OILING
SYSTEM, BREATHER, AND RELATED ITEMS
©
oilingsystem.htm
50
Everything that
follows here is my personal belief, and a NON-leaking engine is
assumed.
OIL USAGE:
In my opinion a good running airhead....particularly the later
types with Nikasil....or earlier iron barrel ones in good
condition...will have over 3000 average-joe-rider miles per
quart. Over 5000 is NOT unusual. With the Nikasil
cylinders, this can often be the situation for over 100,000
miles, even as valve guides wear out. Some
riders like to go above 6000 rpm (roughly) a LOT. They will
use oil up much faster. Riders in super-hot desert
type weather conditions will generally use oil faster. Oil
usage goes up as valve guides and rings (also old iron cylinders)
wear. I want to caution that the quality of the oil has a
LOT to do with oil burning, and perhaps even a bit moreso if one
has the early low capacity oil pan, especially on the larger
engines. The condition of the breather valve
and if the stock breather hoses are in place, may also affect
things a fair amount too. I actually worked on a
breather setup once in which the hose arrangement by the owner
had such a nice slip-stream effect that it literally tried to
suck oil out of the engine breather. Cheap oils almost
always have additive parts of the oil compounding that burn off
rapidly, and that is NOT a great idea....because sometimes it is
some valuable parts of the oil that disappear too fast.
Some fairly good changes in oil viscosity can occur, and there
are cheap wear protectants in most car oils which are NOT
designed for air cooled engines. As the engine burns oil,
it tends to leave some deposits, coking/carbon, on the top of the
piston, in the upper ring grooves where the temperature is hotter
than below, and on the head. That raises compression
ratio, but also leaves nice places for some of that carbon to
glow red, and cause improper ignition. Use of poor oils
can, due to the valve guides, tend to promote problems in the
guides, and deposits on the stems. There are other niceties
that happen, including a situation with the carbon absorbing some
fuel mixture....but that, and some other things, are mostly....as
I call it....Nerdie-philes information. Because of all the
variables, I hesitate to give a maximum usage before any deep
investigation is recommended. Perhaps 2000 miles per quart
may be a point where some thinking should be done, and certainly
if maybe under 1000. If ring and barrel wear is the
cause, but compression is not too bad, and the valves are not
excessively old, I probably would just ride for awhile....but one
should not let wear go too far....penny wise, pound foolish.
Modern petroleum based oils (and, except for the temperature of
breakdown, synthetics too) are designed to work best in the range
of 110° C...130° C (230° F-266° F). Above 150° C
(302° F), oil breakdown increases exponentially,
and by about 160° C (320° F), degradation is quite
rapid. Petroleum oils will cease to
lubricate with any effect, at about 170° C (338° F)...synthetics
at about 190 C (374° F). For
practical purposes, petroleum oils are OK to about 240° F.
The temperature of the oil in the airhead oil pan is one
thing....it can be FAR higher in the cylinder head.
The thermostat, on models so equipped, seldom fails. They have been known, RARELY, to stick. This does not have any real effect on engine oil flow. The thermostat is NOT simply an on-off valve. The valve inside it determines what percentage of oil is routed to the cooler. The thermostat is specified to begin to open at 80°C (176°F) and be fully open at 110°C (230°F). GS models without the thermostat use a sized hole to control the temperature to the cooler, it seems adequate, although using a lot of rpm with the engine oil itself, at startup, being at very low temperatures, MIGHT be hard on the cooler soldered/brazed seams. The GS cooler is also supposed to be COVERED in really cold weather, to avoid OVERcooling the oil.
For information in great detail about the oil
filter canister, oil cooler system, etc., refer to this website
elsewhere's, especially OIL.HTM;
and, also the Technical Tips section at the Airheads Beemer Club
website:
http://www.airheads.org
Note: a sketch, with
notes, on the oiling system passageways, etc., is at:
oilsketch.htm
Those notes contain information on many things
dealing with the oiling system...and some changes made by BMW.
The BMW airhead uses a wet sump oiling system. That is, there is
a container, called the sump, which you might call the oil pan,
that holds most of the oil, and plumbing/piping is arranged so
that an oil pump draws oil from the sump to the oil pump for
pressurized delivery elsewhere's in the engine. The type of pump
design that BMW uses is called an "Eaton"...which uses
a sort-of trochoid arrangement. The pump is very long lived,
extremely powerful, and is capable of an enormous volume,
hundreds of gallons per hour at high rpm. It is best not to
remove the oil pump parts unless you have a reason to. I
do, however, remove the outer pump plate and take a few
measurements, and replace the oil seal, anytime the flywheel
(clutch carrier in later models) is removed. In the pump
area there is an index mark to line up and the vane has one inner
edge chamfered, which goes on first. You MUST replace the O-ring
if the plate is removed. I use a wee drop of Loctite BLUE
on each clean and dry screw and female thread.
Oil is lifted (sucked?) from the sump into the fixed non-movable
pickup, and that pickup, which dips well down into the sump, has
a coarse metal screen. There was a difference in the design of
the early pickup and the late one. The early model had a
small gasket on each side of an adapter that is on the top of the
oil screen unit; later models had the engine casting changed so
only one gasket is needed, and there is no adapter.
BMW has had at least three sizes of oil
pan. And....various oil pickups; dipsticks;....etc.
I have some of my own information in my Engine Internals article,
that is a bit different, particularly on the dipsticks. So,
see that article too. Instead of listing all
the variations of pans, pickups,... and putting photos here,
etc., Anton Largiader has done just about all of that already
(but, see my engine internals article for the rest), and here is
the hyperlink:
http://www.largiader.com/tech/oilpan/
In a rare instance of quite hot oil and
very abrupt braking, the system may loose pressure for a moment,
turning on the OIL lamp. Should you ever have your pan off,
that is a good time to gaze up and inspect a cam lobe, marvel at
the engine design robustness, understand what a tunnel-engine
means. At that time, clean the screen, and be sure no
cracks are seen in any part of the pickup and
casting!!...and that the two bolts are treated with a drop
each of Blue Loctite, and the bolts tight. If the spacer is
plastic, replace it with the later metal version. I use a very
thin amount of Permatex non-hardening
sealant on the pickup junction gasket(s). No sealant is needed,
and in fact NONE should be used for the pan gasket, and the pan
bolts must not be overly tightened,
which will warp the gasket and cause leaks. 5 or 6 foot
pounds plenty on the pan bolts. You can check them
after a few rides.
The oil pump is located at the rear of the engine, to the right
of the crankshaft, behind a 4 bolt (or screw) cover plate. The
center drive of the pump, which is the rear end of the camshaft,
is different on early and late models. That plate has an
O-ring, and if you should have your flywheel (called a clutch
carrier on the later models) out for such as a new main seal (and
flywheel O-ring on some models), then you should remove the
cover, install a new O-ring, oil it,
and immediately replace the cover
assembly. As noted above, I use blue Loctite on the clean
threads. Two types of O-rings have been used. The original was
black, and a later type which is a few thousandths of an inch
thicker, is red. Two types of plates
were used, one for taper head phillips screws, and one for bolts.
Allen bolts have also been used. The sort-of trochoid 4 lobed
vane is attached directly to the rear of your camshaft. That vane
rotates inside of a 5 lobe rotating ring, and it may be hard to
visualize how it works even if you have the cover off and are
looking at it....until the engine rotates, and all seems clear to
you (one hopes!).
The oil goes from the sump to the oil pump to the oil filter
canister, where the oil is presented to the OUTSIDE of the oil
filter, under very high pressure. The passageway (galley) from
the pump to the oil filter canister area is plugged at the left
side of the engine by allen plugs or screwdriver slot plugs,
and are best left alone. One such plug is quite
visible, the other is rearward and inward a bit (around the
corner, so to speak). That is, you will see one on your
engine below the oil pressure lamp switch...horizontal with the
left pushrod tubes. Another is a bit to the rear, 90° around the
corner, near where the transmission mates to the engine casting.
Very high oil pressure can be in this galley at engine start-up,
particularly if the oil is cold. The oil passes
through the oil filter element into the other engine oil galleys
(cast-in piping).
NOTE: The oil pressure switch is NOT at this part of the left side galley I mentioned above. Rather, that switch is located in a different part of the oiling system...MUCH farther down the line, actually in the galley that supplies the rear main bearing. The pressure in the switch area is about 14.5-29 psi at 800-1000 rpm; and about 60-74 psi at 4000 rpm. These are official figures, and will vary with oil temperature, type, and grade. That switch has threads of 12 x 1.5 mm. NOTE that very early airheads had a 3/8 NPT thread. ...also note that the later switch is the same as mid-seventies 2002 BMW car sender.
NOTE: The timing chain is oiled from the
output of the pressure relief valve, which opens around 75
psi. At very low rpm, the oiling is minimal. The
wear is not the chain, actually, but the upper sprocket, the one
on the crankshaft. It is common to call a sloppy chain
worn-out, but usually the sprocket is the worn part....but all
worn parts in that area are replaced normally when needed.
There is an article on this website on that...... timingchain.htm
***There have been a LOT of changes to the
oil filter area over the years. A considerable amount of
confusion has existed, and continues to arise. Do
not EVER guess at what you THINK should be fitted...see
the various Airmail and Airheads.org articles published, this
website at oil.htm, and remember that Haynes
and Clymer's, with all their sketches, are WRONG in some details
(BMW TOO!)!!! Do NOT
use a thick or even any outer gasket on the engine oil filter
cover on the models after the /6...those are any model NOT having
the INNER one-bolt filter cover. There are exceptions, read
that oil.htm article! The early
models with the inner cover are basically foolproof. DON'T
BE A FOOL, be SURE you TOTALLY understand how and what and why on
the later canister setup, whether you have an oil cooler or
not!!!
Be sure that there is a metal shim being used, against the canister edge, unless your canister HAS a lip..and even then it MIGHT be needed!!! Read that article!!! Failure to do things right can cause $$$$ damage. If the oil light ever comes on at IDLE, you MAY have done damage already!...except, perhaps, under severe braking. maybe.
There is that mentioned one bolt inner cover on
early models and there are several types of outer covers,
thermostat and non-thermostat covers, GS covers, metal canister
shim, two basic types of internal pipes, many changes in O-rings
and oil filter designs, use and non-use of a paper cover gasket,
ETC. Do something wrong here and you will soon have a much
reduced bank account. This is NOT the time to pose questions to
ME...do your homework if you have concerns. NOTE that
some BMW shops do NOT understand airheads!!!!.....do
NOT necessarily trust your BMW dealership mechanics to do a oil
filter change properly. You must KNOW that they have
considerable airhead experience!!!, and you can ASK about the
finer details...about those shims and O-rings! I suggest
you do it yourself.
The engine is lubricated by oil coming from the oil
filter/canister. If the filter is blocked, a bypass valve at the
inner wall of the canister will allow the engine to continue to
receive oil. In a VERY rare instance a collapsed and thus
failed oil filter has stopped oil from reaching the engine.
This may have been a poor aftermarket filter (??). It is MY
belief that the HINGED, BMW SOLD filters are the BEST, and
STRONGEST. The outlet for the canister is the
central pipe. In the non-cooler equipped bikes, the
oil flows from the outside of the filter into the short center
pipe, thence to the engine. In the cooler equipped models,
the center pipe is longer, and the pathway more convoluted, a
look at the outer flange cover will show you the
pathway.
From the oil filter canister, oil goes to the CAMSHAFT front
flange. There is a passageway here that is about 2.5 mm for
lubrication. Oil then travels upwards to the crankshaft front
main bearing area.
For an oiling sketch with NOTES!: oilsketch.htm
Things get complicated from that crankshaft main bearing area.
There are SEVERAL routes for the oil from the bearing holder
area:
1. There is an outlet that goes to the TOP two LEFT cylinder
studs.
The engine casting base area of each of those two TOP studs, has
a small hole. Oil travels from that hole outwards along the
cylinder studs to the valve gear, and on its return from the
cylinder head flows down the pushrod tubes to the sump,
lubricating the cam and lifter during its passage.
2. A similar pair of stud oil hole outlets lubricates the RIGHT
cylinder valve gear, and back to the sump in the same manner.
3. Another outlet goes to the oil pressure switch and the
crankshaft rear bearing. Pressure at the switch is likely to be
towards 30 psi at idle, and over twice that at high rpm.
4. Yet another outlet goes to the pressure relief valve, which
opens at about 75 psi. That oil relief valve is located in the
chain compartment at the front of the engine, it is a simple
spring loaded plunger. Since this point is WAY down
the oiling system from the pump...and oil has traveled through a
lot of smallish passageways, it is notable that the pressure at
the left side oil galley, the direct pump output, discussed
previously, can be very much higher, especially with cold
oil.
5. The crankshaft itself has a bore, and fed from the same area,
lubricating the rod big ends. Since the cylinders on a BMW
airhead are NOT directly opposite, these are separate.
6. The little ends (piston rod ends) are splash lubricated.
7. Oil from the valve rockers area flows back via the
pushrod tubes, and that lubricates the camshaft surfaces, etc.
All the oil eventually travels via bearing clearance flow and
valve gear flow, ETC., back to the oil sump, and the process
begins anew.
If your motorcycle has an oil cooler, some oil can be routed from
the oil filter canister area to that cooler. That system uses a
longer canister central tube and a special outer plate and
o-rings, etc., to ensure that oil can flow to the cooler. A
thermostat (or restrictive hole sizes) may be used in that outer
cover.
***NOTE: on models before the approximate 1981 introduction of
the electronic ignition models, oil routing was somewhat
different to the front bearing, but this is of no real
consequence. The exact serial numbers, dates, models, of the
changeover is not known by me...I think it was phased into
production so as to use up all the old parts/castings.
BREATHER/Breather
valve(s):
The crankcase breather is located in the starter
motor area, in two sections, to the starter's right. Oil and
moisture fumes are drawn into one or both carburetors and burned
during combustion. The early model breather looks like a round
disc with a small spring and a holding clip on the shaft. There
are two grooves in that shaft, the top groove is used for the
R50/5, R60/5, R60/6 and R75/6, and the bottom groove is for the
R75/5, R90/6 and R90S. This early type of breather valve has been
known to make honking noises (the later ones which are reed
valves can also make some noises, but usually they are quiet) and
can be removed and the later style installed. there is
nothing wrong with the operation and design of a good early disc
type breather valve. It is arguable if the later reed type
works better, but it IS quieter and does NOT seem to ever wear
out. You can make a new round disc from printed circuit
board green fiberglass material. NOTE that some of
these types of noises are often confused with noises in the rear
crankshaft SEAL (Turkey gobbler noises, honking noises).
The breather system appears to be simple, yet is more complex
than one might think, with settling chamber and using very faint
vacuum at the carburetor intake to allow it to function
properly. The breather system also has potential
problems. If the round disc is at all damaged, especially
if cracked or chipped at the edges, it will cause high oil
consumption. Just barely forward of
that disc is a small hole that was first introduced in the 1978
models, and this hole is often not seen with a quick
glance. It MUST be clear!! That hole allows condensed oil to
return to the crankcase. If the small
hole mentioned is not clear, oil consumption will be rather
high. DO poke a wire, or?, into that hole during inspecting
the breather. The actual system involves not just
this disc, or reed, valve area, but the outlet area forward and
to right of the starter motor. See oilsketch.htm,
in the textual notes, for more information.
UPDATING the breather
valve to the later reed type:
To update the valve you must remove all parts except the post, and then fashion a way to pry up the post, without leaving bits to fall into the tiny hole (assuming you have a 1978+). You can fashion a puller for the valve using socket and screw or?? The new valve consists of only three pieces, which include a membrane (reed) and a screw. Install so that the cap fits properly. Depending on the model, you may find the screw needs to point to the right foot peg, perhaps at about 5:00, tapping the assembly using an appropriate size of socket that clears the top reed stop plate. Use RED Loctite on the screw threads. Another way of saying this is that the open end of the reed faces the left handgrip....about a 10:00-11:00 positioning. Be sure your cap, etc., fits properly, and the reed is oriented correctly, before fully installing, as there are differences over the years in what the area and cap looks like.
If upgrading to the reed valve on a clam shell air cleaner housing model Airhead, you may want to upgrade the cap, using cap 11-15-1-335-756; hose 11-15-1-338-215; and gasket 11-15-1-338-431. The actual breather valve assembly is 11-11-1-335-712. The early R65 can use these too. These other parts are only really needed for these bikes of the clamshell variety (and earliest rectangular models???)....where the venting is directly to the airbox, with no intermediate junction.
***Be
sure to see oilsketch.htm
as it has a LOT more information on the breather
Starter cavity drain hole:
On the LEFT side of all Airhead engines, below the starter cavity, to the left of the dipstick, is a small HOLE. That hole is the drain for the starter cavity. If a breather hose fails, oil may come out of that hole.
In the 1985/1986 and later models a system of two electric solenoids, and a few other things, and a fuel tank modification, was standard on airheads shipped to the U.S. The purpose was several, one was to positively shut off the fuel, petcock or not, another was to route fumes from the fuel tank (perhaps the bike was in the sun, especially if parked?) into the crankcase, where the fumes would be sucked into the carburetors upon the engine starting. A vent pipe led into the crankcase, and that pipe was on the left side of the starter cavity (inside the cavity area). MANY folks have removed the solenoids, one or both, and may have removed the flapper valve in the fuel tank that prevented a full load of fuel. When that is done, venting to the tank is a must. The vertical pipe going into the crankcase MUST BE PLUGGED, because otherwise a LOT of oil CAN be dumped rearward into the clutch....and some will undoubtedly come out that left side HOLE.
Note: A RARE event, but has been seen now
and then, is an engine with the front main bearing having
rotated, which cuts off oil to the rocker arms, and lowers oil
pressure. You
will usually find a steel pin, of about 4 mm diameter, about 11
mm long, in the oil pan. Whilst
the main bearing is a press-fit, if the pin, which is supposed to
be pressed-in and staked, comes out (big oil pressure is there,
helping to push out the pin), then the bearing MIGHT
rotate. The pin is 11-11-1-253-184. This is a
SERIOUS event, and requires the entire front of the engine to be
disassembled.
As mentioned much earlier herein, oil capacity depends on model and pan fitted. Pan changes have been made for extra air volume for reduced breather output.
The Suburban
Machinery remote oil filter kit:
I am not in favor of
this product. See AIRMAIL, November 1997, for a
rather full discussion, pro and con.
For other oiling system things, such as information on pan gaskets,,,,ETC...see sub-section articles under Articles #60
Revisions:
04-18-2003: add .htm title; add oil deterioration
temperature information.
06-21-2003: clarify oiling system internal flow and
direction details; expand upon details of oiling system pressure
08-31-2003: add hyperlink to oilsketch.htm
09-06-2003: expand #4
09-21-2003: minor
09-26-2003: add top of page Oil Usage section
05-22-2004: Edit entire article for more clarity, minor
hints, more hyperlinks
08-24-2004: add oil switch threads information
10-10-2004: hyperlink re: breather
11-14-2004: add Suburban Machinery remote oil filter kit
notation.
07-05-2005: add slightly more information on breather oil
return hole, and re-arrange order of how I said it, slightly.
12-18-2006: add photo of late style breather valve
11-21-2007: Add Anton's website link on oil pans and
dipsticks
01-24-2008: Incorporate breather information from soon to
disappear engineinternals.htm
02-03-2008: Remove engineinternals.htm hyperlink
04-28-2008: add thermostat information