Fuel
Filters, Gas Caps, Petcocks, Tanks & Seats
AND.....ROUNDELS!
fuelfltrs&petcocks.htm-1
©
PETCOCKS in
general:
BMW has used FIVE TYPES of
petcocks for our airheads. Many of these are re-buildable. Usually this
means that you unscrew some knurled or slot nut at the handle area,
and you can replace a gasket that might be bad, or
clean and lightly silicon grease the moving parts. You
then have a much smoother operating petcock. On some there is a dimpled
disc, which can be repaired for a better detent action.
All the petcock's except the early /5 bullet type are similar in INternal construction; some variances, but the basics are the same, perforated discs. Early /5 were different, the rotating handle effecting gas flow from one or another port.
The early bullet-style petcocks popular on the
/5, which look like there is no way to take them apart, are sometimes
re-buildable. Frankly, I would not bother with the early bullet
styles, you likely will break them taking them apart. However,
for purists, it may be worth a try, and you can take a look at
Vech's website: http://benchmarkworks.com
These early /5 petcocks, on the other side of the handle (towards the
motor), look something like a very large
tapered round bullet. The very early types
are snapped together, very difficult to take apart without
breaking them. CAN be done, SOMEtimes.
These have a removable nipple at the bottom, inside of
which is a small fuel screen. There are three problems with
these petcocks. Because they are the Classic /5 petcocks,
you MIGHT want to TRY to overhaul one. One problem is that
they are difficult to take apart; another problem is the wear on
the left one by the choke cable touching it....cured by adding a
piece of rubber hose to the cable, a third problem is that
overhauling them is more involved. Repairing one is a bit
time consuming, but you can retain the classic look of your
/5. You have nothing much to lose, as you can always
substitute a later petcock, so here is a way to go about it::
This early /5-style of petcock
is press-assembled, and staked. To disassemble it, you must
trim away the body slightly, of the crimp area.
Do NOT remove excessive material in that trimming.
Then put the HANDLE of the petcock in a soft jawed vise, and pull
and twist the body, and it will come apart. You will
need some 1/8" thick cork to finish the job.
Most autoparts stores have some. You could use a piece of
gasket material, etc. You will have to cut the cork to fit,
and then SILICONE grease it, roll it sort of cylindrical, insert
it into the body...seam towards side...install
squarely. Grease the removed plug part and install
it...it will take considerable pressure to do this. Now you
need to crimp the area so it cannot come apart on its
own. After that is done, turn the handle (fair amount
of force probably needed) to ON position. Drill down the
main tube through the cork, and the outlet too. Blow out
the cork dust. Repeat for the reserve position tube and
outlet. Clean out, and reinstall.
HINT!.....The choke (or
enrichener) cable passes by the left petcock, and tends to wear a
hole through the petcock...so put some rubber hose tubing over
the cable. This is particularly so with the early bullet
style /5 petcocks.
NOTE: There were two types of GERMA petcocks, the handles had a sort of tab area, and there was a screw in the center of the handle. They ARE easily rebuildable.
ALL the other
styles are fairly easy to take apart, clean, and repair...typically
this is done because they have begun to either leak or are stiff
operating. Two versions of these have in-tank screens
and a separate sealing washer combination, it is best to replace
that old screen with the later bonded-metal-washer style screen that BMW offers, and then
NO separate cambric washer is then used. The reason you want to replace the
early style is that it CAN let debris through where the screen meets the petcock
base...., and forming the roundness of the screen into the petcock is necessary
whenever the screen is removed. Stated differently: You had to 'form' the lower end of the
screen into a proper round shape, then insert the screen a
bit into that cambric washer, then assemble, making sure the
screen fit into a recess in the petcock top area, and then attach
to the tank. It was a bit of a hassle to do this
perfectly. That type often had a spacer,
usually white, near the top, INside
of the screen, not a critical item if missing. The problem with
those early screens is that folks simply did not pay attention to
assembling the screen, washer, and petcock upper cavity, and the
screen then did little at the bottom, letting junk get into
carburetor. BMW
changed the design of the in-tank screen, and if you purchase an
in-tank screen, you get one with the washer now being metal and
permanently bonded to the screen. NO special sealing washer is
needed, you do NOT reuse the old washer,
just have clean surfaces and a good
grunt on that outside nut....with equal threads being engaged!!.
Some petcocks have a SMALL screen filter located IN the OUTLET. These petcocks have the outlet straight down, and have a separate smaller nut at that outlet, so as to remove the outlet stub and get to that filter. That does NOT mean that all straight down outlets have screens. Easy to find out, simply remove the hose, and unscrew the lower nut, see if a filter there...or a place for one, the previous owner could have left it out.
TWO petcocks do not have such an outlet screen
filter, these have a horizontal fuel outlet. One of these will look similar to
the late version but the threaded ring, which is still cross-slotted,
has NO outer edge knurling, but does have the internal operating 'gasket',
with the ports to allow the fuel flow, made of cork.
Change that to the rubber part
#16-12-1-235-551. GENERALLY that cork to
rubber change is for the USA and Canada shipped models R60/6
through R100S. There are sub-variations of these petcocks,
in how the outer ring appears, tightened for pressure, or not,
etc. The working face of the inner
flat side of the handle, must be free of deep
scratches.
Generally speaking, whilst the
various inlet and/or outlet screens should be cleaned, perhaps
yearly, there is no need to disassemble the petcock internals
until action is overly-stiff. THEN, except for that
cork problem, there is usually nothing to do but clean, and apply
silicone grease very thinly, and reassemble.
The outlet part, when the removable
type, is called a tap spigot, or similar, and are
available, or were, in both metal and plastic. That spigot
may have a groove in the part that fits up to the petcock, hidden
by the nut...that groove is where the filter screen fits, some
types of filter screens had to be hand-formed to fit just right,
others had stiff end structures.
Except for the early 'bullet' style petcock, the other types of
petcocks are easily taken apart, but sometimes, on the LATER, non-Germa ones, one needs a good grunt to push the
threaded 'nut' back into the body to get its threads started
properly. Some folks think this is easier by using a bench vise (carefully,
don't over squeeze!) on the NUT portion, and pushing the
petcock portion, squarely...SQUARELY!!...to
the nut. NUT here means the knurled or slot part (possibly under
a black plastic cover, which pries off). TWO types of this sort
of petcock have outlet screens.
At least one type does NOT have an outlet filter; and, for sure that one type, at least one version, has the outlet pipe facing the rear, NOT downward, unless someone reversed the L and R spigots, as some WERE 'handed'. THAT type, and some others have a TALL screen INSIDE the tank, and by removing the petcock you will see it immediately. This was a very popular type of petcock, used on the 80's and later, generally.
Always service
the fuel tank and petcocks by REMOVING the petcocks from the
tank. You NEED to see what grunge is there, clean the tank,
etc. As
noted previously: Change the
tall screen with separate sealing cambric washer to the later
one-piece bonded washer screen, and do not use the cambric washer
in that case.
If your tank is empty, you can unscrew the large nut that holds
the petcock to the tank, with a large Crescent or other
adjustable jaw wrench, or wrench from your BMW tool kit.
They can be tight. As you face the petcock, push the wrench
to the left to loosen.
That large nut tightens the petcock to the tank and at the same
time it has a reverse thread
on the petcock. Thus, when assembling to the tank, you start with
the nut in an estimated position on
the petcock. The
idea is to END UP with about equal amounts of tank and petcock
threads being engaged. If
you have a horizontal outlet petcock, it is generally better to
have the outlet facing the rear....handle
is on outside, so if yours is not, you have the left and
right one's reversed. The reason for the rear facing outlet
is to make a nicer hose fitment. This does not work out for
all Airhead models.....see how YOUR hose fits.
Once in a great great while I hear about someone
with, well, a wrong idea on how the petcock works! I am NOT
kidding here. As a general rule for piping,
material inside the piping flows when the handle points in the
direction of the pipe, NOT when at 90° to the pipe. Also,
your petcock MIGHT not be marked ON, OFF, RES (reserve). It MIGHT
be marked AUF and ZU. Please be advised that AUF does NOT mean
OFF!! AUF here means MAIN tank portion is ON! This is not as
laughable as you may think! ZU means OFF. Thus,
when the handle lever is downward, the main tank is being used,
when upward you are using the main tank and
reserve, and when horizontal you stop the fuel from
flowing.
Aside note!
Some Clymers books are WRONG on the position of the handle for
the choke
(enrichener)...the handle that is mounted on the left side of the
aircleaner clamshell on earlier models (pre-1980). When the
handle is horizontal, the choke is OFF. When the handle is
downward, the handle points in the direction of extra fuel
richness....towards the carburetor. Clymers had
this backwards!
There are two tiny diameter plastic or metal pipes
"straws" of unequal
length going upward from the petcock into the tank. When the
petcock is turned to the off position, both pipes are closed off
from gas flow. When the petcock is in the main tank ON (down)
position, fuel can flow into the tall pipe until no fuel is
above its level. Once the fuel in the tank (on THAT side
for two petcocks tanks) is at or below the tall pipe level, you get
no more fuel from that petcock in the main ON position. Putting
the handle on RES (upward) will start drawing from the reserve
portion of the tank, the short straw on that petcock, on THAT
side of the tank on two petcock models. Thus if you
wanted to, you could run on one petcock, main (down), until the
motor runs that side dry on the MAIN, then turn the other petcock
to main (down) position, and then use two more RES (reserve)
positions. Up to you how you use the petcocks.
If you have a one petcock model, you have less
options. For R80 and R100 engines at the highest
speeds for longer, rather than very short stretches of road, I
suggest BOTH petcocks be turned on, if two are available.
The petcocks were built in various outlet
positions, down, and horizontal, and there are left and right
handed ones, and all interchange, but hoses won't connect at same
angle necessarily. On the horizontal ones, the outlet is to the
rear, BUT, the models shipped to the U.S. with evaporative
emissions stuff MAY have them facing forward, if the system
is stock and not modified. You can put yours in left or
right, as fits best with your hoses, ETC.
The two sides of most of the tanks do NOT hold
the same amount of fuel for main nor reserve positions for two
petcock model tanks. These are not big differences.
NOTE: The fuel caps and venting means
for the tank varies by year/model, but it is common to have an early Airhead run out of
fuel.... stumbling, loses
power, etc......and the problem will be the tank vent...or the cap. This
is provable by loosening the cap and hearing a whoosh of air
entering, and the bike then runs OK (within 10 seconds). Stumbling from this vacuum problem usually
happens more quickly with a fuller tank. Fuel cap cork seals are replaceable. So is the black surround on the
later caps. See much later in this long page on fuel cap problems
and fixes.
If the tank is not cleaned regularly, perhaps yearly, and
especially if you don't fill up after every ride, or live in high
humidity area, etc., the tank may accumulate a fair amount of
WATER, which WILL ROT OUT YOUR TANK
BOTTOM. CLEAN THE TANK TOTALLY, at least
yearly!!! Clean the filters at the petcocks regularly, yearly is
usually OK. If a
fuel tank is very old, grungy, full of sediments, etc., I
recommend using a high pressure car wash wand on the tank insides, then wash the tank and dry it.
It is quite helpful to fully refuel before the bike sits overnight. That helps with dew collecting or moisture condensing inside the tank; which ROTS the metal tanks...yes, even on aluminum tanks.
Many folks add an additional aftermarket
filter below the stock petcock. I DO recommend that you DO
THIS. Sintered metal types are OK, as are paper
types. SCREEN
types do very little good, as your petcock already has a screen.
That also applies to finer screens, which do only very slightly
more. I prefer the paper types, others prefer
the anodized metal bodied internal sintered element types.
I like the larger Napa 7-02323 filter. The Fram G4164 will
work fine too, and both are about the right size for most
folks. Be careful with the plastic filters, it is easy to
crack the throat of these. The FRAM is NOT made as nicely
as the Napa filter, the Fram has less pleats, not well supported
internally. Napa has a 7-02357 that is smaller,
POSSIBLY 'adequate' for dual petcock use. The Napa
7-02323 and G4164 are similar, and are actually replacements for
early Volkswagen filters, VW ZVW262101....but are also used on
many small garden engines, and so on.
NOTE: The 7-02323 is very
similar to the slightly cheaper Napa 3011. The 7-02323 is
part of the Napa Marine line of products, and has MORE pleats,
and somewhat better made. The 3011 has less pleats.
Either will work fine. Sometimes these various filters are
seen withOUT markings for which end is input, which end is
output. The input end is the end that fills the OUTER area,
the output end is the connection to the filter INsides; but this
is HARDLY critical!
NOTE! For whatever
reason, Napa, and see www.napaonline.com,
has changed its numbering system slightly. If trying
to see a photo or? of the Napa filters, if their search engine
does not display a 7-02323, try entering it as 702323....and it
may come up as SME-702323 or even SME702323. Same for the
702357. Don't know about the 3011.
Note: Other filter numbers that seem adequate
are: Baldwin BF-989; Wicks 33-027; Wixom 33011.
Aftermarket fuel filters, expanded
information:
These are fairly popular, and are typically installed just below
the stock fuel spigot(s)/petcock(s). Most of them flow plenty of
gasoline, until they eventually clog up, which may be months or
years (some absorb water, a nice thing, and clog from that, a
good thing actually). Notice that whether the metal
internal type or the paper type, they almost always have an ARROW
telling you the direction of gas flow.
The arrow does NOT point to the tank! The really teensy tiny
small plastic filters with the pleated paper elements are not so
good, and CAN have some problems. Slightly larger ones are mostly
OK. These filters work best VERTICALLY. DO NOT
fail to replace these filters now and then and do NOT fail to
clean the tank, and clean the petcock filters now and then.
Note that ALL these in-line filters do a vastly better job than the in-tank screen, which is ALSO NEEDED; whose purpose is to capture LARGE sized junk. The aftermarket external filters are a big help because it takes hardly anything as thick as a human hair in the carburetor to cause problems. A few aftermarket filters have cleanable elements. Please note that if fuel flow decreases enough, your engine will run lean...and potentially hot, or at least stumble some, and a lean running engine can be harmful to your bank account!! NOTE: If you install aftermarket filters, do carry some short piece of hose, clamps, or whatever YOU need, to enable you to remove a filter if it should crack and leak, or, you have some other problem. PLEASE be careful to do a neat installation, and think about the long term. You do not want a faulty installation allowing gasoline leaks. In other words...whether you use these aftermarket filters or not, consider what might happen, 300 miles from nowhere, if you have a leak in a rubber hose...or a filter leaks, breaks, whatever. Carry a piece of hose, perhaps a clamp, perhaps a way to plug one side if you have a dual petcock tank.
Straw length changes: I do NOT recommend shortening the short straw, to enable a very slightly more amount of gasoline to be used before the tank runs dry. If you DO shorten the straw, do NOT!!! eliminate it entirely!!!
Removing hoses: Sometimes you can pull the hose off with your hands
without
excessive force, but often they really stick well, although
using one hand on the end, and pulling on the hose, MIGHT
help. The official BMW hose, whether
the old silver braided stuff or the newer black metric gas line,
is slightly less in diameter than American fuel line...and, being
smaller, fits the cross area of the airbox easier.
HOWEVER, all fuel line of any type tend to really stick to the
outlet nipple pipes (besides making a good fluid seal), and no
hose clamp is needed, except with SOME aftermarket in-line
filters. Do NOT use ANYTHING but
GAS/FUEL line! Some
folks put a pair of pump-pliers onto the hose near the petcock
and give a mighty pull. That tends to tighten the hose!...as it
stretches the rubber, which is reinforced with fibers....just
like the old Chinese finger-pull toy.
Better to use a very broad flat tool of some sort and push the
hose at its end, whilst gently pulling on it. I got pretty anal
about this once and made a tool to do it. Was just a
U-shaped piece of metal. Another idea is to put a large
diameter 'fender washer' onto the outlet nipple before pushing
the hose onto it...that way, when removing the hose, you both
push on the washer whilst gently pulling on the hose....and the
hose almost always easily comes off....no Chinese finger toy problem here.
BMW does not use fuel line clamps on Airheads.
Fuel flow of 350 or more cc per minute is
adequate for our airheads. Measure it by removing a
carburetor bowl, and letting the fuel flow into a
container. Avoid sparks and fires!
One should regularly drop the carburetor bowls
and empty them out, even flush the bowl jets, pipe, etc., with
something STRONG, like Berryman B-12 CARBURETOR AND CHOKE spray,
and replace the bowl gasket now and then. I recommend
emptying the bowl of junk, water accumulates there, every few
months. Junk can rise and get into the idle pilot jet, which has
an exceedingly small hole....and junk and water can mix and tend
to plug the tiny corner well bottom jet, and then the enrichener
won't work properly. A bad bowl gasket, especially at the enrichener down
pipe area, can make your
enrichener (choke) work BADLY. The central jet
assembly in the CV carburetors has a tendency to collect black
grunge...remove the entire assembly and clean it now and then...and be careful upon
reassembly not to overtighten, nor
tighten the assembly against the needle tip....!!!.
Parts fit properly only one way.
GAS CAPS:
From the /7 onwards, BMW changed
to a screwable, removable, fuel cap. These
caps have caused no end of grief.
There are TWO basic types of these screw-top caps. One type has a BMW
logo, and the later type has NO logo You MUST determine the difference,
before dealing with one that is not functioning! The
earliest versions have a anodized finish and a BMW
LOGO!!......the later ones do NOT have that BMW logo on the top.
Both caps have a replaceable plastic 'rain skirt', that fits into
a groove in the cap cover part..
It is possibly better to not key-lock your fuel cap and certainly BEST NOT TO tighten them to the ratcheting point. The ratcheting is NOT the same as car type caps, and is NOT to be used for the same purpose! Frankly, I have never FULLY figured out why BMW designed the cap the way they did....as it is not the same function as every other vehicles ratcheting cap! If you regularly tighten the cap to the ratcheting (really a beyond-locking-point) point, you will eventually strip the ratcheting parts and have fun removing the cap. I understand you may want the cap locked. The BMW ratcheting gas caps will wear out and cause you problems if you insist on ratcheting them. The plastic pin jumps into and out of 4 holes when you do that, and wears it badly. If you lock your cap, do not tighten it firstly to the point it ratchets.
Screwing inwards and
tightening the BMW caps to the point that they RATCHET, which is
WRONG..... can slowly deteriorate the internal ratcheting
mechanism, and the cap may then seem totally non-removable, and just spins
in place:
There are several methods of removing the caps...so pay attention!
1. ANY of these caps can be DRILLED, through the cover, and then you lock the top and bottom sections together. This can be done with a 1/8" drill, and use a long shank from a 1/8" pop rivet...or, even a nail. If you drill in the handle area, or at the hinge area, the drilled area will not be seen, and the cap can be left that way,...the only problem, if any, is that the lock won't work. You can drill (NO electrical sparks, please!) through the LOGO if the cap has one, or, under the handle or hinge area. About 7/8" ...or 15/16" ...from the center of the cap is about the right distance. You can drill under the wide area of the handle, and countersink the drilled area, and use a long countersunk head screw as the method of locking the top and bottom of the cap together. If you drill the cap downward, through the top, into the metal, through the open space, and down through the lower metal, you will need a several inch long drill bit. My suggestion is that you drill the cap with a drill size that fits a nice convenient nail, and you can use the nail permanently in the cap, or use it as a new type of cap key.
2. If your cap has the LOGO, and you do NOT want to drill it, you can grab the plastic skirt with pliers, and slowly pull it sideways away from the cover.....keep pulling (it stretches), until clear of the cap and lift and pull until it comes off. You will now see that in the groove that this plastic skirt fit into, there are THREE holes, 120° apart. Take a nail or piece of broken coat hangar wire, etc., and insert a bent tip end of that into one of the holes, and lift on the cap cover, whilst gently turning it and pushing the wire inwards. You are 'feeling' for a dimpled area, and when found, you have the parts temporarily locked, and can UNscrew the cap.
3. If your cap does NOT have the LOGO, and you do not want to drill it, the body ridge snaps into a cover groove, and you might try pulling the cover off the body. One method of getting the cap to unscrew, is to wrap a very strong belt or rope around your waist, through the cap handle, and stand on the pegs; and, holding with a quite strong upward force, try to unscrew the cap. Don't go too strongly on this, unless your purpose is to try to break off the top portion, not just unscrew the cap. I suggest that you use a fair amount of force, but not handle-breaking type of force...so you will protect the tank from bending this way. Do NOT do this, or only much more gently, with the LOGO cap....as the cap cover has a rolled metal edge, is very strong, and you might bend the TANK before the cap pops off (that happens under extreme force).
Here
is another idea to consider:
If you
get the cap off, without drilling from the top, then don't,
generally, try to 'fix' the later model screw caps
internally. Simply drill, starting
from the fuel side of the cap, a hole, through the SECOND
metal layer. That means drill through the bottom of
the cap, and continue until you drill through the next
layer. The size of that hole is unimportant....well,
relatively. Hole of about 3/32" is OK, although
smaller will also work. You can now lock the sections
together.
NOTE!!....the above information is rather limited. For a fuller treatment, with photos, see the BMW Riders Association publication called On The Level (OTL), dated April 2006. An article by Anton Largiarder is quite informative on the later screw caps....including information on changing the locks, ETC. This information MIGHT also be on Anton's website......read that article...and also see mine:
RE-keying
the fuel caps; lock cylinders, purchasing caps/locks/keys.....and
more .....:
(see article #75 for LOTS more gas cap lock
information): locks_caps_etc.htm
SOME info:
The 1977+ fuel caps (these are the
ones that screw into the tank) create lots of questions at
times. Here is some information, but you may well have to
ask your local BMW dealer about the present status of these
items. Frankly, you may need to find a parts-person willing
to spend the time with you on this, particularly if you want to
order a cap with a key that matches your other bike key(s).
It is possible, sometimes, to carefully remove the old lock
cylinder by drilling it out and removing the bits. There is
another way of doing this, and it has been done in various ways,
including doing it mostly downwards, then adding a sheet metal
screw and prying the lock upwards.
Usually, folks want their 'new'
cap to have the same key as their ignition/bags key. This
can't be done on early caps by the normal means of re-keying as
done with the bags, as the fuel cap lock is a plastic
affair. I would not be surprised if BMW changes the design
so it CAN be rekeyed by the normal method of taping the body
(keep pins and springs from flying), inserting OLD key instead of
the new key, and filing down the protruding pins (NOT the last,
END, locking pin!!)....then inserting the lock unit.
For the cap with a LOGO, the cover is held to the body by a
crimped lip...you can undo that crimp, remove the body, and with
a new cap, pry the body out of the cover, and extract the plastic
lock cylinder assembly. By thinking this over, you can see
that you can transfer an old lock cylinder to a new cap.
When a key is in the lock, and turned, you can see a small
release point in a small opening in the plastic. PUSH that
part inwards with a tiny tool, and then you can withdraw the key
lock assembly! If the key lock assembly is not
broken, cracked, etc., you can clean it, lube it with some light
grease, and insert it into your NEW cap, by aligning it and
pushing it into the cap....you MIGHT need to turn the cap via a
bit of force, to push it all together....to allow the lock to
fully install. Once installed, it is permanent.
Some caps have smog/vapor 'enhancements'. Some remove the vapor
items entirely, and plug the vertical pipe in the starter motor
area. Some remove the tank flapper valve, some remove all
the solenoids, etc. YOUR choice. The caps for that
system are different....and say SHED247. Do not use
the wrong cap, unless plugging.
The black standard cap is
51-25-2-307-125
The plastic trim ring is not included with caps, and is
16-11-2-307-360
The standard cap with a lock and a key is 51-25-2-307-168
The SHED caps are available in both black and chrome. The
black one is 51-25-2-307-140; and the chrome one is
51-25-2-316-185. You won't believe how costly all these
parts (except the ring) is.
A new lock cylinder is
51-25-307-166. The key will not fit your
other locks. The original keys for the
motorcycle included stamping of a number on the key, a knockout
part that is; and also a small tag came with the keys, with a
number on it. If you supply the number to the dealer, he
may be able to order a custom-keyed cap for you. I say MAY,
because you have to have a knowledgeable parts person, AND, this
number may no longer be available from BMW. Custom
keyed cap: 51-25-2-307-173. A new cap
with new cylinder and 2 keys (obviously not keys that match your
other bike keys) is
51-25-2-307-168. Caps without lock
cylinders are no longer available; unless a dealer happens to
have one.
FRANKLY, because the cap internal plastic pins wear from
misuse (ratcheting), I do NOT recommend even trying to re-key an
old cap!!! I would ONLY get a brand new custom keyed cap,
which will take time to order and get it, or a new cap with lock
and keys. Custom caps used to cost the same as
a cap with lock that had no common keys to what you already
have. There is also the transferring of the old lock, you
can also consider that.
Fuel/GAS
TANKS>>>>>AND SEATS:
It is not at all uncommon for folks to swap various
tanks and seats. Here are some basics:
The /5 and /6 SEATS are LONGER than the /7 seats.
The /7 SEAT will be OK with a /5 or /6 tank.
The /7 tank can fit a /5 or /6, but modifications are needed,
otherwise it is rather ugly.
There
are differences in how the various seats mount.
Early seats had the hinge portion screwed to the seat, with allen
screws, and if they rust-out, can be a bear to remove
them....making it a bear to get the seat off the bike.
There are variations.
It is not uncommon for the area around the seat portion of the
hinges to rot out, from moisture accumulation. This can be
fixed almost always by making up small flat plates, in a U
configuration, and having them welded to the seat bottom.
This CAN be done with the upholstery intact, if wet cloths are
used. It is a good idea to drill the recess area of
these hinges in any event, whether during welding repair...or
stock....to allow any accumulated water to go
downwards.
Use antiseize compound on seat screws.
Don't depend on factory printed information on
the tank capacity.
MORE ON TANKS:
Because BMW has a month-long vacation shutdown
(the factory is closed in August), a year model could have been
produced at the end of the prior year.
That being said :::
In 1970 and 1971 there was the larger capacity 6.3 (6.0 per BMW)
gallon tank, it was special orderable for the 1972 production
year...and a few, I think, were produced that way for 1973.
1972 had the smaller capacity tank, almost exactly 1 gallon less
capacity.
The 1970 and 1971 fuel caps had the hinge at the FRONT; but in
1972 and 1973, it was at the rear.
The 1973-1/2 (when BMW also switched to the long wheel base) had
the cutout underneath for the hydraulic master cylinder that
appeared in the 1974 /6 model.
The standard capacity 6 gallon tanks had black knee pads.
In 1972 the Toaster tank was, however, standard for the U.S....withOUT
pin striping.
Early in 1973 production there were not only the toaster chrome
panels, but also pin stripes.
Rubber pads were available for the small tanks...AFTER the chrome
panels were discontinued.
Authorities tanks (Police) look like the /6 tanks, with the
rubber pads too....but the top has a lid.
/5 tanks have screwed-on Roundels.
Here is a link that covers a whole
bunch about those early tanks:
http://5united.net/html/fueltanks.htm
Tank capacity varied considerably in later models. You can contact me for information, or see your Haynes or Clymer's manuals.
When BMW publishes a fuel tank capacity, you ADD the tank and reserve amounts to get the total amounts.
Revisions:
10/05/2003: revised to incorporate all previous changes and
updates on the petcocks and cap removal methods
03/30/2004: spelling typos, emphasis
03/31/2004: Final version, and add Fram filter number,
minor clarifications, eliminate SOME redundancy, upload.
04/04/2004: add overhauling Everbest information.
07/01/2004: Slight updates, some clarifications
08/26/2004: update for venting, modifications, tanks, seats
09/07/2004: add tank capacity information
09/12/2004: updated, added links
10/01/2004: fix waste...waist typographical error
10/29/2004: update numbers, clarify caps and keys details
03/05/2005: Revised extensively to have information in
better order, as things had been overly-repeated and much of the
text was choppy. I added some
comments on filters and the gas caps.
11/09/2005: red note on Napa filters numbers.
03/23/2006: more information on the Napa filters.
04/18/2006: Revised, for clarity, information on the gas
caps; minor in other areas.
11/07/2006: clarifications and emphasis
11/21/2006: add roundels information
02/01/2007: Remove Roundel information, as it will be
updated and expanded in article 68.
07/28/2008: Revise a lot of the article strictly for clarity. Also
add not on Anton's article in OTL.
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