BMW Motorcycles are pretty reliable, but they do need
maintenance - it's no good buying an old (or not so old!) BMW and expecting it
to perform flawlessly, year in and year out, after receiving nothing more than
the lowest level of maintenance. Many of the necessary tasks are not included
in any manual, and some of the most annoying traits, such as dripping
carburettors, seem to have been accepted as being all part of BMW folklore.
There is no good reason to accept these regular problems, as there are few
tasks which require great skill, particular knowledge, or special tools, and
what is necessary can often be improvised or hired from the BMW Owners
SAFETY IS PARAMOUNT!
Always remember that working on your motorcycle can be fraught with danger the
risks range from having it fall over on top of you, to setting it and your
house on fire, not to mention the possible consequences of poor work, which
could result in an accident at speed! Decide what is involved, and obtain any
necessary spares before you begin work. Always keep the machine well secured,
use the correct tools, keep the workplace clean and tidy, keep children away,
check your work carefully, and if you have any doubts, ask someone who knows
your life, and those of others, could be at risk. If in doubt, don't do it!
Oil Filter Replacement can wreck your
engine, if the steel shim and '0' ring of post-'76 models are not fitted
correctly! Always fit the shim into the crankcase, then place a new paper
gasket onto the cover, followed by a new '0' ring. Modern filters have built-in
seals on their ends, in lieu of the small '0' rings previously fitted. Remember that many of the '0' rings used on Boxers are of fluroelastomer
material, and if overheated will produce hydroflouric acid this very unpleasant
substance will pass through your skin, and progressively rot your flesh. Always
handle any decomposed rings (eg: from a fire-damaged motorcycle) with caution,
using rubber gloves and tweezers. Wash the area with plenty of water before
handling. If you are contaminated, wash thoroughly, and seek medical treatment
immediately! Remember f left too long before treatment, amputation may be the
A Slow Boxer
is often one which has recently received new float needles, and has had its
floats adjusted by the original method this latest method works for all Boxers.
With the carburettor on the machine, and the float fully lifted, turn on the
fuel. Slowly lower the float, until fuel just begins to flow - the metal float
bridge, and the molded line on the float, should be parallel with the float
chamber joint face. At this point ensure that the operating tab is at 90' to
the needle. This may require re-alignment and if so, the above procedure will
need to be repeated.
Does Your K-Series Battery Charge warning lamp glow slightly, particularly when
the heated grips are turned on, becoming brighter with engine speed? Don't
worry this is a characteristic of all K-Series models, and is due to the sum of
the voltage drops across the large number of connections between the battery
and warning lamp, one of which also supplies the heated grips. Without running
another wire directly from the battery to the warning lamp, there is nothing
which can be done about it, but at least you know the warning lamp is working!
Can't Start Your
K-Series? Power for both the starter push and the clutch switch comes
from the same source fuse no.1 (instruments) which can blow due to a faulty
heated grip. Later 16-valve and 1100 cc models also use a sidestand switch,
which is not above suspicion.
Don't Leave Your K-Series idling while you don your
helmet, or have a last cigarette at idling speeds the mixture strength is
dependant solely on temperature, and can be very rich on a cold winter's
morning. Just start up and ride away!
Does Your K-Series Oil Level Rise? Strange as it
sounds, a faulty fuel pressure regulator can pass petrol directly into the rear
throttle body in sufficient quantity to pass the piston rings and enter the
sump! This only takes place at high vacuum levels, and cannot be seen at idle
Older Boxers are fitted
with resilient mounts for their rectifiers (diode boards) which can fail,
short-circuiting the battery cable against the inside of the front engine
cover. This can be both exciting and expensive, so check regularly and change
these mounts every few years.
The Alternator Excites through the battery
charge warning lamp, and if this circuit is broken by a faulty bulb, the
alternator will not self-excite until about 5,000 rpm. Always check that the
alternator warning light is on when you first switch on. It should be
completely extinguished by 2000rpm.
Low Alternator Voltage can often be traced to an
inaccurate voltmeter - always have yours checked against a known good meter
before starting to worry about the various expensive possibilities!
Battery Charge Warning Lamps which
do not go out can cause some worrying, but always remember that if you reduce
the load to ignition only, the battery will run the engine for most of the day.
Carry some lightweight jump leads, which will enable you to recharge from a
friend's machine, and most of your immediate problems will recede if you have a
faulty charging system.
Trafficator Switches operate by connecting to earth, so if your
trafficators will not operate, check that the 'Cancel' switch is not earthing,
or if one side operates continuously, check that its switch is not earthed. The
easy way is to unplug the appropriate switchgear cluster, before checking
further with a test meter.
'Soldered' Joints within a Boxer wiring harness are actually crimped,
and it has been found that after about ten years, particularly on the R45/65,
water has collected inside the outer sheath and corroded the crimps. The
resultant copper-based slurry will conduct, but at higher currents the voltage
drop can be enough to cause strange problems, such as total power loss, with
the engine stopping, when main beam is selected. Should this occur at night it
could be very interesting!
Fail Regularly on pre-1984 Boxers are not fitted with fork gaiters. The
fitting of these useful items is easy enough. You need 2 gaiters and 4 clips.
If so protected, your fork seals will last almost indefinitely.
Petrol Cap Jammed? This is not
uncommon on older Boxers, the cap spinning round but not unscrewing! It can be
removed without damage to paintwork by standing on the footrests, and passing a
rope through the filler cap handle; tie it into a loop around your shoulders,
and heave - the whole cap will pop out easily.
K-Series Valve Clearances do not need
adjusting very often - check them about every 30,000 miles or so, and remember
that removal of the cambox cover deprives the cams of the oil baths in which
they normally rotate. Coat each cam with grease before replacing the cover,
using new seals in all positions.
K100 Silencer Stuck? Apply some heat from a blowtorch
(having first removed the petrol tank), and then allow some engine oil to soak
in for a while. Repeat the procedure, and twist the rear of the silencer,
pulling to release the silencer from the pipes. Apply Optimol TA anti-sieze
grease before replacing. Replace the clamps in their original positions, and
remember to fit the tongues of the clamps into the cut-outs in the silencer
stubs before replacement.
and the Twins post '81 Swinging Arm Bearings may be 'sealed for life',
but they can be unsealed and greased easily. Using a pointed scriber, open the
bearings by attacking the outer seal from its inner edge, and the inner seal
from its outer edge, after which fresh grease can be worked through the
bearing, and the seals replaced.
K-Series Fixed Swinging Arm Pivots are usually very
tight, and many are damaged during extraction. Carefully use a small blowtorch
to warm the gearbox casing around the pivot (having first removed the petrol
tank), and lever it out with small tyre levers (BMW ones are ideal). The cause
of this problem is usually corrosion on the pivot pin. Remove the corrosion
with emery tape before greasing and replacement.
Radiator Fans can become stiff through lack of use,
so after winter lay-ups always turn the fan by hand before starting the engine.
A seized fan can be the cause of a very expensive overhaul I!
Older K100's Seem to Get Very Hot
before their fans cut in, due to different engine thermostat settings, so if
you have doubts, check with a good thermometer before buying new sensors etc.
The fan should cut in at 103'C, before the warning lamp operates at 111'C.
Starting a K-Series with a flat
battery can not only cause the ABS unit to register a power supply
problem, but can also cause more severe problems - as the starter contactor
coil will operate at reduced power, its contacts will not be held together
tightly, and arcing will result. In extreme cases, the contacts can become
welded together, making the starter motor run continuously - it's cheaper to
buy a BMW power socket, through which you can keep the battery fully charged.
Battery Charging via
the BMW power socket is recommended by the manufacturer, subject to a limit of
4 amps. Remember that batteries give off Hydrogen while on charge - do not
smoke, or use naked lights in their vicinity!
A BMW Voltmeter left in situ can make a good
diagnostic tool, if it is connected via a small jack socket; insertion of a
test lead will then reconnect the meter to the test lead, and you can check all
manner of circuits with it, except the alternating current output of the
alternator at the red, yellow, and blue wires. If you are going on a long run,
carry a small multimeter.
Voltage Regulators can fail, but are easy to check - just unplug the
unit, and connect the blue and black wires of the plug together while the
engine is running. If the alternator voltage increases sharply, the voltage
regulator was faulty. On the older electromechanical type, the internal
contacts are sometimes the culprit, and can be cleaned, but the solid state
units must be replaced.
If Your Battery Fails to Charge, always
ensure that the alternator brushes are making good contact with the sliprings,
that their holder is clean, and 12 volts can be measured at the brush connected
to the black wire. Should this not be so, the voltage regulator or connecting
wiring should be examined. If 12 volts is present, lift the 'brown' brush with
a piece of cardboard, and measure for 12 volts at its slipring - if this not is
present, the rotor windings will be faulty. Remove the cardboard, and measure
at the 'brown' brush - if this does not read zero volts, its earthing is
faulty. If these tests are in order, use a multimeter to measure the AC output
of the alternator at the red, yellow, and blue wires - if 12 to 14 volts AC is
measured here, but the battery voltage does not rise at higher engine speeds,
the rectifier (diode pack) is at fault, and must be replaced.
When Replacing a Diode Board,
remember that the black wire should be connected to the starter motor solenoid.
Many owners connect this to the most obvious place - the spare terminal at D+
on the back of the Diode Board! In such a case no harm will have been done, but
the starter motor will not operate. Both terminals on D+ are connected to the
same place, and either can be used to connect the blue wire. Remember also that
the earth cable must be connected from the negative heat sink - off one of the
upper securing bolts - to a clean area of aluminium, thinly coated with
Injection system, as used on the K75 and K100, is probably the most
reliable piece of the machine, and many apparent problems can be traced to low
fuel pressure. Should your K splutter to a halt, always open the filler cap,
and turn the ignition on to check that the fuel pump is running - if not, check
the fuel tank connector behind the RH side panel, and then the fuel pump relay
in the housing below the tank, and its fuse. Other possible causes of fuel
starvation are the pump pick-up filter screen (Remove the pump to see it) and
the fuel filter - if you have had any water in the tank, it may be choked, as
it will not circulate water. Remove the filter, and join the pipes together
until you can obtain a new filter. (Ideally, always carry one!)
A K-Series Which Will Not Exceed 50
mph or so is not fun, and the answer could be that the throttle switch
is jammed, so telling the injection unit that the throttle is closed; in this
case, it will shut off the fuel supply above engine speeds of about 3,000 rpm.
What Should You Take on a
European, or other long tour? The means to stay mobile is paramount - a
BMW pump, tubed and tubeless tyre repair kits (with tyre levers), followed by
inner tubes (even if you have tubeless tyres), and a small tin of instant tyre
repair. On the electrical side, lightweight jump leads, plug leads, spare bulbs
(mandatory in most countries) and fuses, are a good start. Always take some
stiff wire, nuts and bolts, and nylon cable ties, and PVC tape. Most European
states require a first-aid kit, with rubber gloves for use in Aids-concious
Germany. The level of spare parts is up to you, but a fuel filter (for K-
Series) clutch and throttle cables, spark plugs, and contact breaker points (if
required) is a good basic level. Remember that engine oil is very expensive in
Europe. Some people carry spare coils, voltage regulators, alternators, etc!
Whatever you take, know how to use them! The best insurance to take is a
reliable motorcycle and a Moto-Bins catalogue. Remember we are always ready to
despatch parts anywhere in the world. We can arrange very fast overseas
delivery often within a day or two.
Stow Your Pump on Monolever models inside the top frame
tube but always slide it in with the valve end first (handle last) and secure a
piece of string or wire around the valve end for easy removal. Make sure the
pump works well, oil its spindle, and, on twin-shock models, seal the handle to
the pump body to prevent the ingress of water and grit from the rear wheel.
Float Needles should be replaced every ten years or so, as their
rubber tips eventually harden, resulting in that well-known 'dripping
Needle Jets become worn as the needles vibrate within
them, so passing extra fuel, and increasing your fuel consumption. The needles
also wear, particularly the later brass types if in doubt, change them. The
replacement interval varies with the average engine speed, being about 15,000
miles for the lower-geared models such as the R45/65, to 35,000 miles on the
lazier large-capacity types such as the R100 series.
Cold Starting Problems can often be
cured by replacing your old float chamber gaskets unless they provide a really
air-tight seal around the choke fuel pick-up tube, the fuel level in the
auxiliary chamber will not be raised, and the cold start mixture will not be
further enriched during initial operation. The Auxiliary Carburettor itself can
often become loose, so being by-passed and ineffective; the resultant air leak
will also promote 'surging' at about 40 mph on a small throttle opening change
the gasket every few years, and make sure the screws are really tight.
Wheel Bearings are probably the most
neglected part of any motorcycle, and on the older, twin-shock Boxers the
near-side bearing in the rear wheel can totally fail with little warning. Its
seal becomes worn by exposure to grit, allowing road grit and water to
contaminate the grease. The off-side bearing is well protected within the hub,
and like the front wheel bearings, gives little trouble. Always remove the
inner races of your bearings every year or so, washing out all the old grease,
and re-packing before replacement with new seals. If you ride throughout the
winter, re-grease the near-side rear bearing in Autumn and Spring. Remember -
new seals are cheaper than bearings! The front wheel bearings of the later
Monolever Boxers and K-Series models give little trouble, even after extreme
Steering Head Races on R45/65,
R80ST models can often suffer premature failures, their outer races
showing regular dark lines where their rollers have made contact. These lines
are the sign of electrical erosion, probably due to tracking across the
tachometer's ignition coil connection on the printed circuit board to the steel
case of the instrument. Make sure that you earth the upper fork yoke to the
main frame earth below the fuel tank, to provide an alternative path.
Alternator Brushes leave a
conductive residue across their holder, so gradually diverting current from the
rotor. At the end of every summer, clean the holder by pushing a piece of card
below the brushes, and sliding it across the base of the holder until clean.
Brushes usually last for about 20,000 miles on smaller models, and 40,000 on
the larger types.
Alternator Trouble. Your friendly RAC man
may be able to obtain a new rotor for you, but he will not have the extractor
bolt required to remove the old one - they are cheap, and easy to carry, so
don't go on a long trip without one!
Does your old Boxer feel like an old dog? Fear not
- it may just be asking for some attention to the preload settings of its
wheel, swinging arm, and steering head bearings. A day spent setting up these
bearings is a day well spent!
Rear Crankshaft Seals are easy enough to change,
but it is also easy to damage your internal crankshaft thrust bearing in the
process. Before attacking the flywheel bolts, always locate the crankshaft
fully backwards. This will prevent the crankshaft from being forced forwards
when the seal is levered out, or the flywheel is replaced. Remember - a damaged
thrust bearing will require a full engine strip to replace! On post-'81
Models, remove the crankshaft end cap by levering under the groove around the
centre boss - use small tyre levers supported over the cap. Remember to replace
the '0' ring inside the cap, or inside the flywheel on pre-'81 engines. Before
fitting the latest-type seal (the type without a spring-loaded lip) always soak
it in thin oil for 2 hours, and carefully work it to form a tube which will fit
over the nose of the flywheel or crankshaft end cap, as appropriate.
Rear Wheel Drive Splines on
twin-shock Boxers can sometimes resemble ratchet teeth! Don't let this
expensive malady happen to yours - clean and lubricate them regularly with LM
47 Spline Lubricant, and recoat lightly every time the wheel is removed.
A Worthwhile Winter Job is to
remove your gearbox to clean and lubricate the clutch splines and pushrod -
with OPTIMOL T WHITE PASTE.
Pre-Paralever K-Series machines can often
suffer from an accumulation of water inside the swinging arm, which usually
enters via the joint face between the final drive and swinging arm. This water
will eventually contaminate the grease on the splines of the drive shaft, which
can result in a very expensive failure of the drive shaft, and sometimes also
the final drive pinion shaft. Remove the final drive every year, pull the drive
shaft out, and recoat the splines with Optimol T White Paste. When replacing
the final drive, coat the joint faces with a non-setting jointing compound such
as Blue Hylomar.
K-Series owners should also grease their drive shaft splines at least
every 20,000 miles with Optimol T White Paste.
R100GS Owners should also check their drive shafts
regularly - every 10,000 miles remove the front gaiter to check the drive shaft
coupling, and slowly rotate the rear wheel to inspect all the needle rollers of
the coupling for wear. They have worn through the coupling yoke before the
owner is aware of a problem! Remove the rear gaiter, and check the other
coupling, then work a little Optimol PL White Paste into the splines, and
bounce the suspension to draw it in.
K-Series Clutch Release Arms pivot on a pair
of needle rollers, which are usually attacked by water thrown off the rear
wheel. Replacement is easy enough, but prevention is better - drill and tap a
hole for a grease nipple in the flat area behind the pivot, and cross- drill a
2mm hole from its base to pick up the pivot bore between the bearings.
Stainless Steel exhaust pipes turned
brown? They can easily be cleaned by use of Wonder Wheels wheel
cleaner, followed by Solvol Autosol.
Batteries will generally last for years, if
taken care of. Fit a BMW-type power socket, and connect a constant-voltage
battery charger when the bike is not in use. Remember that the resilient mounts
under the battery carrier also deteriorate, and replace them every 6 to 8
years. The golden rule is never to leave your BMW with a flat battery. If you
let this happen, the plates will irresversibly sulphate. This applies equally
to new or old batteries alike.
Exhaust Valves have a definite life, after which they
are liable to lose their heads, with terminally expensive consequences for the
piston and cylinder head! The R45/65 valves, with their 7mm stems, can fail
after 35,000 miles, while the 8mm stem valves fitted to the larger models
should last for 50 to 60,000 miles. Prevention is cheaper than cure!
Exhaust Port Nuts on all Boxers
should be removed and all threads coated with fresh Optimol TA anti-seize
grease every year. With a cold engine, slowly pour a kettle of boiling water
over each nut before removal. If this fails, drill a row of 2mm holes along the
nut, and split it off with a chisel - new nuts cost a lot less than reclaiming
a damaged thread! Tighten fully.
Cylinder Base Oil Leaks on Boxers often come
from the pushrod tube grommets - use of the special tool, which can easily be
manufactured, and a sharp tap with a two-pound hammer will usually effect a
Petrol Taps require
lubrication too! It's amazing how easily they operate after being stripped,
cleaned, and their indexing plates greased.
Neutral Switches are easy to change, in spite of
their location, although many 'professionals' have charged customers for
gearbox and swinging arm removal! Just support the back of the engine, remove
the rear mounting stud, and knock out the long aluminium spacer. Remember that
the /6 and /7 Series switches are different, and don't forget to drain the oil
BMW HT Leads are of
excellent quality but no HT lead last forever. On the Twins they are exposed to
extremes of temperature as well as all that the elements can throw at them. If
tracking from the HT terminal to the steel shroud takes place, massive power
losses can occur, particularly at large throttle openings. Remove and clean
them regularly. If tracking cannot be cured, replacement is necessary life. We
recommend replacment of the twins HT leads every 5 years.
One of the Few unreliable
parts on a BMW is the early type of double-ended ignition coil found on
the post-1981 R45/65, R80GS, and all Boxers from 1984 to 1992. These coils -
usually with grey cases and Bosch part no 0.221.500.200 will let you down
sooner or later! The usual symptoms are ignition failure in wet weather, poor
cold starting, and intermittent failure. Check the plastic case for signs of
cracking, and be ready to buy a new-type coil, particularly if a long trip is
to be undertaken. Better still, buy a new one now! New type coils have Bosch
Failures of the Bosch electronic ignition system are rare, but
intermittent failure can be caused by overheating. The unit is seated onto its
heat sink with a thin coat of white heat transfer paste, which gradually dries
out. Remove the unit every ten years or so, clean both surfaces, and apply a
thin coat of paste, which is available from most electronics suppliers.
Early (pre-1981) R45 and R65 models
can fracture their front coil bracket - as this carries the main earth
connections a total electrical failure will follow, which can be dangerous at
night! Fit an extra earth cable between the coil bracket earths and the main
Gearbox Oil Going White?
Emulsified oil is a symptom of water being absorbed, and in the case
of Boxer gearboxes it usually enters along the outside of the speedo cable. Fit
a new boot and grease the cable/gearbox contact points and your troubles will
Big Ends' Gone?
It's probably only a noisy timing chain, particularly on post-1979
models with a single-row chain. The chain will become noisy after 30,000 miles,
but the original tensioner blade does not provide any tensioning after initial
wear takes place. Fit the latest, all-plastic type, and live in peace with your
Boxer! At high mileages this is also a good opportunity to replace the spring
in the oil pressure relief valve, and check that its piston is seating
Get the Dip Stick in? On pre-1979 Boxers the oil pump pick-up strainer
can split at a spot weld, and a vibration-induced crack can spread across a
securing bolt hole. The strainer can then become loose, and pivot across the
dip stick entrance. It can also cover the pick-up hole, so don't delay your
When Removing a
Clutch Plate, it is a good time to carefully fill the ignition timing
marks with white paint, to improve their visibility. In the interests of
personal safety, always use the correct tools to decompress pre-'81 Boxer
clutch spring. On post-'81 Boxers and K- Series models, progressively unscrew
the 7mm socket screws in a diagonal pattern. Be prepared to replace them, and
always change their shafeproof washers.
When Replacing a Boxer Timing Chain, mark the
sprockets with paint, as the timing mark on the crankshaft sprocket is hidden
by the outrigging bearing.
Gearbox Bearings are a very tight fit on
their shafts, so when fitting replacements, heat them to 200'C. When removing
layshaft bearings, which are very close to the adjacent gearwheels, start them
on their way by carefully levering with small tyre levers - the BMW type are
ideal. Pull off the large bearing at the front of the output shaft by engaging
the legs of the puller below the adjacent fifth gear wheel. Heating the Gearbox
End Cover makes it easier to replace.
Intermittent Loss of Fifth Gear is not unknown,
and is usually due to the cage of the front output shaft bearing having broken
up, allowing the balls to crowd to one side, and the shaft to move outwards
under load. Continued riding in the lower gears is possible, but can promote
Loss of Gear
Selection is caused by fracture of the small spring which holds the
positive stop link up against the camplate pins. It is possible to invert the
entire machine, in order to select third gear, and ride home with that...
really - it has been done!
Out of Gear can be a symptom of the camplate indexing roller having
broken up, or its spring having broken - a gearbox strip is the only answer to
Covers on post-'78 Boxers are usually difficult to locate on the pin at
the bottom - drill out the hole in the cover to be a free fit, and remember to
grease the pin. Before removing or replacing the cover, disconnect the battery
to prevent a short from the positive side of the Diode Plate.
Silencer Mounting Bolts on
twin-shock Boxers usually strip their threads after about ten years - it is
possible to tap their captive nuts to M8, but more reliable to fit longer
stainless steel bolts with nylon nuts behind the brackets.
ATE Front Brake Adjustment on pre-'81
Boxers can be difficult - make sure that the caliper pivot spindles rotate
freely in their bushes, and in the calipers. After adjustment, don't forget to
check the adjustment of the master cylinder operating arm.
R100RS and S Models with a Brembo
rear disc can present a struggle when it comes to wheel removal, if the caliper
bracket is seized onto the spindle - remember to grease the bush in it's
centre, or even fit a grease nipple. Likewise, remember to remove and grease
the bolts on the torque stay, so that you can undo them by the roadside.
Pre-'81 Boxer Centre Stands
can give trouble, mainly due to their pivot bolts becoming loose, wearing the
threads in the frame lugs, and twisting them. In most cases such damage can
only be repaired by welding and re-threading, or drilling out and manufacturing
stepped pivot bushes, neither of which is easy with the engine in position.
Make sure that your bolts are tight, and the stand is well-lubricated.
All tubular BMW Centre Stands
eventually suffer from wear and rust, particularly the K-Series - an internal
application of anti-rust wax will prevent corrosion, and wear at the contact
spot can be stopped by avoiding 'riding' the bike of its stand while carrying
your weight particularly against the front brake. If badly damaged from either
source, a new stand is the only real answer. The single skinned K-series stand
can also suffer from weld penetration and exterior corrosion, so check yours
now. Consider replacing with the later K Centre Stand from the 16 Valve series
which is a much better design (we do not know of a failure yet!).
Wobbly Side Stands, usually on
Boxers, can be a real problem, particularly on a well- laden bike. The cause is
wear in the 'ears' of the stand, and can be repaired by welding or replacement
- in either case, ensure that the frame lug is not also badly worn, as this is
difficult to repair with the bike the right way up. If necessary, fit a thin
washer to make up the clearance. Prevention is better than cure - oil the pivot
regularly, particularly in winter. Consider replacing the stand with a
"surefoot" stand. It may well be the cheapest cure.
Removing Your Engine?
The long mounting studs can be very tight - if so, do not try to drift
them out with a hammer, but apply penetrating oil, place packing pieces (large
nuts or piles of washers) below the one nut, and tighten it to pull the stud
out as far as possible; add more packing, and continue, using tube spanners and
packing if necessary. If necessary, heat the surrounding metal with a blowlamp.
Grease the studs before replacing them or play safe and replace with stainless
Replacing Steering Head Races? The outer
race (the one in the frame) can be very awkward to remove, there are three
basic ways. The first is using the correct BMW tool (which can be hired from
the BMW Club). The second is to drill two small holes in the frame so a punch
can be inserted, and knock the bearing out. The third is to apply two small
beads of electric weld to the race; the contraction of the weld is usually
enough to loosen the race. Don't try to drive the stem out of the lower fork
yoke after heating it up, as is usually advised. The stem is not shrunk into
the yoke, but is pressed, cutting paths for its fine splines as it does so.
Unless suitable tools are available to press it in and out (replacing it in the
same position, to ensure that the steering lock will engage in the usual place)
it is preferable to grind away the inner race of the lower bearing until it can
be split off with a chisel. Heat the new inner race to 200'C.
R45/65/65LS/80ST Owners -
would you like another gallon or more of fuel, a little protection for your
knees on cold days, and two fuel taps so that going onto reserve is not like
turning the ignition off. Fit a standard R100GS fuel tank - it fits perfectly,
but is an inch shorter than the standard tank, so the seat will require some
modification, but it is well worth it, particularly for the short-armed!
Commuting on a Boxer with a
dipped headlamp can leave you with a flat battery after a week or so - maybe
less if you have a small battery - but a good answer is to use a 20 watt
halogen bulb in the pilot lamp position. The 20 watt bulb is as bright as a
headlamp, but does not dazzle other drivers. RS and RT owners will need to
connect the existing (but unused) holder in their headlights to the parking
lamp circuit. We also recommend replacing the standard voltage regulator with
the higher output one. This is done by the Police because of all the extra
electrical equipment on their BMW's.
Ignition Advance Units can become sticky with age,
their springs then being unable to fully return the bobweights, causing a fast
idle and low-speed pinking. Many owners have found these problems recur soon
after cleaning and lubrication, the problem being that the 'lubrication' was
with WD-40, the limited lubrication properties of which soon evaporate with
heat! Always use a thin engine oil, don't forget the bearing between the cam
and its spindle, and, in the case of all post-'78 models with the 'beancan'
enclosure, the outrigger bearing above the points, or Hall Effect trigger, as
Does Your Boxer
Neutral Lamp Flash when the clutch is disengaged? This means that the
diode in the starter relay circuit has failed, and is short-circuited. The
diode is built into the contact plate at the back of the headlamp shell (all
twin-shock models except R45/65), contained within a black plastic cylindrical
housing, plugged into the wiring below the starter relay (pre-'81 R45/65), or
contained within the starter relay (all post-'81 R45/65 and Monolever models).
Can't Start Your Boxer
in Neutral? If you can only start by disengaging the clutch, but
everything seems to work as it should, the starter relay diode has failed,
becoming an open circuit, and must be replaced, as above.
Monolever Series Lights (from
1987) can all come on when the starter is operated, or when 'P' is selected at
the lighting switch! In either case, the culprit is one of the two tiny diodes
inside the Lighting Relay - replacement of the individual components is a job
for an expert, so if in doubt replace the relay.
Poor Pick Up of Bing CV carburettors can often
be traced to blockage of the two pick-up orifices sited at the base of the
carburettor body, on the engine side of the throttle plate; clear them with a
piece of thin wire or better still, a 'Primus' blowlamp pricker.
High Fuel Consumption on Boxers
can be due to the atomising air supply being blocked by sludge blown out of the
crankcase breather into the inlet elbows. Examine the pilot air jet (the brass
jet is at the lower inlet end of the carburettor), the atomising orifices in
the upper part of the pilot jet, and those on the mixing chamber which
surrounds the needle jet; while doing this, blow through the associated air
galleries from the inlet end of the carburettor.
Do Not Try to replace the needle jets of Bing CV
carburettors while they are still mounted on the engine! The needle jets and
mixing chambers will fall out easily enough, but the needle jet cannot be
centralised properly by pushing it up from the bottom of its bore. In such
circumstances, any attempt to tighten the main jet holder will result in a bent
needle, or even a split carburettor body. Take the carburettor off, and invert
it to fit these items.
Starting, immediately followed by cutting out, can often be caused by a
partially-choked cold starting jet. These jets are fitted in the bottom of the
float chamber, at the base of the auxiliary chamber from which the starting
carburettor draws its fuel. Their purpose is to restrict the rate of fuel flow
immediately after a cold start, so automatically weakening the mixture. Should
even one become partially blocked, that cylinder will not continue to run when
cold and the engine will usually stop. Remove and clean these jets,
particularly if the float chamber shows signs of corrosion due to water ingress
A Fire Risk has
existed on RS and RT models for years, where the lateral fairing bracket passes
below the fuel tank. The captive nut on its frame clamp has sharp edges, and
the main battery cable is usually pressed against it, just above the engine.
Several machines have burnt out from this cause, and it is virtually impossible
to realign the battery cable. Either insert a piece of rubber sheet over the
cable, or do it properly, and exchange the positions of the battery cable and
the adjacent small auxiliary cables.
Early /5 and /6 Series models have a headlamp
flasher which is unfused, and live at all times. It has caused the odd fire -
usually when unattended and should either be reconnected to the fused ignition
circuit, or fitted with its own fuse.
Flooded Your K? The electronics will always provide
enough fuel for a cold start, but supply of a matching quantity of air is up to
you! In very cold conditions always hold the 'choke' at full travel, and if
necessary open the throttle a little also, but be ready to shut it when the
engine fires. Lots of failed attempts to start will flood the engine and wet
the plugs, so don't rely on just tweaking the throttle a bit for cold starting!
Can't Get At Your
K75/100 Battery? The instructions in the manual are not too good;
remove both side panels, and pull out the plastic pin on the offside of the
injection unit. Pull the unit out to the nearside, until the multi-pin socket
is visible - you will then be able to see the retaining spring clip, and lever
it away from the socket, which can then be removed. The plastic tool tray
holder can then be pulled out between the frame tubes.
Remember to Change your brake
fluid every year or so it's easy, even on a K with ABS. As well as
keeping your brakes in top form, it will remove water and debris, so preventing
future problems, and maintain full braking efficiency. Always use DoT4
specification fluid, which maintains a higher boiling point when contaminated
by water than does DoT3.
Rear Crankshaft Seals on pre-1978 Boxers were
originally white in colour, and deeper than the later black seal. The white
seal is now unobtainable, and when fitting the later seal in an early
crankcase, take great care that the seal is not driven in as far as it will go,
so that its lip is in the same position as was the original - measure from the
crankshaft thrust bearing, which is visible behind the seal, and make very sure
that the seal is square with the crankshaft axis. The best answer is to fit the
seal on top of the special spacer ring which is available from BMW Owners Club
for this very purpose!
Adjustment of Steering Head Races is easy, even
without the special tool. Tighten the adjuster until, with the lock ring or
bolt fully tightened, all play in the bearings is removed, and a very slight
stiffness can be felt around the mid position. When slowing from about 40 mph,
rest one finger on the twistgrip, and note the speed at which the bike begins
to roll from side to side; if this roll occurs at more than about 20 mph the
races are too tight, and should be slackened in increments of about 3 mm at the
edge of the adjuster ring.
Pick-Up in Boxers is often traced to blocked pick-up orifices; this
pair of tiny holes are sited in the bottom of the main venturi passage of the
carburettor just on the 'downstream' side of the throttle plate. Make sure that
they are clear by use of a Primus blowlamp jet pricker or similar. Oil on a
Boxer Clutch is not necessarily a sign of a failed rear crankshaft seal - it is
more likely to be caused by a failed '0' ring at the end of the flywheel bore,
or on post '81 models inside the flywheel cap. This ring prevents oil pressure
from the rear main bearing creeping between the flywheel (or cap) and the tail
of the crankshaft, so exiting around the flywheel bolts. Always change this
o-ring when removing the flywheel.
Loss of Clutch Adjustment on pre 81 twins, can
be attributed to the clutch release bearing failing. Early replacement is the
only answer, as swarf from the bearing can get into the gearbox. When replacing
lubricate the bearing well, and ensure that there is free play between the
actuating arm on the back of the gearbox and the pushrod. Check this freeplay
regularly as clutch wear reduces the play.
Removing Rocker Arm Bearings, to remove the
rocker arm bearings, select a washer slightly smaller than the outside diameter
of the bearings, then using a long bolt and a spacer or socket draw the
Piston Rings. On all boxer engines, never fit an oil control ring gap
facing down, as when the engine is stopped after a run, oil can collect in the
bores and seep through the end gap. Also remember to separate the three gaps to
Gearbox when removing a gearbox from a 2 valve twin, there is no need
to remove the engine, just disconnect the swing arm and move it rearwards,
remove the battery carrier and remove the clutch arm, this should give you
enough room to remove the gearbox.
Brass Fairing Rivets rather than attempt to peer over
the brass rivets on RS and RT screens with a hammer, just insert a BA screw
through the centre of the rivet then a washer and nut, tighten the nut, the
action of which will peer over the end of the rivet.
Replacing Tank Badges rather
than gouge your paint work removing your old self adhesive tank badge with a
screw driver, simply cut it off using dental floss, by inserting the floss
behind the badge and work the floss backwards and forwards with a sawing
Problems when setting the ignition timing on all two valve boxers
always check it with a strobe on the max advance mark, in many cases it will be
over advancing due to wear in the ATU unit, thus causing the pinking. If this
wear is not excessive retard the ignition slightly to align the marks.
Contaminated Clutch Oil on a Boxer Clutch is not necessarily a sign of a failed rear crankshaft seal - it is more likely to be caused by a failed ‘O’ ring at the end of the flywheel bore, or on post - ’81 models inside the flywheel cap. This ring prevents oil pressure from the rear main bearing creeping between the flywheel (or cap) and the tail of the crankshaft, so exiting around the flywheel bolts. Always change this o ring when removing the flywheel
A NOTE OF CAUTION ON THE 8 VALVE BOXER TWINS Oil on a Boxer Clutch is not necessarily a sign of a failed rear crankshaft seal - it is more likely to be caused by a failed ‘O' ring at the end of the flywheel bore, or on post - '81 models inside the flywheel cap. This ring prevents oil pressure from the rear main bearing creeping between the flywheel (or cap) and the tail of the crankshaft, so exiting around the flywheel bolts. Always change this o ring when removing the flywheel