This page is about the BMW motorcycle models between 1955 and about the early
The Everbest petcock and its standard BMW tool to install/remove it.
The fuel filter is missing in this photograph.
The Everbest petcocks used on BMW motorcycles, were a bit odd to use.
They didn't follow the United States standard for valves and petcocks. The
text embossed in the castings are in German, not English. This petcock was
used from the first of the Earles fork models until the end of the /5 BMW series
in 1973. Both of the original tanks on the /2 BMW motorcycle used only one
petcock. All tanks on the /5, /6 and /7 had two petcocks. The reason
to use both is explained below.
The "off" position. See the "ZU" showing?
The "on" position with the "A" showing.
The "reserve" position with the "R" on the top of the
The Everbest petcock totally disassembled. This photo
shows black gaskets, not the typical red ones. Thanks to Brian Rozema for
This shows the crimp that must be "opened up" to get the barrel out and later
"recrimped" and you can see why it can be rebuilt a limited number of times.
This is the original hard red gasket used to seal the petcock to protect from
leaking fuel. If it leaks, see below.
The main and reserve tubes
You may find some variation from those figures. This is a NOS Everbest
fuel petcock from late 55 to the early 70's. See the bend in the main tank
stand tube? That is to have the opening of the tube at an angle. On the
small 4 1/2 gallon tank, the tube impinges upon bottom of the side tool box so
badly that the tube opening would get blocked. I have removed many
petcocks to find the brass tube mashed over to cover some part of the opening.
My solution was to cut a tiny bit off at an angle. That will result
in a slightly smaller reserve capacity, but allow full fuel flow during main
tank operation. This is critical on the R60/2,
as it was prone to piston seizure and this was
one factor described by BMW. I think that there was a service bulletin on
Do not cut the lower tube down to increase the amount of fuel on reserve.
That tube sticks up in the fuel a bit to try to stay above any water or dirt.
Everbest fuel filters
The petcocks come with a fuel filter built in. The filter is quite
good, but is delicate and needs very careful treatment. The very early
ones had a small mesh screen that was easily distorted. Handle with care.
The oldest style /2 filter in the Everbest petcock and what it looks like
when removed. Photos by Marc, thanks. I don't remember when they
changed the type of filter screen.
The later style screen fuel filter for the /5 BMW motorcycle.
Photo by Jeff Kuzmanoff, thanks.
That screen should be examined and cleaned every few thousand miles. Be
very careful with it as it is quite delicate. Get a new one for a spare as
you will use it eventually.
The Everbest was never a good petcock and usually leaked within a year or two
of purchase. The leak would be around the barrel and through the cork
gasket that was supposed to seal it up. I understand that it can be
rebuilt once, maybe twice, with some degree of success. I have never done
this and have heard of mixed results. Go to the well written article at
http://members.aol.com/vechbmw/petcock.html for more info. BMW finally
upgraded to the Karcoma petcock in 1974 for the /6 series. It is far
better and is often used for the older models too. It is a direct swap.
We always wondered how BMW could use such a poor item on a motorcycle for so
many years. At a service school put on by a factory instructor, I asked
that question. He laughed and told us that there is a "story" behind it.
Up to that time, (mid 50's) no decent system for breathing a gas tank had been
developed. A BMW engineer had invented a method for the tank to not need
venting at the gas cap. The fuel petcock would allow a lot of tiny bubbles
of air to go upwards in the fuel as it was flowing down. BMW patented it
and licensed it to Everbest. They were so proud of the invention that they
somehow have over looked the fact that in all other aspects of petcock
requirements, it was a failure. Even the previous petcocks on the early /3
were better for sealing gas.
Suggestion for /2 BMW motorcycle restorers
If you want to have an original petcock on your /2 restoration, I suggest
using a Karcoma for actual riding. For serious Concours D'Elegance judging
I suggest draining the tank and installing the Everbest. If the bike won't
be started up, then you won't need to worry about your old Everbest leaking,
especially if the tank is empty anyway. If you have located a good
Everbest, then it will soon leak if you add fuel.
The Karcoma petcock on the /6 BMW motorcycle
In 1974, when BMW came out with the /6 models, they also introduced a decent
petcock. It is made by a company named Karcoma and it works well. It
is easily rebuilt, but seldom needs it. Many owners are now forced to use
the Karcoma due to the lack of supply of the older "original" Everbest.
Later on, BMW used a Karcoma that had an angled fuel line connection and they
are harder to hook up with fuel line.
The three positions of a Karcoma petcock for BMW Motorcycles
This is the "off" position. It would also be "off" if
the arm was pointed to the left, as both positions are equal. This petcock
is the older type with the "straight down" connector.
This is the "on" position. This is the later petcock
with the angled connector.
This is the "reserve" position.
The Karcoma petcock for the /6 BMW motorcycles can be easily opened
up, but not so easily put back together again.
Once open, it can be cleaned up and that will usually fix any actual petcock
leak. Just remove the plastic cover and then unscrew the cover plate to
get it apart. Be very careful. Some use a bit of Vasoline on the
black rubber piece to allow tightening of the cover and still allow the hand
lever easy movement.
The Germa petcock was almost identical to the Karcoma, but the hand lever was
removable by removing the screw. Thanks to Steve D. for the photos.
Fuel leaks at the petcock threads
Upon installing a petcock you may find that it leaks at the threads.
Don't use teflon tape or any type of sealer on the threads. That is the
wrong way to do it. It is harder and probably won't work. It is easy
for one to think of the threads as in a plumbing connection. That would be
incorrect. The seal is at the reddish hard gasket (see above) that goes
between the petcock and the tank. Carefully inspect the matching metal
surfaces of the tank and top of the petcock for any type of defect. Sand
or file to make it a perfectly smooth surface. Use only a proper wrench to
tighten up that nut. That nut is quite special. It has right hand
threads on the top at the tank. It has left hand threads on the bottom
where it threads onto the petcock. It is similar to a turnbuckle in that
respect. Tightening up the nut will simultaneously pull the petcock and
tank together against the hard gasket. Hold the petcock in position and
start the threads at both ends at the same time. Then continue to hold the
petcock and tighten the nut. It must be fairly tight to seal. The
hard gasket can be reused, but check it for smoothness. All four surfaces
must be smooth and clean.
One or two petcocks?
Why you should use both petcocks on models that have two petcocks. It
is very important to use both petcocks for riding that requires a high fuel
flow. What is a high flow ride?
1. Running above 100 mph
2. Two up with a full fairing at 80 mph or so.
3. At 80 mph into a headwind of 20 and we are back into #1 above.
The R75 should run with both petcocks open.
When the tank is low and the load is high, you can get into trouble. I can
tell you that our race bike had this problem. It was light, with a small
rider and no wind so the load wasn't heavy. The state of engine tune was
medium. The petcocks weren't clogged. Normally it would go about 125
mph. One day before a race, with both petcocks on and the tank low, but
not on reserve yet, it wouldn't go above 115 mph. Adding fuel solved this
problem. This translates to a very marginal fuel delivery system for a
stock bike with sizable load at a high speed. In this case, the petcock
was operating as the main jet, not good.
Think about this when you have a serious load and adjust accordingly.
Don't assume that you have full fuel flow, unless you have measured it a few
minutes earlier. The stock filters can clog up very quickly. If you
put accessory filters in the line too, this is additional restriction. I
don't recommend them. That means LESS FLOW. I don't ever run on one
petcock at over 60 mph. Don't run low if you have a serious load on the
engine. Top ends have burned up by running out of gas. On the /2, it
was common for the piston to get so hot that it blew a hole in the top. We
call that a "holed piston" and the parts that blow down into the lower end can
get into the lower end and ruin the crank. The owner could replace the top
end and think all is well, but a few thousand miles later the lower end shows
symptoms of failure.
BMW motorcycle fuel flow tests
It is a good idea to measure the number of seconds that it takes to fill a
fixed volume container from each petcock. Record it for future comparison.
An Everbest will flow 100 cc of fuel in about 12-15 seconds with a half full
tank. Only when it would get up to around 20 seconds would I remove the
petcock to investigate it further. A full tank will flow more fuel than a
low one, so take that into account in your flow measurements.
Notice the appearance of normal flow, as you need to be able to recognize it.
Later when you have some high speed problem, you will be able to easily check to
see if it is fuel flow related. If you pull the fuel line off often and
let the fuel flow freely, you will eventually learn to see what is "normal" and
what is "too little".
If you think that you may be seeing less fuel flow than you want, here is a
quick test. Remove the lower end of the fuel line at the petcock that you
want to check. Use air pressure to try to blow any dirt upwards and back
into the fuel tank. Be sure to clean out both main and reserve positions.
Now test the flow again. If it has improved, then you have just proven
that the fuel flow system was clogged up. You haven't fixed anything at
all, only temporarily relieved it. This might get you home, but you must
drain and clean the entire fuel system soon.
Other /2 BMW motorcycle fuel flow problems
This crossover was almost completely clogged up. This
shows only some of the dirt.
The dirt that came out of a tank into a large dish pan.
This will kill a /2 top end.
The /2 BMW has a crossover line directly between the two sides of the tank.
The /5 BMW and later have this crossover below the petcocks. The later
system is far better. The /2 crossover tube can get clogged up partially
or completely. The connecting tubes for the crossover line are at the rear
and about the lowest place in the fuel. That tube collects the trash.
One can peer into the tank to check fuel level and happen to check the right
side. It will be fairly full, but the bike is actually out of gas, or the
top speed may be limited. This is because the left side is empty and the
crossover is clogged. This is very risky because by the time that you find
that top speed is limited, it may have already overheated the engine. It
is best to remove the crossover from time to time and make sure it is clean.
The crossover tube is far less likely to leak than the other two lines and
therefore it gets less attention. Replace it when you replace the other
fuel lines. Carry, as a spare part, a piece of the fuel line that is
pre-measured to replace the longest one that your model uses. It is easy
to shorten it if needed, but it is already correct for the longest one. It
also may serve as a test piece.
The /2 BMW motorcycle on reserve.
When on reserve, the fuel pressure from gravity is less. If the
crossover is clogged at all, then the left side will run out first. Now
you have another reason for a lower fuel flow: and that is that the fuel on the
right side must pass through a partially clogged up fuel line and then into the
petcock. You may have tested the fuel flow on reserve, but that doesn't
test the crossover line. Going on reserve should signal you that you may
need to reduce speed.
Aftermarket fuel filters
Finding the tank liner paint flaking off and getting caught in the filters
and possibly in the float needle valve can make one consider an inline fuel
filter. I suggest checking the fuel flow above the filter and below
it. I have measured many of these filters over the years and some
restrict as much as 50%. Don't use them. I recently
measured one that had about 90% flow and that is acceptable.
It has come to my attention that many modern fuel filters don't restrict fuel
flow by much at all. In that case, I too would use them.