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Fuel filters, petcocks, tanks, fuel flow amounts, re-fueling,
choke lever marking on clam-shell models; fuelhose material, ETC.


Copyright, 2014, R. Fleischer


PETCOCKS in general:

EACH petcock is fastened to the tank by both right and left hand threads.  That is, as you rotate the large "nut" CW (facing from below), that tightens the nut to the tank while at the same time it brings up the petcock, loosening its thread numbers there. Thus, the petcock large nut has to be FIRST engaged the proper amount onto the petcock BEFORE screwing it upwards to begin to engage the proper amount of tank threads.  You will have to fiddle with this a few times, until you get the right amount of petcock and nut threads assembled, to start...and finish.... the petcock-to-tank fastening process.  Once you learn, it is easy.  You want approximately the same number of threads engaged on both the petcock and the tank.

BMW has used numerous petcocks, but there are FIVE TYPES of petcocks normally seen for our Airhead motorcycles.  All except the /5 bullet types are rather easily re-buildable. Usually this means that you unscrew some knurled or slot "nut" at the handle area (after removing a black trim cup, if it is there on your version), 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 are one or two dimpled discs, which can be repaired with a shaped punch, lightly hit, for a better detent action.  These discs have a locating tab.  They confuse some folks, so take notice of how assembled as you take things apart.  You CAN figure it out, if you forgot to take notice.

There is a version with a gasket you MAY need to make, I will get into all these versions in this article, more or less anyway.

MOST of 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.

NOTE:   Some have been able to force-twist the /5 Everbest petcocks apart for repairs.
Here is a link to an article:

NOTE:  Here is a link to a parts kit:

NOTE:  Here is a link to a guy with an Ebay store.  He can, I think, service yours; or, has cork gaskets, ETC:

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, while I would not bother with the early bullet styles, for purists, and originality purposes, it may be worth a try, and you can take a look at Vech's website:  Where he has some decent information on how to rebuild one.  The problem is finding the article.  Vetch's website is generally not set-up for internal hyperlinks that are easy to get to.

However, this MAY work:

Here is a link to Bing Agency's petcock page, useful for the photos, etc.  BMW dealership prices may be LESS.

ALL the petcock styles except the bullet nose /5 type are fairly easy to take apart, clean, and repair...typically this is done because they have begun to either leak or are stiff operating.  

****Petcocks that use CORK inside for the active element can sometimes be reclaimed to good operating condition, after, say, being dry for years, etc., by simply soaking in very hot, even near boiling, water.

Here is a sketch of the original slash-5 bullet petcock:

NOTE!   On these /5 bikes with the above petcock, the CHOKE cable tends to rub
the underside of the bullet area.  That cable can, and has, been known to wear through the
  petcock!  I suggest you add a piece of rubber hose over the cable where it might rub the petcock.

These early /5 petcocks, on the engine side of the handle, look something like a very large tapered round bullet.  They are snapped together, and it is difficult to take them apart without breaking them. This CAN be done, SOMEtimes.   They have an easily removable nipple at the bottom, inside of which is a small fuel screen.   Because they are the Classic /5 petcocks, you MIGHT want to TRY to overhaul one. 
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:
The 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 overhaul job.   Most auto-parts 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 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.

NOTE:  The original "straight" type petcock used early-on after the bullet petcock is no longer available from BMW dealerships.
Check out this website page for availability of that type: Series 2 valve Twin


ALL the petcock styles except the bullet nose /5 type are fairly easy to take apart, clean, and repair...typically this is done because they have begun to either leak or are stiff operating.  

****Petcocks that use CORK inside for the active element can sometimes be reclaimed to good operating condition, after, say, being dry for years, etc., by simply soaking in very hot, even near boiling, water.

There are two types of GERMA petcocks, and a couple of other types too. Some versions have in-tank screens.  For the IN-TANK tall screen type, a separate sealing washer is used at the screen bottom where it fits into the top of the petcock and it is best to replace that old screen with the later bonded-metal-washer style screen that BMW offers.  NO separate cambric washer is then used.   The reason you want to replace the early style screen is that it CAN let debris through where the screen meets the petcock base...., and re-forming the roundness of the screen where it fits into the petcock was also typically necessary whenever the screen was removed.    Stated differently, y
ou had to 'form' the lower end of the screen into a proper round shape, then insert the screen a bit into the cambric washer, then assemble, making sure the screen still fit into the 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 petcock 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 'screening' 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 will now, or should!...get one with the washer being metal and permanently bonded to the screen. NO special sealing washer is needed, that is, you do NOT reuse the old washer, you do NOT USE IT or any, at all.  

Have clean surfaces and a good grunt on that outside nut....with equal threads being engaged.  This applies to all petcocks when installing them.

Most other petcocks have the screen IN the outlet, remove the outlet part to see and clean it.  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.     The outlet, when the removable type, is called a tap spigot, or??, and they are available, or were, in both metal and plastic.  Guess which one does not like to be bent sideways when removing a hose?  Any 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.

I cannot emphasize more that you should ADD an aftermarket filter between any petcock and the carburetor.  More later in this article.

TWO types of petcocks, and these are generally the last petcock versions, do not have an outlet screen filter, these have non-removable horizontal fuel outlets so there are NO nuts on the outlets, the outlet spigot is part of the casting.   One of these will look similar to the late version but the threaded ring, which is still cross-slotted, has NO outer edge knurling, HAS a radial slot and has the internal operating 'gasket', with the ports to allow the fuel flow, made of CORK.   Change that to rubber part #16-12-1-235-551.  The cork can swell and make the petcock stiff to operate, and it can also shrink, and cause leaking.  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 last version of these had outer edge knurling and had the rubber part AND a rather stiff coil spring, and seals better.

***These horizontal outlet late style petcocks are HANDED, that is, there is a left hand side and a right hand side.  This information is hardly noted anyplace but here by me, >>>as is why TWO right sides are used on some bikes.  When installing to the fuel tank, if you install these petcocks so the OUTLET is pointing REARWARDS, then the curve of the fuel hose will be much nicer, shorter, and the hose might last longer.  In mid-1980, and later, BMW incorporated a tank fumes solenoid valve and a fuel flow solenoid valve.  These are located on the cover that fits over the starter motor, and there are then holes in that cover for hoses, etc.   Because of this, BMW elected to use TWO EACH "Right Hand Side" petcocks.   If you remove some or all of these solenoid parts, you may want to purchase a LEFT hand side petcock, which COMES with the filter screen.

Generally speaking, whilst the various inlet and/or outlet screens should be cleaned with your yearly tank cleaning, there is no need to disassemble the main petcock internals until action is overly-stiff.   THEN, except for that cork mentioned well above to be changed to rubber, there is usually nothing to do but clean, and apply silicone grease very thinly, and reassemble.  Obviously you do not want so much grease that you plug the disc holes. You DO need the grease on the handle flat area and the face of the 4 hole rubber this very sparingly.   Silicone grease may be called Dielectric Grease, at your AutoParts store....and it has many uses on your motorcycle.

Except for the early /5  'bullet' style petcock, the other types of petcocks are easily taken apart, but sometimes, on the LATER, non-Germa ones,  it is a bit of fun to  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!! the nut. NUT here means the knurled or slot part (possibly under a black plastic cover, which pries off).

For the petcocks with or without a black plastic cover around the lever area, this will probably apply:

Slowly remove the black cover. Pry evenly, all around, a bit here, a bit there. You can use a small piece of wood or plastic, or? to avoid marring.  You might want to put the whole petcock in moderately hot water, and use a wood or plastic tool.  The water will soften the black plastic cover, expand it a bit, and make it easier to remove....and the plastic/wood tool is less likely to gouge or mar the material.  There have been instances of loose caps, where someone has glued it to the petcock, just be aware of this, as it may take more work to get the cap off, which is needed to remove the handle and innards.

Underneath the plastic cap you will probably find a sort of knurled edge that must be gripped in order to separate the metal cap plug from the body.  I made a special tool for this about 30 years ago, can't find the darn thing right now, but you CAN grip the edge in a vice, and then rotate the rest of the petcock around it. It is better if you had some ROUND JAWS, perhaps from a good drill chuck, or a lathe chuck.  The black outer cap hides your messiness, but why not do the job carefully, with thoughts of not marring the metal?

My present method is to use two pieces of BRASS or ALUMINUM, which is soft, and works well with the petcock knurling, in the vice jaws. It can be done so marring the knurled 'nut' does not occur.   NOTE that it is not uncommon to see a petcock that has not been serviced in a very long time, and has been, perhaps, exposed to moisture or near the seacoast, and the knurled ring nut will not remove, or not hardly easily.  I highly suggest you heat the petcock to near water boiling temperature, and then remove it from any heat source, and place the entire petcock into a container that has a reasonable amount of very thin but warmed penetrating oil.  You want the penetrating oil to get into every part of the petcock and I work the lever a bit, then let it sit for a day, then work the lever again. I do this every day for about a WEEK.  After that, I can usually remove the knurled nut in my vice, using brass or aluminum protective jaw facings.
Some versions use a 'nut' with slots, and you can improvise for that.  I made a tool.

Pay attention to any indexing disc(s) inside, and how arranged.  Which side fits the other side, where and how the tabs fit, which disc goes back first, when re-asssembling.

Most of the time I have found the rubber disc with the 4 holes simply in need of a cleaning (with the rest of the petcock too), and then I reuse them, with a faint light...LIGHT!...smear of common dielectric grease (a silicone grease) on the rubber, and all the moving parts actually. There isn't anything in any of 'the books' about overhauling them, AFAIK.  Occasionally the dimple that locates the position has worn, I normally just forget about it, I can tell when the handle is fore, aft, up, or down! ...I don't need a click to tell me!         You can reset the dimples though, with an appropriately shaped punch.  When re-assembling, push the body onto the 'nut', not the other way around!... as the spring is very stiff.  I do it with the 'nut' again clamped in the softer vice jaws,........ otherwise you need leather gloves or your fingers will not like the knurling.  Before assembling, be sure you have faintly lubricated the handle flat and the rubber disc, and the spring, and inside the metal cap, with silicon grease.  If you do it all as I say, you may go MANY years before having to repeat the cleaning/lubing.

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.  

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 from the side of the motorcycle, push the wrench to the left to loosen.

As explained much earlier in this article, 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 ~ equal amounts of tank and petcock threads being engaged. 

****Now and then I hear about someone with the wrong idea on how the petcock works.   As a general rule for all plumbing and piping, flow occurs when the handle points in the direction of the pipe, NOT when at 90 to the pipe.  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 (closed).
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.  HORIZONTAL IS OFF!

Some Clymers books are WRONG on the position of the handle for the choke (enrichener) ON CLAMSHELL AIR CLEANER MODELS.  That means pre-1980. When the clamshell handle is horizontal, the choke is OFF.  When the handle is downwards from horizontal, the handle points in the direction of extra fuel richness....towards the carburetor.   Clymers had this backwards!  Clymers wrong information has obviously caused problems with starting and running.

There are two tiny diameter plastic or metal pipes "straws" of UNEQUAL length going upward from the petcock into the tank. Once in awhile these are replaced due to cracking on the plastic ones or they are broken, etc.  The TALL one is for the regular main tank outlet, NOT the RES outlet.  The short one is just tall enough to keep bottom rust and water and other crap from getting into the petcock on the RES position. SOME have shortened it, by half is OK, it is NOT OK to remove it entirely. You will hardly gain much additional usable fuel, and you may get tank crap into things, including the petcock and maybe the carburetor. 

When the petcock is turned to the off, horizontal position, both tiny pipes are closed off from gas flow. When the petcock is in the main tank ON (down) position, fuel flows from the tank into the tall pipe until no fuel is above the tall pipe 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. Putting the handle on RES (upward) will start drawing from the reserve portion of that side of the tank.   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.   I recommend using both petcock's ON, for 1000 cc models. If you have a hotted-up motor, and a single petcock tank, you might consider enlarging the hole through the petcock, for additional flow at wide-open-throttle. I have even done that to the straws!
For a modified engine, if you have a single outlet port fuel tank, you probably should change to a dual-port type, OR, modify the petcock on the single outlet tank. The stock single petcock will not flow enough fuel at extended W.O.T., particularly on the R100 engine. Careful drilling and modification of the petcock will work well. While you CAN retain the in-tank thin tubes leading upwards from the petcock, by drilling them out a wee bit, that is not easy, and, the best thing is to remove them, drill the petcock a fair amount larger, all the way through, and fit larger inside and outside diameter tubes to the petcock.   You can try drilling the petcock for a slightly larger straw, or reaming/drilling the existing straws.  A small change is a large change in flow.  Be sure to measure the improvement at the carburetor (bowl off, measure cc per minute or shorter period).  For the one-petcock fuel tanks, modifying is almost a must, for the R100 engines, and not modifying is marginal for WOT for the R80 engine size.  A few hundred cc per minute per carb, measuring with BOTH carbs float bowls off, is a good idea. If you have to, drill out other items, including filters, T adapters, etc. Remember:  a SMALL change is enough in diameter.

The actual length of the stock petcock 'straws' themselves is not the same between all models. The dimensions I show here are PROUD OF THE SURFACE THE STRAW IS PRESSED INTO!  The straws can be metal or plastic. The diameter of the straws is approximately 0.215" (5.46 mm), but that varies a bit. You can usually use 7/32" copper tubing available at hobby shops. If you need to, sand the end area diameter of the metal straw you purchased, and SLIGHTLY chamfer the down side very end ...both for ease in assembly and proper fit. The stock length (proud of the surface) of the SHORT straw, is 0.935" (23.75 mm); and 3.27" (83 mm) for the TALL straw. Yes, you CAN shorten the short straw and gain a SMALL amount of usable fuel. My advice is to NOT eliminate that short straw, certainly not below 3/8" proud of the metal. You will need to add a small amount to these various lengths for the straw itself, as they are pressed-into the petcock.

For tank capacity, see your owners book.   Understand that the USABLE amount of fuel is LESS than the rated capacity. Few of you will be, or should, fill the fuel tank to the very brim, where no more can be added.  Fuel capacity is not what is in the books and this particularly so on the later tanks with the fuel restrictor metal flap in the tank filler area.
When BMW publishes a fuel tank capacity, it is the capacity of the tank were able to completely fill it (which you can NOT, unless modified, on the later flapper-equipped tanks).   For modifications to caps and tank necks, see my article on them:

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.  I have seen differences of 5 to 8 miles, sometimes nearly twice that, of riding on just the RESERVE.    I have not made quantity measurements.  You will hardly gain much, by shortening or removing the petcock short straws.  I am OK with a slight shortening, especially if you have aftermarket filters below the petcocks.
For high speeds I suggest BOTH petcocks be turned on, if two are available.  This helps with possible fuel flow due to bubbles, etc. This is especially so for the R100 engines.    For an extreme case example, if you were running at wide-open throttle doing a high speed run, and managed to get to the rated 124 mph that some Airheads are rated for, you might need a gallon of fuel in 7 minutes.  You can measure the maximum possible fuel flow into the carburetors ....have fire extinguisher available!... in the following way, and measure the real world situation, via their own restrictions of the float needles and seats, etc.:

Put a container for fuel under each carburetor, remove the carburetor bowls.  Turn on both petcocks and see if you can get 16 ounces of fuel into each container in 2 minutes or less.  That is the minimum required.  Yes, a cup a minute, or, around 1/4th liter.  HOWEVER, for practical reasons, most will measure one carburetor at a time.  My personal criteria is that a Fuel flow of 350 or more cc per minute is adequate for our airheads.   I suggest that you have a MINIMUM of 8 ounces per minute per carburetor, both ON if you have two.

Repeating what is well above:
If you have a single outlet port fuel tank, you probably should change to a dual-port type, OR, modify the petcock on the single outlet tank.  The stock single petcock will not flow enough fuel at extended W.O.T.  Careful drilling and modification of the petcock will work well.  While you CAN retain the in-tank thin tubes leading upwards from the petcock, by drilling them out a wee bit, the best thing is to remove them, drill the petcock a fair amount larger, all the way through, and fit larger inside and outside diameter tubes to the petcock.  Be sure the filter can flow enough too.

Ideally, the measurements are taken from the carburetor, float bowl OFF, so the measurements include any petcock restrictions, fuel filter restrictions, etc.

Failure to continuously flow fuel can be a tank venting problem (or, with the fuel cap).  Especially on SHED models.


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.   Water comes from the fuel itself, and most comes from inside the tank walls condensation, as the fuel and tank cools, when you park the bike.  This is particularly true in high humidity areas, where you can see dew on the tank, seat, etc., in the morning.  It is very important to clean the tank of water, or it WILL rust out at the bottom!

CLEAN THE TANK TOTALLY, at least yearly!!!  Clean the filters at the petcocks regularly; replace the aftermarket pleated paper filters when flow lessens noticeably.   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.    Rust can be treated with phosphoric acid mixture (or the tank relined, which is a HUGE labor-intensive chore).

It is helpful to fully refuel before the bike sits overnight.  That helps with dew/moisture otherwise condensing inside the tank on the walls that would not be covered by fuel.  The water will condense into globules, fall to the bottom and cause the metal tanks to rust or rot out...yes, rot, 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.  Thia also applies to finer screens, which do only very slightly more.  

I prefer the paper types of aftermarket filters.  Some others prefer the anodized metal bodied internal sintered element types, most seem OK.  I like the larger Napa 7-02323 filter. It is plastic-bodied.  The Fram G4164 will work OK, 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, but I recommend the larger one.   The really teensy-tiny small plastic filters with the pleated paper elements are not so good, and CAN have some problems.

All these plastic bodied filters work best VERTICALLY, but are OK horizontally, but have less hose and vibration strain on the plastic if used 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.  If your tank is fairly clean inside, you may get 20K miles on these filters before they need replacement.  The clear plastic ones, depending on make and model, sometimes can visually show you if they are getting clogged, by looking at the paper pleats, and any 'crap' sediment.

The Napa 7-02323 and G4164 are similar, although not so in quality, and are actually replacements for early Volkswagen filters, VW ZVW262101....but are also used on many small garden engines, etc.   A.C. filter GF453 will work, but it really is too large, its diameter is nearly 2"; over-all length almost 5", and its stubs are single step with bump, and 1/4".  I recommend against this item and its size unless you have to use it, or have a very deteriorating tank.

NOTE:  Many filters have a nice feature: The input and output stubs are dual-diameter stepped, so the filters will fit whatever hose you are using.

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 OK. 

SOME filters have arrows pointing in the direction of fuel flow, but more often filters do not have markings for flow direction, that is, for which end is input, which end is output.  The input end, which goes towards your fuel tank petcock, is the end that fills the OUTER area of the filter.   The output end is the connection to the filter element INsides.   This is NOT critical on most types of filters, although most that ARE critical ARE marked. 

NOTE!  For whatever reason, Napa, and see, 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 fine are:   Baldwin BF-989; Wicks 33-027; Those two are METAL filter bodies; there is also the Wixom 33011.

Reasonable quality aftermarket 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, even though, to YOU, it may seem very small, after all, it had to pass through the screen in the petcock assembly...assuming the petcock and screen was properly assembled. 
NOTE that the tall filter screens used in many of the 90 degree petcocks, I mean the screens that stick UPwards INTO the tank, and fit over the two tiny pipes of the petcock, were originally a screen you formed the lower end of, with your fingers, to fit inside the cambric washer.  This was a poor system, and larger, unscreened particles, could often get by the screen filter, where it fit into the 'cavity' of the petcock.  A later version of this screen part is now sold by BMW, the old style NLA.  The new style has eliminated the separate cambric washer, in favor of a BONDED METAL washer.   I suggest you install the new type of filter screen, and toss the old cambric washer.

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, such as the mentioned sintered types with removable ends. 

Note that if fuel flow decreases enough, your engine will run lean and potentially hot, might stumble some, and a lean running engine can be harmful to your bank account!!   That is one of the reasons I prefer you NOT use the tiniest of these filters.  This is very particularly so on the one-petcock bikes.

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.

Fuel hoses:

Sometimes you can pull the hose off with your hands without excessive force, but often they really stick well.  The official BMW hose, whether the old silver braided stuff or the newer black metric gas line, is slightly less in OUTSIDE diameter than American fuel line...and, being smaller, fits the cross area of the airbox. All fuel hose of any type, but especially rubber types, tend to 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 strong pull. That tends to tighten the hose! it stretches the rubber, which is reinforced with fibers....just like the old Chinese finger-pull toy.  It also can crack or break the plastic outlets.    Better to use a very broad flat tool of some sort and push the hose at its end, whilst gently pulling on it. If replacing the hose, you can also cut it off.   I became anal about all this once and made a tool to remove hoses.  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 Chinese finger toy problem here. 

BMW does not use fuel line clamps on Airheads.

The best fuel hose I have ever tested is Tygon type F-4040A.

One that did NOT pass my tests (various solvents, gasoline components, ETC...short term and long term) is Masterflex "FDA Viton" 96412-D.  VITON of any sort is NOT recommended by me.

There is more on fuel hose at the bottom of article 12A


Perhaps once a year you should flush the bowl jets, pipe, etc., with something STRONG, like Berryman B-12 CARBURETOR AND CHOKE spray, using the wand, and replace the bowl gasket now and then.  When you do this, be sure to refill the carb with gasoline, as you do not want Berryman B-12 to be left in the passageways for long periods of time.  I re-spray the passageways with a mild cleaner.

Failure to empty the bowl can let 'stuff' 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 (on the CV carbs) won't work properly.  A bad bowl gasket, especially at the CV 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....!!!.  The upper-most part fits properly only one way.

GAS CAPS:   venting, various failures, locks and keys, ETC:  See article 1B

10/05/2003:  incorporate all previous changes & updates on the petcocks & cap removal methods
03/30/2004:  spelling typos, emphasis
03/31/2004:  Final version; add Fram filter number, minor clarifications, eliminate SOME redundancy
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
                    & much of the text was choppy.  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.
02/01/2010:  Add photos of gas cap drilling for venting, re-arrange article some, and add hyperlink
11/17/2010:  Add information on petcock straws
06/01/2011:  Clean up article, mostly for clarity reasons
06/04/2011:  Add /5 petcock sketch
04/03/2012:  Small updates, including adding Anton's article as a link
04/04/2012:  Clarify and emphasize details on cap drilling types and methods and why/what
07/21/2012:  Add a bit of information on my testing of fuel hoses, and my recommendation of
                    Tygon F-4040A
08/28/2012:  Add to the petcock overhaul section.  Add QR code.  Change Google ad & meta coding.
11/14/2012:  Totally revise, clarify, eliminate duplications, expand some areas.
12/01/2012:   Add DIRECT link to Vetch's article
04/15/2013:   Add part numbers and information on screw cap trim ring and gasket.
08/26/2013:  Add info from Tom on drilling SHED cap
08/06/2014:  Add information from BMW bulletin on the cap drilling.
09/02/2014:  Remove seat-tanks fitments to another article; remove fuel hose info (see 12A).
12/10/2014:  Combine statement from mod4performance, edit, and include, with the petcock flow info.
07/15/2015:  Clean up article some, eliminate SOME redundancies, clarify a few details.

Copyright, 2014, R. Fleischer

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