing the idle mixture screw and spraying
all the idle passageways with that strong Berryman
product is a good idea. Spray three times, waiting a
minute or so each time. Use plain clear silicone grease, or
Dielectric Grease, from your autoparts store... EXCEPTIONALLY LIGHTLY
on anything brass that screws into anything (antiseize is
also OK), and silicone grease for any rubber O-ring.
Use of silicone grease will tend to protect the O-rings
from being damaged when installed, as well as greatly
lengthening their life, and making things turn
keep in mind that there are some VERY SMALL holes in
certain passageways and jets, and you do NOT want grease
I use the silicone grease on the enrichener mechanical parts too, but be careful, you do NOT want the jets clogged. It is helpful on the enrichened shaft, outer part of the disc, etc. FAINTLY...SUPER FAINTLY on that disc, and be careful about WHERE on the disc!
Some Bing carburetors, such as the
R60/6 and R60/7, use an acceleration
jet assembly in the central assembly, these parts all come
out mostly at one time, same as those carburetors
Some carburetors have the diaphragm held in differently. Be
careful expanding any plastic rings/clips, they can crack.
A tad of heat from a
hair dryer, on the plastic retainer, or in very hot water,
NEVER clean jets with tiny drills, etc. There is a
danger here that you might increase its size.
It is probably OK to clear a jet with a very thin wire, but
be careful. Typically a wire is not needed, if spray
solvent is left in place a few moments, and then
"ENRICHENERS"...yes, a whole choking section on this subject:
This section may seem quite complicated at first, it is not. You simply
need to be capable & CAREFUL to assemble the carburetor in the
correct positioning of the parts.
>>Some carburetors were MISMARKED
by the Bing factory<<
ALL will be explained in this section. Read it through
LOOK at YOUR carburetor parts.
A cleaning and
VERY LIGHT silicone grease lubing will make various parts operation smoother. If the rotating
disc, which has holes for jetting, gets plugged (unusual
unless you use grease),
the enrichener won't work correctly. A VERY VERY faint coating of silicon grease is appropriate on the disc; and somewhat more on the shaft and hole the shaft goes through in the cover. Use the grease ONLY where parts are actually making contact. I use a Q-tip to apply it. Again...a miniscule amount.
pieces are easy to mix
up and get installed backwards...or get the left and
right carburetor enrichener parts mixed up. A good rule is to
do both left and right carburetors at the same time. Your
bike could ALREADY have them wrongly assembled!
The enricheners MUST be assembled correctly for
the 'choke' to operate correctly, and to prevent other problems.
In the FLOAT BOWL,
the corner jet in the 'well' must be clean and UNclogged....clogging is a COMMON problem.
There are two very tiny pipes that must be good, and UNSPLIT, one comes down from the carburetor body into the enrichener well of the bowl, the other tiny pipe is in the middle of the bowl, and vents to the underside of the bowl. Once in awhile water collects in the bowl, freezes, and these teeny pipes split. The enrichener pipe may or may not have a tiny round hole in its side.
enrichener parts orientations:
The left side photo, first one below, shows a dot-dimple on the enrichener shaft, which, if correctly marked by the Bing factory and
correctly installed, points to the cable-fastening end of the
lever. Later model carburetors have two slightly different levers plates,
with a notched slot for the cable, & hole for the cable
barrel. I have a photos of them further down this article.
It is possible that some shafts have the DIMPLE REVERSED
by mistake, during assembly of the disc/shaft.
This can happen for the right or the left carburetor. By using my photos, below, of the inside of the assembly, you can be sure your carburetors are correctly assembled, even if miss-marked/miss-assembled by the Bing factory.
NOTE!...it is also possible for the
SHAFT to be wrongly inserted into the disc. Please use all the photos in this article to compare with YOUR carburetor.
The disc on the shaft is spring loaded on
those later models that, pressured lightly with your
fingers, moves the disc in and out on the shaft a tiny bit. Remove the nut, which will
allow the choke lever(s) parts to be removed, first noting how
the lever parts were attached. If you assemble them
wrongly, the cable barrel, etc., will not fit correctly!!!
See a bit further down the page for a more detailed
explanation and photos.
Below two photos: one on RIGHT has shaft market R, and is from
a 1978 Airhead RIGHT side carburetor.
Early carburetors have the
number of tiny disc jet holes
and the elliptical-tail slot different, with
holes missing. There are at least two styles of those.
Although it would be nice to have the dimple, see the left photo
below, such that it
really does point to
cable barrel as designed,
makes no difference,
long as the cover with its parts
fits the carburetor in
correct position. When I find a miss-marked
shaft, I usually grind the dimple down and RE-MARK the shaft!
The correct position, for the RIGHT-SIDE
carburetor, is shown in the
right photo of the two photos immediately below.
NOTE where the elliptical hole, and
the small jet holes, align to the
The lever shown in the left photo is the ONE-PIECE
used on the very early carburetors.
If you were to look at a LEFT carburetor disc and shaft (instead
of the RIGHT, as below), you would see the tail of the
hole pointing the other direction. Photos of the LEFT side are
in this article also, further down after the second set of photos.
NOTE...the right photo should NOT be construed to have
shaft/lever in the position of the left photo.
Left photo is of the early RIGHT side, correctly
type of lever. marked & assembled
SOME shafts are NOT marked correctly, that is, the dot is in wrong place,
180° from correct.
SOME shafts, inside, are stamped wrong for left or right. Mind the photo, above,
it IS CORRECT...AND>>>note the tail of the elliptical hole pointing direction. FYI,
the lever, not seen but a tiny portion faintly at lower right hole edge, is DOWNwards.
NOTE!....there are numerous types of these discs. SOME have a depression for
one or two of the 4 small holes shown in the right photo disc, yet they are not
drilled. The elliptical hole can vary slightly too in size.
Photos of the enrichener with the lever in the two
extremes of positioning are below.
The brass shafts that
operate the enrichener are stamped in the inner ends, L and R for Left and Right carburetors. The stampings can be a bit vague, see above photo on the right. Some late models (well after early /5 CV carburetors) rotating thick metal discs have an elliptical hole, and 4 smaller holes, one of those 4 MAY be a
bit bigger, and some may have one or two blind hole depressions not drilled at all. The holes MUST be clean/clear! There are
numerous types of the discs, some will not be machined
with the elliptical hole through the disc...and different
holes sizes and arrangements and even a special large brass washer plate may be seen, that is, later versions may have a brass thin disc on the other side of the thick disc, it is not shown here.
If you were to have
the LEFT carburetor enrichener unit off the carburetor, and
put it in front of you, upside down...that is...you are
facing the inner (disc) side...and oriented so the round
protuberance of the outer casting is TO YOUR RIGHT, and the
LEVER is UPwards to its stop...about 1:00; THEN, the elliptical hole of the disc is roughly
opposite the upper left casting screw hole, say
11:00....and the 4 tiny disc holes are roughly to the lower
For the RIGHT
carburetor enrichener unit, as in these various photos, for the SAME orientation of
casting and lever...the disc is REVERSED...that is...the 4
holes are to the UPPER LEFT, and the elliptical hole is to
the lower right.
Here are some photos that will
further explain things. These are from RIGHT SIDE carburetors.
The above photo, marked
has the dimple in the wrong
This MAY be
necessary if your DISC/shaft
was wrongly assembled or
stamped by the
PLEASE RE-READ THESE
TWO SENTENCES AGAIN!!
Yes, you could press it all apart and fix
the direction...but I suggest you do NOT!
Just below is a photo of a CORRECT
LEFT side enrichener. This is from a
rather late model, and you can see a
tiny bit of the brass disc, through the
left end of the elliptical hole. Note
that the upper-most of the tiny holes
is counterbored, but NOT DRILLED,
thus, it is not operating as a jet.
This varies with model.
Later model Bing
CV carburetors have two-piece cable levers.
It is possible to WRONGLY install the two metal pieces. It is annoyingly
EASY to overlook this, and you won't notice until you have
the carburetor fastened to the engine. Lever parts can be installed upside down AND/OR reversed in
position. In BOTH Left and Right carburetors,
the part that has NO notch (no slot)
for the installation of the cable wire, goes onto the carburetor enrichener or throttle shaft first, and note the enrichener here with its offset facing the
carburetor body. The outer part, that DOES
have that notch (slot),
can be installed wrongly, flipped-over if you will.
Install it such that the notch does NOT
face upwards during cable operation. Here are photos of how the later
model levers and springs look when
installed properly. Note how the short tang end of the enrichener spring fastens to the top, and further notice how that spring is on top of the enrichener lever, not the underside. To see why I install them this way, actuate the choke and note that the spring is not interfered-with by the lever, etc., as it moves.
This photo of the controls side is from a RIGHT side late model
This below photo of the controls side is from a LEFT side late model:
NOTE that for a
smooth AND PROPER enrichener operation, the enrichener needs to be
faintly lubricated, cables good, and operating lever cable
lubricated (IMPORTANT or cable can break strands!)... and if you have them, the T barrels under the
fuel-tank where the one cable from bars splits into two, in good
condition. There is an O-ring internally on
later enrichener models. I lightly silicone-grease that O-ring.
the fuel bowl gasket MUST BE IN GOOD CONDITION for the PROPER operation of the enrichener. The reason for this is complex, but a simple explanation concerns the tiny diameter pipe that comes down from the enrichener circuit in the carburetor top body, and dips into the enrichener fuel well in the bowl. That tiny pipe MAY have one or two holes in it ABOVE the pipe lower open-end. There is also one or two holes were the pipe joints the carburetor body, not discussed here. Vacuum, during the starting sequence with enrichener ON (CHOKE as marked on the bars assembly) causes fuel to rise in the enrichener well in the bowl to a higher level than in the rest of the bowl, creating even more richness than might otherwise be possible. The operation of the holes, if any, in the tiny tube is complicated, so won't get into it. BUT: If the gasket is leaking air, the maximum enrichment could be LESS.
NOTE: due to the over-all enrichener design, the amount of enrichener to be used, and whether or not you need a bit of throttle opening during cranking/starting, and after just starting, can be rather variable.
Most owners booklets say to not open the throttle, as it defeats the enrichener, and this is really a vast and not necessarily true simplification. You very well MAY need some throttle opening immediately after the starter motor starts cranking the engine, and during starting, and this depends a lot on the particular motorcycle tuning and temperature, fuel volatility, etc. In cool or cold
weather, full choke may be
needed for starting AND,
very contrary to all the 'books' nice verbiage, you MAY
NEED to manipulate the throttle during cranking.
In one early version of Clymer's manual that I saw, in the early
section on how to start your motorcycle, Clymer's has the
operation of the choke lever (on the early models where
said lever is on the clamshell of the air cleaner housing),
BACKWARDS. The truth is that the
lever must be HORIZONTAL for the choke to be OFF....and
DOWN for choke ON (starting). Clymers fixed this in later versions of this manual, although I did not check all sections of the manual. Maybe I had something to do with fixing that first mention?!?
Very early Bing CV carburetors have pressed-in float bowl enrichener
jets, not screwed-in.
The enrichener (choke) is held to the
carburetor body by 4 screws. These
screws are infamous for loosening, and the gasket can then get sucked-in a bit, and the carburetor not work correctly, even with the choke lever off. If the
carburetor is still on the motorcycle, I recommend, that
once the throttle and choke cables are removed from the top
of the carburetors, that you loosen the carburetor adaptor
clamps and rotate the carburetor to allow the tightness of
these 4 enrichener screws to be checked. If loose,
either tighten; or, remove and use a wee drop of Loctite blue on the theads
and then reinstall and tighten them. They CAN be tightened without
rotating the carburetor, but it is typically a big hassle, even
with several types of offset screwdrivers. If you wish, you may use the faintest possible smear of some sort of
NON-silicone gasket sealer on both sides of the gasket. REALLY faint! Gasgacinch; Permatex Form-a-gasket (non-hardening), etc.
NO RTV HERE. The reason is not to
prevent leaks directly, but to help prevent the gasket from
sucking-inwards, which then DOES cause leaks. I do not use any such sealants, but I do, during overhaul, make sure the cover and body it fits to are FLAT, with NO proud metal. I surface the cover, disassembled of course, on 220 grit paper; and, use a very fine file, very carefully, on the body mating area.
***Do not remove the throttle butterfly valves unless the
shafts are really worn or leaking, as they are O-ring
sealed, the screws peened, and the shafts can still be
leakproof with a fair amount of side play due to the
presence of the
O-ring. To test for leaking, spray the shaft area from the
outside of the carburetor, where the throttle lever
attaches, with brake cleaner, while engine is
idling. The idle speed must not change.
If you do change the shaft O-ring, DO coat it, a bit
more heavily than faintly, with silicone grease. They
will then last almost forever, and operate
smoothly. If you DIP the carburetor into a
cleaning tank for any period of time with the usual harsh
carburetor chemicals as used by professionals, you will HAVE
TO replace the shaft O-rings. If the shaft is removed, then you must decide on the
screws, to replace or not, to peen or Loctite them.
butterfly can be put in backwards. Do
NOT!!!! That is why I previously said to mark
the butterfly!..top, rear...or similar. This is a
CRITICAL point. HOWEVER, I highly recommend you check yours, as maybe they are already installed wrongly!
The fitment of
the lower edge (and the sharp shape at that point) of the
butterfly is critical where it comes close
to the the idle passageways holes at the carburetor
bottom. Putting the butterfly in backwards will
eliminate any chance of proper off-idle throttle
performance. This is doubly
important with a dual plugged machine in which the
butterfly is more closed at idle. If you
install a butterfly wrong, you will NEVER have a good
stable idle. When installing the butterflies... as you slowly tighten the two
screws, you must lightly
press the butterfly with a finger, into the main carburetor bore,
to align the butterfly...it is important that it fits the
bore very evenly, and for minimal clearance (shine a light
through the carburetor as you look from the other side). You may have to unscrew the IDLE STOP screw at the throttle lever some, to close the butterfly valve enough for a proper look-see.
If the butterflies are reversed, you will never get proper operation.
The later enrichener (choke) control and all throttle
controls on all the carburetors, each have an outside return spring.
The springs are not the same. The old style
carburetors had the enrichener (choke) lever on the aircleaner
housing, and springs were not needed as the cable inners
were very stiff single strand of steel wire. The
lever assembly at the air cleaner snail housing can be disassembled
and cleaned and lubed, as they tend to get stiff with
age. It may be necessary to adjust a size of a thin shim to allow smooth
action...as you do not want the nut loose. Sometimes
that area takes some fiddling with.
styles of throttle return springs were
used. The earliest type fit AROUND the throttle cable
center. It was not a good type, and the throttle was
pretty stiff. Later types had the springs
attached to the throttle lever and a carburetor boss projection with a
tiny hole. If a spring is stretched or
misshapen, replace it. The spring must not rub
against the carburetor or parts, if it does, change the inner
fit to outer, where the cable barrel
joins the lever. Far nicer throttle feel
can be had by modifying the oldest style CV carburetors so
that the spring is NOT wrapped around the throttle cable
outer sheath. Not a simple thing.
Hate to repeat myself, but....If
you remove any jets, etc., that have O-rings, you SHOULD
replace those O-rings. I prefer to put a faint
smear of silicon (or even petroleum) grease on
the O-rings when assembling to help avoid cutting them
(the tape over threads helps as does room temperature or
a bit above, as opposed to freezing weather). Also
I put a truly faint amount of silicone grease on the threads
The one jet ASSEMBLY that I always recommend be removed, to
clean that area in the carburetor is, in order from the
bottom (for your future reference): the central main
jet; the washer above that (do not substitute the type of
washer, don't leave it out); the so-called mixing tube
(brass part, with O-ring and outside threads, with 10mm hex
sides) above that; the needle jet above that; and the
atomizer above that. This information is for those who have
removed things, have not 'seen' the direction of assembly,
or have forgotten the direction of the parts. Note previous cautions about
screwing in the central jet, not to trap and crush the
needle, and note also that the
atomizer (the top most part) fits only one way, and it will
then, properly, stick upwards INTO the throat.
The needle jet, which looks like a
machined brass tube of two basic diameters, and is often
marked with a number, such as 2.64, 2.66 or 2.68, fits with
the small tube portion upwards and its slightly curved
[internally] end downwards. Above that part is the
atomizer, which is a machined brass part of three differing
diameters, the slightly
smaller diameter goes upwards and fits through AND
INTO, the carburetor venturi (throat), and its
lower portion has the holes. On RARE
occasions this part might not seem to fit and does not seem
to want to poke up through the carburetor into the venturi.
If the smaller diameter end is up, the side-holed end down,
this is correct, and you may have the part slightly tilted,
or, tilted and under a tad of too
much pressure from the 10mm wrench area below. You
can install that atomizer by itself, and hold it IN the
throat, perhaps using a toothpick to get it properly into
position and then fingers to hold it in the throat, as
you assemble the lower parts.
You MUST assemble the
central jet assembly parts in the correct order. Do
not over-tighten. If the slide/needle is
already installed in the top of the carburetor, be
cautious about not letting the needle hang up on the
central jet parts!
The central jet assembly O-ring, with
the faint smear of grease, will reduce friction, and you
should be relatively gentle on the force you use on the
10mm wrench, just barely tight. Antiseize or silicone
grease on the brass threads make for less
corrosion and seizing possibilities. Remember that
the carburetor body is made of a soft and not overly strong
material....zinc probably. The danger is in cracking that
central carburetor boss. I grease the threads
VERY lightly, silicone or anti-seize. Those
that over-tighten the central jet assembly, and fail to use
a lubricant or anti-seize, are asking for seizure, years
Cleaning the idle system...jet, holes, etc...is important,
and the Berryman's works well, if allowed to work awhile.
DON'T bugger the end of
the idle jet with a poorly fitting screwdriver.
Rarely the idle jet has been known to freeze
in its threads. If you break off half of the
screwdriver slot end, drill it carefully and use something
like an EZ-out. I will use heat on the
surrounding alloy, to try to enable removing, before going
When replacing rubber O-rings which you must push over threads, you might have the thought that the threads might cut the O-ring...yes, they could. The slightest cut will eventually expand to a wide cut or break, and leak. A simple way of avoiding that possibility is to not only grease the parts with a very THIN layer of silicon grease....but to FIRST wrap a single layer of any sort of tape around the threaded part, and THEN slide the O-ring over it! I use my smooth thumbnails to push the O-ring into position, sometimes using a teeny SMOOTH, totally NOT SHARP, dental hook, especially for the last bit of movement into the groove for it.
Don't fail to spray clean the jet in the 'well' of the
bowl, and the overflow tube too. I've sometimes had to poke
around at that jet with a piece of wire to clean it.
The left and right carburetor bowls are NOT the
same. The corner well, containing the jet at
the bottom fits the tiny diameter tube projecting downward
from the carburetor body. This is the
enrichener fuel source.
I always clean the various metal
parts with the mentioned Berryman's brand of
carburetor/choke cleaner spray. For a major overhaul,
take everything apart and use a professional cleaning
tank, especially a heated one, if you have one
available. There are many types of spray
cleaners available at your local auto parts store. Some are
NOT very good. A good one will instantly dissolve a fair
portion of the brown stain deposits if you have some, on
the carburetor outsides, sometimes a cotton
swab will help. I prefer the spray by Berryman, called B-12
Chemtool, Carburetor & Choke Cleaner. This is
nasty stuff. Hopefully Government regulations will
allow it to continue to have the strong formula. Use outdoors, or with your garage door
open! It is also very good in just spraying off the
stains on the carburetor outsides now and then.
Common so-called 'brake cleaners' are AWFULLY BAD at
cleaning carburetors properly. I use Q-tips, tiny bits of cloth on forceps, toothbrushes, other solvents, etc., to really REALLY get everything spotlessly clean, inside and outside.
Be sure the main jets and needle jets have the proper and
same size number on them, left and right. If you have
removed the idle pilot jet, be sure the numbers
Every once in awhile, someone asks about removing, or
changing the setting of the slide needles. Even when
there is a definite reason, such as gross modifications to
the exhaust system, or the carbs are U.S. specification and
you want to richen to the British specifications; changing the needle position by one
notch is often WAY too much, and the better method is to
change the needle jet to the next size. In
many instances the British-shipped carburetors have both
needle size and needle jet size BOTH changed. Another approach
is to ASK BING!...they are usually quite helpful...and
their carburetor parts and service booklet is worth the $.
When installing or removing a slide needle, the early common type
of needle is the twist/push-pull/turn type. For them, the
proper method is to clean them and your fingers, so they
both are clean and dry, and grip the needle tightly with
thumb and forefinger, and rotate left or right, pulling
slightly downwards or pushing upwards. EACH 90 degree rotation will allow
ONE needle notch of change (if also pushing or pulling).
UNDER NO CIRCUMSTANCES BEND THE
NEEDLE. Rotate one direction, then the
other, as required. Some may find that a thin piece of
leather will help. NEVER use
pliers!!! ONE (1) 90
degree rotation per so-called needle position!
Be sure both carburetors have the
needle sticking out of the slide the same amount. Use
a caliper, and measure closely. ***I
HIGHLY recommend that you check the
slides/needles for distance, to be sure they are the same,
as well as to write down the distance, BEFORE
removing or installing or changing the needle position. You
cannot 'see' the needle position on the early style, it is done by feel, and
having a measurement (you need to be accurate to maybe +-
.015") may save you some considerable hassles. I
measure them with a common vernier caliper. You can
measure the underside of slide-to-tip distance, or, the
distance from top of slide assembly 'tube' to needle tip.
Needle position (there are typically 4 positions available)
is measured from the top slot position of the needle. Most
needles are in the #2 or #3 position from the top.
The other, later type of needle is not held in by the hidden clip in the same manner. There is a screw in the top of the slide. Remove the central screw from inside the slide, and turn the slide over. The needle should fall out the top into your hand, with a little clip on it around one of four positioning slots. Later needles may be aluminum, and if the clip grooves are worn enough so the needle can move up and down with reference to the clip, easily, replace that needle! NOTE!....The
SLIDE needles should be replaced at the 60,000 mile
intervals I recommend, or tad sooner, and always with
the associated needle jet.
is a particular problem with the aluminum or similar needle material on some
1985+ models, in 32 mm size. There may be some
other carburetors with this problem. The NEEDLE
grooves WEAR, due to the type of metal
used. If the groove wears enough, the needle
will not deliver the properly metered fuel.
Watch for this, it is little known. Replace the
needle and the clip! You can get weird
symptoms, even backfiring, if things wear enough.
Check BOTH carbs!...they do not, for whatever
reason, wear at the same rate.
The carburetors should be mounted
squarely to the motorcycle. View from the top, and a few
feet to the rear of the bike. Do NOT tilt the tops
towards, or away, from the motorcycle.
The rubber 'hose' adaptors from the carburetor to the
cylinder heads are sometimes found to be leaking.
This is usually proven by spraying them with any spray
cleaner such as 'brake cleaner' at idle speed...should be
no idle speed change. Keep the screws on the band-clamps
tight. This is the perfect time to spray the
throttle shafts too. NO
idle speed change at all is proper and the only thing acceptable.
CARB TOP STAINS:
Fairly often I see carburetor top stains where they join
the body of the carburetor. The tell-tale sign is a brown
(usually) stain around the diaphragm joint interface,
caused by some tiny gasoline weepage. I was never
bothered by this, as the 'problem' is sporadic and
minuscule. However, Oak
sent me (in 1984!!) a bulletin he made up describing this
situation as not necessarily being caused by the lack of
the diaphragm acting as a seal, but rather that the
compression of that diaphragm was insufficient for a
COMPLETE sealing. He recommended removing the carburetor
and flat sanding the carburetor top itself, with 220 grit wet type paper,
kept wet with water,
figure eights, carefully, until the groove, which he said
was 0.155 to 0.156 inch deep in the troublesome carbs, is
reduced by about .007 inch. He said to shoot for a final
depth of about 0.147 to 0.150. Remove all grit. I have done
this to several carburetors, and it DOES stop the staining.
Frankly, few of you have the gauges to measure this, so you
could try just a few
figure eights. TEN is appropriate, LIGHT medium pressure. Do them EVENLY. Once the fresh sanded surfaces
are evenly fresh all the way around, that is likely
enough. Do not overdo this. Clean and reassemble.
LEAKY TOP PLUGS:
Some carburetors (not the flat top ones) have had leaky
steel plugs on the domes...that shiny center area. You can
easily test the plugs for leaks when the domes are off for
servicing the carburetors. DO NOT
allow any leaks...it will act like a torn diaphragm. They
can be crimped or epoxied. I prefer crimping with a tiny
tip punch and then epoxying. Some folks have used a
toothpick and aluminum paint. If your plug has
a letter C stamped into it, do not cover it up, it means
something....it identifies an early modification in the /5
era. There is a BMW Roundel that can be
epoxied to the top of the carburetors (they fit the small top ones, also the flat top ones, which can also use much larger ones too).
article on this website, for a huge list of Roundels,
including exactly which fit nicely the small tops.
When cleaning the area for epoxy or aluminum paint, etc.,
it is very difficult to get sandpaper into the corner.
I use a dental pick or awl.
HARD STARTING, maybe ONE carb
does not work well initially, then works OK after engine running
& throttle opened:
If starting is still poor, it may be that the slides are not returning
fully. Older advice was to check for that and fix by installing springs 13-11-1-335-324 above the slides
on 40 mm carbs, and 13-11-1-338-134 on 32 mm carbs. This did not apply to the flat top carbs.
Tom Cutter once said that this modification, installing a longer and softer
spring on the slide, will smooth the idle transition at the 1/8th
to 1/2 throttle movement. Tom said that the shorter,
earlier spring, used on the 40 mm Bing CV carbs, was 13-11-1-335-324. He installs spring 13-11-1-338-134, as used on the 1988-1995 R100 models
using the 32 mm carbs (these springs, per Tom, are used on the
EURO R100GS 40 mm carbs).
I have my own input on this. Some
folks DO prefer the more abrupt throttle action of the stiffer spring, which is
about 115 mm long and has about 30 coils. The softer springs are about 120
mm long and have about 20 coils.
If you have done most everything, and
you have problems starting the bike, consistently hard
starting, or maybe ONE carburetor is acting up, that
cylinder not firing (maybe even until engine warms a bit)
and throttle is opened.....check that the enrichener was
properly installed, no matter if the dot-dimple on the shaft looks
correct.....and if still a problem.... see if the butterflies were properly
installed. Not only is this to include loosening the screw whose bracket
keeps the shaft in place, but loosening the butterfly screws (a problem if peened, if not, when tightening, use Loctite BLUE), and be sure the butterfly
will completely seal to the carb bottom (idle rpm screw loosened A/R).....and tighten things
again. If the butterflies are reversed, you will never get proper
If you have a R75/5 that is particularly a bear to start (or,
one carb is not working at startup), and everything else checks out fine, be
SURE to check the slides, to be SURE they are BOTTOMING fully, and not
hung up slightly. Install the springs above the slides.
This problem is rare, but has been seen on them, and VERY rarely on
later carbs. Polishing the slides and inside carb body can help. There is a very complete article on this website about R75/5 carburetor problems: http://bmwmotorcycletech.info/earlybingR75CV.htm
there are complaints of hard-starting bikes. The owners
have checked everything, including valve adjustments, compression
pressure, spark plug wires and caps, coils, everything....and the
bike still does not start OK. Check the slides on CV
carburetors, be sure they are fully bottoming.....there is a
spring on top of the slides on some models, to help with this.
ON all models, and the Independent float KITS too;....the
floats are adjusted by bending the tab
that the float needle (and wire clip, if used) attach to. I
have found a TINY screwdriver does this OK, and seems to
work better than unwieldy long nose pliers. Do one
carburetor at a time. BE GENTLE
AND CAREFUL!!...do it evenly too...not at one
edge, which bends the tang on an angle you don't want.
In other words, keep the tang flat and square. It is spring-y, so eyeball your work.
After making a small change...
turn gas on, lift float gently and SLOWLY with
protectively gloved finger, until the gas flow JUST
stops. At THAT point where the gasoline JUST
stops flowing, the top of the stock floats are to be
parallel to the lower body of the carburetor. I allow as
much as +- .020 inch. I have done some
fine-tuning by playing with the float level, I suggest you
do NOT. Some
folks find it easier to lift the float until the gas stops
flowing, and then very very gently lower it until the gas
JUST flows. This MAY well be
the preferred method, as it eliminates the effect of the
spring loaded lower tip on the later type float needles and eliminates
any play in the pin and hinge holding the floats in the
For the KITS, the adjustment is the same, but the measured
distance is .412" from either lower arm edge to the
I have information on this website
....originals of some Bing documents, some of marked-up copies, crude, but useable...all of various Bings sheets on
installation and adjustments of the independent floats KITS. Here is a
Be gentle and careful about doing any
bending. Float level affects richness-leanness and gas
Major tuning/adjusting the carburetors is not part of this
NOTE and HINT: On earliest models the band clamp at the carburetor throat inlet should have its adjustment at the TOP...or, at least not at the bottom. The models most affected are those with the plastic tube having slots in the band-clamp area. If the
band adjustment is not above the bottom, the breather
output oil may drip on your foot, depending on if there is
a slit or not on the tube; this was particularly so on the
Additional information on Bing CV
carburetors will be found at http://bmwmotorcycletech.info/bingcv-2.htm
to 12-07-2002: mostly
Through 12-09-2002: add area for upcoming float
testing; added references to Bing CV Carburetors-2,
clarifications and emphasis items. This
version was not to be released to
the website, pending more
01-30-2003: Updated many places, decided to release
to the website even though float testing has not
begun yet. Added a complete section on
the enrichener orientations.
03-30-2003: extensive information on Bing dual
independent floats added.
06-21-2003: Add NOTE and HINT on band clamps.
07-13-2003: Add all information on float testing
done; clarify many areas.
07-14-2003: Edit for clarity
07-20-2003: Add note on float/float pin clips not
being used on some models
07-22-2003: Expand about the two types of retaining
for the slide needles
09-30-2003: add top of article notes on Gary L.
09-30-2004: add url for Bing's chart of component
description and numbers
02-15-2005: minor updates.
02-18-2005: hyperlink to bingindependent.htm
11/30/2005: update enrichener/choke information
04/23/2006: add emphasis note on screwdrivers for the
Bing tops. 04/24, modify that again
05/11/2006: Bing diaphragm caution note
08/24/2006: Add photos of enrichener
parts/orientation (left parts)
03/04/2007: more information on the Stromberg
diaphragms and cautions on their use.
05/03/2007: Fix hyperlink to BMWMOA.org; and
generally update the entire article
07/06/2008: replace enrichener photos with better ones.
04/19/2010: Expand description of the enrichener
parts assembly and alignment, regarding the dimple,
later in evening, add more comments, so is no mistake
about how the
enricheners all assemble.
04/25/2010: Add photos, Posi-Drive screws and
today go through the entire
article, simplifying, changing to more legible & less
fonts & colors. Especially, fix the Enrichener
section, making clarifications,
adding photos, etc.
Final version release 3:12 PM PCST
02/16/2011: Added another view of enrichener cap
Clarify the enrichener a tad more, and remove one photo
that was confusing.
08/15/2011: Revise diaphragm and Stromberg
05/14/2012: add butterfly photos
05/17/2012: Clarify information on the slide springs.
10/14/2012: QR code and google update code
11/06/2012: Expand Bing independent
10/09/2013: Add more to information on float needle and seat.
07/15/2015: Update a few areas for increased understanding/clarity.
09/03/2015: Add photo of carburetor with control lever springs and orientation. Clarify some details in various text areas.
09/05/2015: Add more photos and text, and clean up some. Finish-up, and reduce colors, etc., on 09/07/2015
09/12/2015: Remove the long section on float testing, and move it to a new article. Reduce colors/fonts, clean-up.
copyright, 2014, R. Fleischer