Bing
CV Carburetors, overhaul, etc.
©
bingcv.htm
3
(SOME, not all, overhaul notes)
see also, bingcv-2.htm
>>A
basic mini-overhaul can be done with the carburetors in
place on the engine. Quite frankly, this is often
quite enough.<<
*************************************************************************************
For a well-done 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
at: http://www.bmwmoa.org
from that page, click on left side for Country
Store, and then on the Country Store page, go to Back
Issues.
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 too!), be SURE to MARK
the butterfly for correct refitting: something like
TOP, OUTER; or TOP, facing REAR...or something of that
sort.
4. The article you are reading will have 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
parts numbers!
http://www.bingpower.com/english/service/einstellblaetter.html
**************************************************************************************
OK...on to the MEAT of
the article you are reading:
The float needle tips
tend to get faint grooves in them after a lot of miles, and
the tip material gets slightly harder, and then the needle
tip does not seal well, causing the bowl to overflow onto
your foot. This can also happen if a TEENY 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.
The stock dual 'one-piece' plastic float assembly does not
always fail by getting considerably heavier; yet when bad,
it will sink in
gasoline (essentially hardly any will be above the surface
in a container of gasoline in which the float, without pin
or anything else, is trying to float). Once it deteriorates
and sinks with little or none showing above the surface,
your mileage will get worse and worse, eventually perhaps
flowing onto your foot.
If you question this strange situation, I suggest you
weigh some good and bad floats. I have measured good floats
and bad floats, and they seem to show a weight of about 192
or 194 grains when new; and, as they age, either seem to
reduce to about 186, and then a bit less, or they increase
a fair amount. Seems they are not consistent in how
they fail, and that MAY be due to the type of gasoline they
are used with. New floats weigh about 13
grams. A horrendous badly sinking old float that
almost sunk totally was 18 grams. MOST stock
white one-piece floats will get heavier as they
deteriorate. Once they are removed from
gasoline and very thoroughly dried, which can take a lot of
time, they may lighten considerably, and then not gain much
weight if again put back into gasoline....at least for a
month or two period of time.
The conversion factors are:
1 ounce = 437.5 grains = 28.35 grams.
15.43 grains = 1 gram
The reason for the floats failing when they weigh less is not well understood. It SEEMS to be a shift in mass, and the outside dimensions do NOT hardly change. Remember that this does not always happen, and the floats mostly fail by increasing their weight. The floating test is the only good test.
Information from extensive testing on a large number of floats was FINALLY! completed, after some months, on July 13th, 2003. I had accumulated a goodly quantity of used Bing plastic 'one-piece-assembly' floats, for which I hereby give special thanks to all those who sent them to me. These floats came from both slide and CV Bing carburetors, some were very old indeed, and others not very old at all. Testing took months. Since the floats were WELL dried out when I received them (I hardly understood a problem THAT brought about, at least at first), I had to take measurements of various sorts and then put them in sealed glass containers with various fluids, and let them soak at least a month, and then retake many measurements. Weight was a primary concern, but I was also interested in mass, distribution of the weight/mass, dimensional changes, etc.
There were some surprises. I had
EXPECTED to find that some solvents would actually start
visibly destroying the floats, but this did NOT happen. All
sorts of solvents (well, liquids) were worked with, many of
which were known ingredients in gasoline's from across the
country. I obtained samples of gasoline free of alcohols,
free of MTBE, free of ETBE....etc....as well as gasoline's
WITH those additives. I did testing of the floats in
specific liquids/chemicals. I also did some testing by
MIXING various chemicals/solvents, as just putting floats
into a single solvent is not, theoretically, adequate to
establish all possibilities.
I hardly think I exhausted all the
possibilities.
A bit of background follows, then the float testing
results.
Alcohol, ETC: Some additives are used as 'co-solvents',
that is, adding them ALLOWS other additives to MIX with the
gasoline, that might not mix by themselves.
Yes, this allows WATER to mix with the gasoline, among
other things. Some additives are used mainly
for oxygenation purposes. Theoretically, under
some conditions, adding something that contains more USABLE
oxygen, per unit of volume (or weight) will allow a fuller
burning of the fuel. Under SOME government
mandated test routines, they lower the 'smog' output of the
engine, BUT, they USUALLY cause a DROP in mileage, causing
more smog....in SOME ways anyway, as in LESS mileage...and
SOME types of emissions ARE actually increased per mile
traveled...they are just not the one's the government
agencies have a priority on at the present time. Use of
alcohol (and several other additives) containing fuels will
almost always result in a LEANER burning condition,
generally meaning higher engine temperatures, and if
severe, can lead to burning up pistons, problems with the
valves, and even an engine seizure.
Whilst alcohol has a higher octane equivalency, it requires
a LOT more VOLUME of alcohol. In order to
maintain more consistent burning, one really should change
one's jetting (needle and main jet) to a slightly RICHER
type, if alcohol fuels were used all the time, and the
fuels were consistent in makeup. riiiight!!
This would REDUCE gas mileage even more than such fuels do
with the stock jettings, although driveability would be a
bit enhanced.
Use of alcohol fuels is, in my mind, absolutely forbidden
in PREMIX type of 2-stroke engines, as the alcohol and
water can separate out of the oil, and the engine seize
from lack of lubrication. In the airheads, it is not a big
problem, but alcohol CAN cause 'driveability
problems'....poor throttle response, hiccuping, jerking,
lousy warmup. If your bike is already lean running, and
airheads from the 1980's, especially those exported to the
U.S. are like that, you might have WORSE driveability
problems....or...overheating. Testing for alcohol can be
done rather simply, but it is a PIA to do at every fillup,
and this type of testing (mixing in a test tube, with
water, see if water level rises) also will show up MTBE,
and some other additives that absorb water. California's
reformulated gasolines are a problem, and this has spread
to other States, although California will eventually phase
out MTBE in every part of the State.
Some States require labeling the pumps, some do not, some
only if the % of alcohol or ??...is at some particular
level or beyond.
There are THREE common types of
alcohol, isopropyl (rubbing alcohol), ethanol (drinking or
corn) and methanol (sometimes called wood alcohol since
that was one way of making it, nowadays it is made from
natural gas; and, it is very poisonous and quite
corrosive). Generally speaking, methanol can cause
corrosion of aluminum, can be hard on rubber and plastic
parts...and brass parts. THAT covers just about everything
in your airhead's carburetors but the steel pin and needle,
and the diaphragm, and those can be affected with water in
the mix. Other additives are not great either: ketones,
ethers, etc. Common 'gasohol' has 10% alcohol, but may
contain LOTS of other 'things'. The alcohol in gasohol will
raise the octane, but leans the gas mixture, which is why
most FI cars can get away with using it (at a cost in
mileage and some in power), but many older carbureted
vehicles will not like it.
Because of the horrible additives used in gasoline's today,
gasoline can NOT be stored as long as it used to be, not
even with an additive you purchase such as StaBil. The
gasoline will deteriorate, not good for tanks, petcocks,
hoses, and, of course, the carburetors. It tends to gum up
during that deterioration. The better of the alcohols
is isopropyl, it tends not to separate out, and is fairly
stable. Isopropyl, however, is not the alcohol of choice of
the vested interests that grow or sell corn or the
politicians who have, well, interests in this area.
It is hard to give solid recommendations on storage of
today's gasoline's. Generally, with the use of
a product like Stabil, a few months is the best one can
hope for. It is better to clean and then dry out the
system. I do, however, have mixed feelings, even
about doing that....as opposed to cleaning and drying out
the TANK only.
A product often called 'dry gas' is sold to car owners in
wintry States, as it, an alcohol...usually methanol or
isopropyl, mixes with water at the bottom of the tank, and
in fuel lines, enabling the water to be 'burned' ...so to
speak. Adding that product MIGHT increase the alcohol and
water content of the gasoline to a critical level...that
which would cause a separation process...and water and
alcohol will now be at the bottom of the tank, rotting out
the tank....or, worse with a premix two-stroke
engine....the oil could separate out, and the engine would
not get lubricated.
Types of liquids tested:
methanol
isopropyl alcohol, high % as well as mixed with water.
ethanol....medium %, as well as 154 and 191 proof..
above with varying water content as well as chemically dry
(anhydrous).
toluol (toluene).
California MTBE gasoline.
Known standardized Chevron 91 octane fuel.
California reformulated alcohol added Gasohol.
leaded fuel.
motor oils.
a solvent consisting of a light aliphatic complex with
naptha's, toluene, xylene, methanol, acetone and MEK.
common denatured alcohol.
Xylene.
MTBE high concentration.
a solvent consisting of toluene, n-butyl acetate,
2-butoxyethyl acetate, and a few other things.
ETC.
RESULTS OF ALL MY ABOVE TESTING:
I. Weight change (weight is in 'grains'; there are 15.43
grains per gram):
Used floats tended to be in
the range of 185-255 grains when well
dried out. After soaking for weeks in various
chemicals/solvents/gasolines, one particularly bad set of
floats was almost 262 grains immediately after removal from
MTBE containing gasoline (allowing a couple of minutes to
evaporate the surface liquid). This was a very bad set
indeed. But this set was 255 as I received it. This
means that whatever change happened to these floats, it was
mostly permanent. Typically the weight change
occurred during the use on the motorcycle, with only some
more moderate increase when put in the various liquids.
This suggests that the aging is very slow. MTBE
is only ONE of many harmful substances.
***I should note here that some folks
sent me information on weights that I could not duplicate.
I was rather suspicious, and then I made an interesting
discovery. If a float was never dried out thoroughly from
first being put into service, UNTIL removed and replaced, and
then sent to me, then the weights might tend more to agree
with information I was given, as those weights were taken
right after removal. My conclusion was that it
is likely that the first (since brand new) and constant
immersion in fuel changes the float in weight/mass movement
vastly more on a percentage
basis, than after the float is dried out from some years of
being in service, and re-placed into gasoline.
This might show up as a smaller effect if my testing had
gone on for MANY months in the various liquids.
MIGHT. I was a bit intrigued by this
idea. I did some experimenting with cutting open and
drying, a few float assemblies, but NOT loosing any of the
material...and it appears that my hypothesis may well be
correct. While someone could compensate their floats
for this effect (by measuring actual depth in the float
bowl and adjusting for that....AFTER drying the floats
really well after long usage....it is a moot point, as I do
not really recommend this. Saying this
all a bit differently: it APPEARS that a brand new
float, once put into gasoline and kept in gasoline (except
perhaps for very short periods allowable without
gasoline...such as carb bowls off, perhaps for a day's
overhaul), changes internally, and that internal change is
permanent...or if not, it takes a VERY long time for the
change to revert any.
II. Some special tests were made to determine if there was
a shift in the concentration of mass. This WAS found to be
so. This was not excessive, but combined with an over-all
change in weight, was more prominent than might be
expected. A small change in mass movement, plus a
small change in weight, would be enough to cause a float to
sink a fair amount.
III. Change in dimensions: of each float assembly, both
sides were measured for width and length. There was a small
variation noted even with brand new floats. One surprise
was that the dimensions changed very little from
new. I theorize that the outside of the float
tends to harden some, and become slowly more impervious,
whilst the nastier fuel components get inside and do their
damaging work on the float inner portion.
IV. Other changes: INternal discoloration was NOT noted on
some, but the worst were ALWAYS discolored.
Almost no truly bad reported (by sinking noted by owner)
floats were still white on the outside (although some were
INternally a bit darker).
ONE SPECIAL THING WAS NOTED!! As the floats became
worse....that is, they tended to sink in gasoline more and
more...and usually became heavier.....the INside of the
floats tended to turn into a somewhat MUSHY and almost
granular mixture, even if left out to dry for a
considerable period of time. ONCE cut open, they
would dry out, although this took a fair amount of time...several
hours, and not fully for a few days. The OUTside
tended to be a harder 'shell'. The conclusion is that
whatever the exposure medium was, it tended to migrate
INside and make changes to the contents, and generally
INcreased the internal mass weight. Mushiness
and granularity was not the only change noted!...there was
a small shift...mass movement to change the CG! The worst
floats tended to have small voids in the floats (bubbles or
similar). My suspicions are that something...perhaps
something in gasoline I did not test for....may be
modifying the insides of those floats, besides the fuels
tested. It is also possible that the initial brand new
float change to the interior is actually the effect of the
things I tested for, but would take many many months.
There was absolutely no doubt that MTBE containing gasoline
made the interior of the floats mushy.....but surprisingly,
since Bing touts its dual-independent floats as
'alcohol-proof', I did not find big changes with alcohols
of any common type! My suspicions are that some dyes
may be at work here too. Again, other things besides
MTBE are suspected by me of causing the interior changes.
Follow-up: I managed to obtain a float and do some retesting during the late Summer and Autumn, of 2005. This time, I measured only weight, and the only liquids being tested with the floats, after a couple weeks of soaking, were hi proof ethanol; anhydrous methanol; and a refinery product of mixed solvents/items, that I obtained from a refinery worker....this type of mixed solvent is a byproduct, generally, and is often mixed into batches of motor fuels, to get rid of it...and for?? reasons. Also, in this particular series of tests, only the SAME float assembly was used, thereby exposing it to a series of solvents. The float assembly started out as 197.2 grains, and no matter what solvent, nor at what period of time, the weight never exceeded 210 grains. I was able to obtain some other exotic solvents, and did some brief testing on them. Same results, tad worse.
Bottom line: I am almost certain that the problem with the one-piece float assembly is one of very very long term exposure to a mixture of various solvents in common gasoline's, and that those gasoline's that have, perhaps, alcohol and/or MTBE, or similar, will be affected MORE.
<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>
The Bing Independent Float 'kit':::
I do NOT recommend Bing so-called
alcohol-proof float kits (dual independent
floats). HOWEVER...if you are willing to fiddle with
these, and understand the limitations, then their use is OK
with me. There are several reasons. Bing said,
years ago, that they would give increased mileage and
performance due to stability of the fuel level during
turns. Perhaps in an airplane or with serious
racetrack use. They were originally advertised as
being for engines where the carburetors were facing more
left and right than our airheads...more or less fore and
aft. One must think about the way the floats
are hinged and operate, and then one will see that Bing's
old claims for our bikes were hardly reality.
As to their NOT being affected by 'alcohol'....that may be
true, but, even though I have NOT seen any of these
independent floats fail, the stock floats are fine, but you
do have to replace them every 30K or so. For EITHER
the stock OR Independent kits, you MUST replace the float
NEEDLE regularly....as it is the SAME needle, for BOTH.
The Kit float level is somewhat difficult to
initially adjust, having TWO flimsy brass arms. The
arms contact the floats via small pins on the floats, and
if not close to correct alignment, the carburetors can
flood. There is NO provision for an overflow/vent for
the float bowl, as in the stock float bowls, and thus,
theoretically, it is possible for the bike, especially on
the left sidestand, to fill a cylinder with UNcompressable
fuel...which can destroy a piston and rod, ETC. The
overflowing fuel might go on the ground from a further up
carb body port, and not into the cylinder. I would
not count on this. However, the
separate floats seem to be stable for any type of
gasoline's, and MIGHT just last almost forever. There
is an article on this website on the Bing kits....
bingindependent.htm
These kits were originally sold with plastic bowls. Those bowls have been known to develop cracks, often microscopic, that cause weeping of gasoline. The latest Bing bowls are zinc metal, like the original stock bowls. They are EXPENSIVE, and NOT available from BMW (BMW carb parts prices are often MUCH cheaper than Bing's!!).
****NOTE: The old method of turning the carburetor upside down for adjusting the float level is not used any more for the STOCK one piece white floats...but it IS for these Bing dual independent floats! At least per Bing's sheets. However, by using one's finger, carefully, one can adjust the float bridge of these Bing kits, whilst on the bike...and Bing's latest sheets reflect both methods of adjustment.
So, for these
independent float conversions, here are some adjustment
specifications:
With carburetor upside down the most outward part of the
brass hinge unit, the top of its flat area, should be 10.5
mm and parallel to the base. AND...BOTH of these arms
MUST be parallel to each other. For the old model 55
carburetors this was 8.5 mm. Once in operation,
one could remove a bowl quickly, and the center area to top
of the fuel should be very close to
1-5/32". NOTE that
after first installing and adjusting one of these Bing
independent float kits, they must be
RE-ADUSTED after maybe a dozen hours of
riding. This is because the float needle breaks in,
and the effect of fuel on the needle and float. Quite
frankly, I think the BRASS also tends to change a bit,
something to do with its hardness and tempering grade I
suppose. It is important that the
spring loaded plunger on the float needle be in good
condition, and the spring inside it not sacked out, or the
mixture will be variable due to changes in the fuel level.
To adjust whilst on the bike, maintain the arms parallelness to each other, and adjust for 0.412" from the arm lower edge to the carburetor body, at the point your finger VERY LIGHTLY pressing on the arm assembly, causes the float needle plunger tip to NOT QUITE start moving upwards.
<<<<>>>>Once in awhile deposits of fuel residues will get into the needle spring and cause it to malfunction. The float needle tip also wears out. Thus, the float needle should be replaced at regular intervals, just like the stock one, and they ARE the same part....as delivered from BMW or Bing. I recommend 30,000 miles. It appears that the floats will NOT require replacing on the Bing KITS. I'll say it again: The float needle is the SAME as on the stock carburetors, so it is available, likely cheaper!...from your BMW dealership. <<<<<>>>>>
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Your stock floats are held
into the carburetor by a pin that is knurled on one
end. Those can wear, although it takes
a 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 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 ChannelLocks and
break the float pin bosses. You install the
NON-knurled end first, of course. The floats may
be 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. It is a slight PIA to install the stock
floats...or the KIT bridge...with that wee tiny wire clip
and the float needle. Just takes practice....see
below...
****That clip is not used on the models 64/32/1-20****
Restating some of the above:
The float needle lower end may have a tiny hole in it, that
the wire clip fastens to, and this end part 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 recommend HIGHLY
that you order SEVERAL of these wire clips when you order
floats and float needles, as they are SO easy to
'lose'. ALWAYS
replace the float needles when replacing the stock
float. 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.
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 atmosphere (smog, etc.) and some
with time, some with mileage. Since the kit
containing the two diaphragms and O-rings and gaskets are
about $40.00 or more, I have no objection if you let the
diaphragms go until they fail by getting a hole in them.
BTW...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. You can
purchase the individual parts too, of course. Diaphragms
seem to hold up rather 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 is all that is
available now. Some of those very early ones might
still be around.
BMW supplies a screwdriver
71-11-1-103-086 in the on-bike tool
kit. Phillips and standard ends,
reversible. NOT a Posi or Reed and Prince tip.
There are better choices, and stronger, but 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.
HINT: BMW carb
top " phillips" screws are not always really
Phillips screws, they just look that way. They
could be phillips, OR could be 'Posi' type.
The ancient aircraft tip screwdriver called Reed &
Prince works nicely on the Posi screws....as, of course,
does the real Posi. The Posi tip is
EXCELLENT for REMOVING the phillips type, if the phillips
is way tight. Generally install a phillips type
with a phillips screwdriver. If the screws are
frozen, you can try a variety of ideas, see my carb
articles. This includes valve grinding compound for a
better grip, a metal block underneath and an Impakt Driver,
etc. Tips for interchangeable-tip type tools
are available from a variety of sources, including Snap-On.
YES, the Posi IS available.
Some have installed Allen head screws at the carb
tops. They are OK, but don't overtighten, as many of
these have a very small allen and can round-out more
easily. Some carbs had common
single slot screws. BMW and Bing may be
shipping EITHER Posi or phillips screws......be sure that
your 'screwdriver' fits them, and do obtain a Posi #2 or
Reed and Prince screwdriver #2 or tip.
Remove the screws one at a time, coat the threads...and
taper...with antiseize....and
replace the screws.....you will appreciate that hint, later
on. ***NOTE!!!....BMW's
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, instead, a
common phillips!! The Bing carburetor top
screws may be Posi, or may be phillips (both Bing and BMW
seem to be shipping both types). The Posi screws
generally have some radiating lines to indicate they are not
phillips type.
Diaphragms may have a downward facing tab that fits into a
small recess in the slide itself. Diaphragms also have a
somewhat larger downward facing tab that fits in a
corresponding slot in the top of the main carburetor body.
These 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.
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 assembled the atomizer jet wrongly. In the Bing CV carb, that atomizer must stick UP INTO THE CARBURETOR THROAT:
****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 needle jet part. 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. Regarding the 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 and needle is already in the carburetor, be especially careful installing the central jet assembly.
Slides are
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
paragraph, you will be OK. When assembled correctly,
the slide, which has two holes at the 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 new-fangled slides
with O-rings...but I have NO information NOR experience
with them. They are quieter, in a few instances of
rattling noises.
***The following item is CRITICAL,
and is where I've seen folks REALLY mess up. I have
mentioned this in the previous paragraphs, here it is
again, somewhat differently:
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 hangup 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, the body of it. 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 this can, of
course, install any way they want to, as they know the
feel, do it with fingers initially, and also have another
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.
Sometimes 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. It is easy to lose these parts, so do
NOT! Remember, I recommended an old piece of
white sheet under the carb 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.
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. If you removed the
idle mixture screw, replace its O-ring, slightly coating it
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. Some late model slide needles
were aluminum...and the GROOVE wears very fast....they are
to be replaced as soon as this is noticed.
HINT: When installing O-rings, put some common
electrical tape over the sharp threads, and use a tiny
amount of silicon grease to ease the O-ring into its
groove. Remove the tape, of course.
One should remove only the necessary
parts, then spray into all the jets (pilot jet, bowl jet,
central main jet assembly) and holes with a strong
carburetor spray, and let sit awhile, then spray again in
every direction possible through those holes.
You may know that I prefer Berryman B-12, the 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's, which
MANY other spray solvents do NOT! 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 cruded up, often with 'black' stuff.
Removing the idle mixture screw and spraying
all the idle passageways with that very strong Berryman
product is a good idea. Spray three times, waiting a
bit each time. Use plain clear silicone grease, or
Dielectric Grease, from your autoparts store... LIGHTLY
on anything brass that screws into anything (antiseize is
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
smoother. DO
keep in mind that there are some VERY SMALL holes in
certain passageways and jets, and you do NOT want grease
clogging them!
Some Bing carbs use an acceleration
jet assembly in the central assembly, these parts all come
out mostly at one time, same as those carburetors
without.
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,
is helpful.
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
re-sprayed. NOTE that some gasoline's
leave NASTY deposits that are hard to remove. The
Berryman's seems OK for this, if allowed to work for
awhile.
It may or may not be a waste of time to disassemble the
enrichener (often called a choke, which it is not, it just
acts something like one). Certainly a cleaning and
VERY LIGHT silicone grease lubing will
make its operation smoother. If the rotating
disc, which has holes for jetting, gets plugged (unusual)
the enrichener won't work right. The enrichener
pieces are EASY to mix
up and get installed backwards...or left and
right. A good rule is to NEVER
do both carburetors at the same time. The
enrichener can be assembled wrongly. You
bike could ALREADY have them assembled wrongly.
It is very important that the left and right carburetor
enrichener's (misnamed CHOKES) not be assembled
wrong. Not only must the enrichener must be assembled
correctly for the 'choke' to operate correctly, but in the
BOWL, the corner jet in the well must be clean and
UNclogged, and the bowl GASKET
sealing well to that corner well jet area.
The carburetor enrichener parts orientation. The photo on the left side has a dimple on the shaft, hard to see, points to the lever barrel opening. Photo on the right has its shaft marked R, and it is from a 1978 Airhead, RIGHT side.
Here are some general hints on these enrichener parts:
The brass shafts that operate the enrichener are stamped in the inner ends, L and R for Left and Right carburetors. The late models (well after early /5 CV carburetors) rotating thick metal disc has an elliptical hole, and 4 smaller holes, one of those 4 is a bit bigger. The holes MUST be clear, NOT greased up! There are numerous types of the discs, some will not be machined with the elliptical hole through the disc.
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 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 or 2:00, I think.;;.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 right....say 5:00.
For the RIGHT carburetor enrichener unit, 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 is another way of saying all this: When the choke/enrichener lever is in the OFF position, the perforated disc on the lever arm, smallest hole, solid dimple, no airflow, faces down towards the float bowl, and the outside lever angles down towards the stop pin.
Re-said differently:
The INSIDE of the shafts are
marked L and R. The OUTSIDE of the shafts
have a dot, or a depressed tiny pinprick place, that dot
faces the LEVER.
It IS possible to install the two metal pieces that make up the LEVER, in the WRONG positions. It is annoyingly EASY to overlook this. They can be installed upside down AND reversed in position. In BOTH Left and Right, the part that has NO notch for the installation of the wire, goes onto the carburetor enrichener shaft first, with its offset facing the carburetor body. The outer part, that DOES have that notch, can be installed wrongly, flipped-over if you will. Install it such that the notch does NOT face upwards during cable operation.
NOTE that for a smooth enrichener operation, the enrichener needs to be faintly lubricated, cables good, and operating lever lubricated and if you have them, the T barrel under the tank where the one cable from bar splits into two, in good condition.
IF you are worried about using too much silicone grease, use silicone oil spray on the enrichener innards.
Whilst on the subject of enricheners/chokes, understand that in cool or cold weather, full choke, with cables adjusted properly, may be needed for starting AND, very contrary to all the 'books' nice verbiage, you MAY NEED to manipulate the throttle during cranking.
NOTE!!!! In one 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 aircleaners, BACKWARDS. The truth is that the lever must be HORIZONTAL for the choke to be OFF....and DOWN for choke ON.
The enrichener (choke) is held to the carburetor body by 4 phillips head screws. These screws are infamous for loosening. 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 and then tighten them. They CAN be tightened without rotating the carburetor, but it is typically a hassle, even with several types of offset screwdrivers. If you take the enrichener screws out, clean them and their holes, and use a small amount of blue Loctite on the threads before tightening. BE SURE that the gasket is OK....that gasket tends to get sucked in, or otherwise distorted, if the assembly gets a bit loose.
***Certainly one should not think about removing 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 those O-rings. 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-rings, DO coat them, 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, etc.
****NOTE!!!>>>>>The butterfly can be put in backwards. Do NOT!!!! That is why I previously said to mark the butterfly!..top, rear...or similar.
The
fitment of the lower edge (and the sharp shape at that
point) of the butterfly is critical at 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. If you have not marked them, I don't
have a good answer for you. NOTE that in
installing the butterflies as you slowly tighten the two
screws, you must lightly
press them, with a finger, into the main carburetor bore,
to align the butterfly...it is important that they fit the
bore very evenly.
The later enrichener (choke) control and all throttle
controls on all the carburetors, each have a return spring,
they are not the same type spring on the later
carburetors. The old style
carbs had the enrichener (choke) lever on the aircleaner
housing, and springs were not needed as the cable inners
were very stiff. The lever assembly at the 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 wee thin shim to allow smooth
action...as you do not want the nut loose. Sometimes
that area takes some fiddling with.
THREE
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 boss projection with a
tiny hole. If a spring is stretched or
misshapen, replace it. On the
old style carburetors, that stiff spring must not rub
against the carburetor, 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.
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 too) (room temperature or a bit
above helps, as opposed to freezing weather). Also on
the threads when assembling, I said FAINT,
not a glob!!! Again, I use more on the shaft
O-rings.
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. Again, if you
have the acceleration pump assembly, it is slightly
different looking. 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 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.
You MUST assemble the
central jet assembly parts in the correct order. Do
not over tighten.
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. The danger is in cracking that
central carburetor boss. I grease the threads
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
later.
Cleaning the idle system...jet, holes, etc...is important,
and the Berryman's works well, if allowed to work awahile.
DON'T bugger the end of
the idle jet with a poorly fitting screwdriver.
ON a rare occasion, 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
to drilling.
HINT: When
replacing rubber O-rings, you might have the thought that
the THREADS on the part might cut the O-ring...yes, they
could. A simple way of avoiding that
possibility is to not only grease the parts with a very
THIN layer of silicon grease....but to wrap a single layer
of any sort of tape around the threaded part, and THEN
slide the O-ring over it!
Don't fail to spray clean the jet in the 'well' of the
bowl, and the overflow tube too. I've had to poke
around at that jet sometimes to clean it.
NOTE:
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 source.
I always clean the various metal
parts with the mentioned brand of carburetor/choke cleaner
spray. For a major overhaul, take everything apart and use
a professional cleaning box 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, sometimes a cotton
swab will help. I prefer the spray by Berryman, called B-12
Chemtool, Carburetor & Choke Cleaner. This is
nasty stuff. 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.
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
match.
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 specification by moving
the needle position; 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. This is
almost always the better approach. 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 most 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, 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. Later Bing CV carbs have a screw in the top of the slide. Remove the central flat-head 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.
If the needle is aluminum, and the grooves worn, replace the needle!!...see below...
NOTE!....The SLIDE needles should be replaced at the 60,000 mile intervals I recommend, or tad sooner, with the associated needle jet. There is a particular problem with the needle material on some 1985+ models, in 32 mm size. There may be some other carburetors with this problem. The NEEDLE grooves WEAR, probably 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.
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 acceptable.
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,
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. Do them EVENLY,
with even pressure. Once the fresh sanded surfaces
are evenly fresh all the way around, that is likely
enough. Do not overdo this.
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). See the HARDWARE.HTM
article on this website, for a huge list of Roundels,
including exactly which fit nicely the small tops.
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 just at one
edge.
After making a small change...
Turn gas off. Turn gas on, lift float gently 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 below, maximum. 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 float needle.
For the KITS, the adjustment is the same, but the measured
distance is .412" from either lower arm edge to the
body.
I have information on this website ....copies, crude, but useable...of Bings sheets on adjustments of the independent floats KITS. Here is a hyperlink: Bingindependent.htm
Be gentle and careful about doing any
bending. Float level affects richness-leanness and gas
mileage.
Major tuning/adjusting the carburetors is not part of this
article.
NOTE and HINT: The band clamp at the carburetor throat inlet USUALLY should have its adjustment at the TOP...or, at least not at the bottom. That curved intake plastic tube fits in most models only in one direction. If fitted wrongly, things do not line up well. 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. That intake plastic tube can be slotted for easier use.
NOTE:
Do NOT!!!...NOT!!!!...use anything but the original Bing or
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, and MAY work
marginally. There are differences, in
material/thickness that do NOT seem consistent.
I don't know much more about this situation.
What I can tell you is that the Stromberg CD150 diaphragm
does physically fit the 32 mm Bing CV; and the CD175 does
physically fit the 40 mm Bing CV. There is ONE reason
you MIGHT want to consider these substitute
diaphragms. 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. You CAN pry that ring off (hot
water helps to avoid injuring the ring), and use the
Stromberg part, re-installing the nylon ring.
Most autoparts stores carry Stromberg diaphragms.
Additional information on Bing CV carburetors will be found at Bing CV Carburetors-2
Revisions:
to 12-07-2002: mostly
clarifications.
Through 12-09-2002: add area for upcoming float
testing; added references to Bing CV Carburetors-2, many
clarifications and emphasis items. This
version was not to be released to the website, pending more
additions.
01-30-2003: Updated many places, decided to release
to the website even though float testing has not quite
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.
Smith's article
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
10/18/2005: general
updating
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.