Petcocks, fuel filters, fuel tanks,
fuel flow amounts, re-fueling,
clam-shell models choke lever operation,
fuel hose material, ETC.
© Copyright, 2014, R. Fleischer
PETCOCKS in general:
EACH petcock is fastened to the tank by both right and left hand threads. 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 on that petcock. 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 over the Airhead production years, 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; I don't bother. These discs have a locating tab.
They confuse some folks, so take notice of how they were assembled as you take things apart. You CAN figure it
out, if you forgot to take notice.
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, discs with holes in them. /5 bullet petcocks are not conventional in use.
In Petcocks with a Reserve function, conventional use is: pointing UPwards, towards the
tank = RESERVE. HORIZONTAL is OFF. German AUF DOES NOT MEAN OFF!
Early /5 Bullet Style Everbest Petcocks were different in how the handle indicated fuel flow, & the rotating handle
effecting gas flow from one or another port was in the opposite way from standard piping flow. Standard piping
flow indication by a valve lever is that the lever points to the tank or to the outlet, for flow. Here is a sketch of the
riginal slash-5 bullet petcock:
HINT! On these /5 bikes with the above petcock, the CHOKE cable tends to rub the underside
of the bullet area. That cable can 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. BUT THIS OFTEN CAN
BE DONE IF YOU GO ABOUT IT CORRECTLY. 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, if successful, you can retain the classic look of your /5.
These early bullet-style Everbest petcocks, as used on the /5 motorcycles, look like there is no easy way to
take them apart. If you can get them apart without destroying them, they ARE re-buildable. Frankly, while I
personally would not bother with the early bullet styles, Purists think differently and may well want the motorcycle
to be absolutely original in appearance, so trying to rebuild a bullet-style Everbest may be worth a try. You can
sometimes find brand-new bullet style Everbest petcocks on Ebay ($$$). Some have been able to force-twist
the /5 Everbest petcock apart for repairs. If that fails, you can do the UNcrimping.
You may want to read all the articles I link to.
NOTE: I have had problems with links to sites showing how to overhaul the Everbest. The links change, making them worthless.
I check all these links now and then. I thought it best in at least one instance, to copy and display Vech's information, below.
I copied the following from Buchanan's site, who had copied it from Vetch. The author, as noted, is Craig Vechorik, AKA
VECH. Craig Vechorik's website is http://benchmarkworks.com, where he has 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:
http://www.benchmarkworks.com/articles/howto/petcock.html If it works, you may want to read it, and then what I have
copied from Buchanan's site, below:
Rebuilding Everbest petcocks, Craig Vechorik
Everbest petcocks (used up to the /5) ARE rebuildable, I do it all the time. Buy a roll of 1/8 sheet cork at an auto parts store.
You must trim at the body a bit with a knife, to cut away a bit of the crimp they put in the edge of the hole that the plug of the
valve fits into. Then put the handle in a vise, and pull and twist the body, CAREFULLY, so you don't break the handle off, and
you will pull the plug of the valve, and the retaining washer ( which the crimp in the body holds) out. Clean out the body with a
round plumbers wire brush. Sand the plug LIGHTLY with 600 sandpaper. Then you cut out a piece from the cork sheet that
measures 1 29/32" x 1 1/6". Make sure that your cut piece is square and accurate. Grease up one side with wheel bearing
grease, and roll it into a more or less cylinder, and shove it, (with the open seam to the side of the body) into the body. Be
sure to get it all the way in, and square. Then grease up the plug and press it in. It will take a good bit of force, and I do it
with the aid of a vise. When you get it all the way in, take a small screwdriver, and a light hammer, and crimp the body just a
bit, to hold the retaining washer in. Then turn the petcock to the on position. (it will take a good deal of force at first, 'cause it
WILL be tight.) and find a drill bit that will fit down inside the brass supply tubes, and CAREFULLY drill the cork out of the
OPEN hole and the hole on the output side too. Blow out the crumbs of cork with compressed air, and turn the petcock to
the reserve position, and do it again. After you put it back in use, if you ever take it off, do not allow it to ever dry out. Put
the petcock in a jar of gasoline, with a tight lid.
............................................ .................................... ...................................
You have nothing much to lose if that method does not work, as you can always substitute a later petcock, so
here is another 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. See also link for rebuild parts. Most auto-parts stores have some cork.
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.
There is also an article on the various petcocks, including the Everbest, on Duane Ausherman's website:
Here is a link to a parts kit to rebuild the Everbest petcock:
Here is a link to a guy with an Ebay store. He can, I think, service yours; or, has cork gaskets, ETC:
The petcock service may not be listed, you will have to contact him.
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 using CORK inside for the active element can often be reclaimed to good operating
condition after being dry for years by simply soaking in very hot, even near boiling water.
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:
http://www.motobins.co.uk/bmw-parts.php?model=R Series 2 valve Twin
Have clean surfaces and a good grunt on that large outside nut....with equal threads being
engaged when fully tightened. This applies to all petcocks when installing them.
Most other petcocks have the screen inside the outlet, remove the outlet part to see and clean the screen.
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 enough that you SHOULD ADD an aftermarket filter between any petcock and the
carburetor. More later in this article.
TWO types of petcocks do not have an outlet screen filter, these have non-removable horizontal fuel Underneath the plastic cap you will probably find a sort of knurled edge that must be gripped in order My present method is to use two pieces of BRASS or ALUMINUM, which is soft, and works well with
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. There is a left hand side & 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. In mid-1980 & later, BMW added a tank fumes solenoid valve & a fuel flow solenoid
valve. These are located inside the cover that fits over the starter motor. There are holes in that
cover for hoses, etc. Because of this arrangement, BMW used 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 newer bonded filter screen. If you install all petcocks so
their OUTLETS pointing REARWARDS, then the curve of the fuel hose will be nicer, shorter, & the
hose might last longer. However, that requires one RIGHT type & one LEFT type.
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 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 disassemble, 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 washer...do this very sparingly. Silicone grease may be called
Dielectric Grease at your AutoParts store....and it has many uses on your motorcycle. The petcocks
will remain very easy to use for a very long time after you clean & FAINTLY lubricate them.
Except for the early /5 'bullet' style petcock, the other types of petcocks are easily taken apart.
Sometimes, on the LATER, non-Germa ones, it is a bit of fun to re-assemble.
HINT: one needs a good grunt to push the threaded nut & handle assembly 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, & pushing the petcock portion, ...SQUARELY!!...to 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, 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.
to unscrew 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 to show you a photo, but you CAN grip the edge in a vice & 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 & not mar the metal?
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, & 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 & how arranged. Which side fits the other side, where
& how the tabs fit, which disc goes back first, when re-asssembling.
Underneath the plastic cap you will probably find a sort of knurled edge that must be gripped in order
My present method is to use two pieces of BRASS or ALUMINUM, which is soft, and works well with
I usually find the rubber disc with the 4 holes simply in need of a cleaning (with the rest of the petcock Always service the fuel tank and petcocks by REMOVING the petcocks from the tank. You
too), & I reuse them, with a faint/light smear of common dielectric grease (a silicone grease) on the
rubber & all the moving parts. 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/feel to tell me! BUT...you CAN
reset the dimples 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 rubber disc, spring, and inside
the metal cap; all with silicone grease. If you do it all as I say, you may go MANY years before
having to repeat the cleaning/lubing.
NEED to see what grunge is there, thoroughly clean the tank, etc.
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 also 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 &
petcock threads being engaged.
Always service the fuel tank and petcocks by REMOVING the petcocks from the tank. You
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. 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, & when horizontal you
stop the fuel from flowing. HORIZONTAL IS OFF!
NOTE! Early bullet-style Everbest Petcocks do NOT work in this standardized way.
Aside note: Some Clymers books are WRONG on the position of the handle for the
choke (enrichener) ON CLAMSHELL AIR CLEANER MODELS. That means pre-1981.
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, water & other bad stuff 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 & you may get rust, and other nasties
into the petcock & 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 800 & 1000 cc models. If you have a hotted-up motor or 800 cc or 1000 cc
engine, hotted-up or not.... & a single petcock tank, you SHOULD enlarge the hole through the petcock
petcock, for additional flow at wide-open-throttle. Dot that to the straws too. Here is more information:
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 an R100 engine. Careful
drilling & modification of the petcock will work well. You CAN retain the in-tank thin tubes
leading upwards from the petcock, by drilling them out a SMALL AMOUNT. That is not easy
and you may wish to remove them, drill the petcock larger, all the way through, & fit larger
inside and outside diameter tubes to the petcock. I have had GOOD LUCK with carefully
reaming/drilling the existing stock straws!! A small change in inside diameter 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 even 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 in inside diameter makes for a rather large change in FLOW. THE most
restrictive item IS THE PETCOCK AND ITS FUEL STRAWS. If you carefully use a sharp and
LONG drill bit, you CAN enlarge the inside of the straws, right into the petcock, & this really
does work well. You need enlarge only a small amount. More on this, somewhat below.
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 and will work fine on all tanks. The straws can be metal or plastic. If yours are cracked,
you can usually use tiny diameter copper tubing available at hobby shops. If you need to,
sand the end area diameter of the metal tubing you purchased, and SLIGHTLY chamfer the
down side very end ...both for ease in assembly and proper fit. Consider using a SHORT straw
of 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. There is
NOTHING critical about the final length of the straws.
MORE on FUEL CAPACITY and FLOW:
For tank capacity, see your owners book. Understand that the USABLE amount of fuel is
LESS than the rated capacity. Few of you fill the fuel tank to the very brim, where no more
can be added. That is a BAD idea; the tank can be overly pressured from sitting in the sun.
Fuel capacity is not what is in the books & 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 AS IF you 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 TWO petcock tanks do NOT hold the same amount of fuel for main nor
reserve positions. 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 sustained high speeds I suggest BOTH petcocks be turned on, if two are available. This helps with
possible fuel flow including flow problems 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, & measure the real world situation, including restriction
effects of the float needles and seats, etc. The following test includes the flow through any external
aftermarket fuel filters AND the carburetor internal fuel valve, which is operated by the fuel level and
the float... so it is a good test:
For the very best results use TWO containers; do both carburetors at the same time. You CAN do
one at a time, but it is not quite as good, but still good enough.
Put quart containers, such as a glass measuring container from the kitchen, one under each carburetor,
& remove the carburetor bowls. Turn on both petcocks; see if you can get 8 ounces of fuel into each
container in 1 minutes or less. That is approximately the minimum required. Yes, a cup a minute, or,
nearly 1/4th liter. Most will measure one carburetor at a time. I suggest that you have a MINIMUM
of 8 ounces per minute per carburetor, both ON if you have two. 350 cc is OK. If you are
not getting that much, check filters.
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 if you run lengthy WOT or have a modified engine. The stock
single petcock will not flow enough fuel at extended W.O.T. Careful drilling & modification of the
petcock will work OK! It takes very little increase in the diameter of the petcock straws & petcock
passageways to rather greatly increase the fuel flow amount.
It is not uncommon to hear complaints of an Airhead acting like it is running out of fuel.....especially if
starting out from a well-filled tank, & you are at speed out on the highway. Usually this is a tank venting
problem or, a problem with the fuel cap. Especially on caps that say SHED on the bottom.
They can be modified easily.
If the tank is not cleaned regularly, perhaps yearly, especially if you don't fill up after every ride, or live in a
high humidity area, the tank may accumulate a fair amount of WATER, which
CLEAN THE TANK TOTALLY, at least yearly!!! Clean the filters at the petcocks regularly; replace
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, with soap, on the tank insides, then
wash the tank & 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. NOTE that 100% filling to the brim is
NOT generally a good idea....due to pressure effects from temperature changes, particularly
if the tank is in the sun. Think about your usage, and your filling.
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. This also applies to finer screens, which do only very slightly more cleaning.
The Napa 7-02323 & FRAM G4164 are similar, although not so in quality, & 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 1/4" bump. I recommend against this item & its size unless you have to use it, or
have a very much 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; more often filters do NOT have
markings for flow direction. 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.
Napa, and seewww.napaonline.com, has changed its numbering system slightly.
All these filters work best VERTICALLY, but are OK horizontally, but have less hose & vibration strain
on the plastic if used vertically. DO NOT fail to replace these filters now & then & do NOT fail to
clean the tank regularly & clean the petcock filters now & then. If your tank is fairly clean inside,
you may get 20K or more miles on aftermarket filters before they need replacement or cleaned, if
that is possible on your types. The clear plastic ones, depending on make & model, sometimes
can visually show you if they are getting clogged, by looking at the paper pleats & sediment. DO
NOT DEPEND ON THAT.
Aftermarket external filters are a big help because it takes hardly anything as thick as a human
hair in the carburetor to cause problems.
Note that if fuel flow decreases enough, your engine will run lean & potentially hot, might stumble some, & 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; and advise modifying the petcock on single petcock tanks, if used with over 650
The best fuel hose I have ever tested is Tygon type F-4040A.
Tests were run for YEARS on the same
pieces of hose, for flexibility, changes over miles/time, etc.
One that did NOT pass my tests (various solvents, gasoline components, ETC...short term and long There is more on fuel hose at the bottom of article 12A
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, don't leave Berryman B-12 in the passageways for long periods of time. I re-spray
the passageways with a mild cleaner, even brake cleaner is OK.
GAS CAPS: venting, various failures, locks and keys, ETC: See article 1B
© Copyright, 2014, R. Fleischer
Return to Technical Articles LIST Page
Return to HomePage