Setting
Valves
Alignment of the rockers,
end clearance, etc.)
setvalves.htm-40
Please read the valves.htm article
Do NOT take my advice to
read the that article lightly...DO IT!
What
follows starts with an extensive discussion of the background and
details; and then follows up with the actual procedure, in a
simplified version, and then a full version.
Background:
The airheads have, some more, some less, rocker tips offset to
the stem end of the valve. The rocker, being offset, tends to
rotate the valve, adding life to the valve and valve seat. The
offset force also tends to wear the valve guides unevenly, which
is especially noticeable on the older plain bushing insert type
of rockers, used on the /5. A careful look at
the valve gear will show that as the rocker rotates to actuate
the valve, the forces will try to move the rocker up and down on
the rocker shaft. Any excessive up and down end play on the
rocker, which lines up against the rocker blocks (and shims on
1985+ versions) will create a LOT of noise. MUCH of the valve
gear noise (especially on the RS and RT, where the fairings
amplify the sound) is from that end play movement, and NOT, as
supposed, from the valve clearance. So theory
goes. It should be noted that
as the valve seat-to-valve contact area increases with mileage
(or poor valve job), valve noise will increase, sometimes
considerably. Please
read the quieting pads article.
IF the rocker does not contact the older style rocker blocks dead
squarely, there is excessive noise. It was possible for that to
happen on the /5 and /6 to about 1975.
Even more noise can come about as the rocker bearing (esp. /5
bushing) wears. Enough miles with excessive end play, and you may
find the later type of rocker bearing (needles) coming out. More
on that later herein. There was a bad batch of needle bearings
too, the ends were improperly crimped over. The
early style (bushing) will wear in an oval shape, making for a
type of noise that is NOT totally eliminated by any
adjustment. Misalignment
of the blocks affects oil flow more than noise, in that it opens
up a vee-shaped escape path for the oil at top and bottom, but
end play will result in a fair amount of noise, and this end play
can vary with engine heating during warm-up, where one cylinder
may be noisier than another, or even that reverse during longer
part of the warm-up!
There are some differences in the
rockers. The 1970 to 1973 had bushes, some 1974 had these
too. They tend to be noisier. The 1974-5 were the first of
the needle bearing versions; the next version lasted from 1976 to
1984, then came the shimmed type; which had narrower rockers to
compensate for the shim modifications. The
1974-1975 rocker blocks had a flat bottom support, sitting on a
round support in the head. These worked well, but were not
perfectly indexed to the head. It
is questionable that the rocker tips were heat treated, or if so,
properly. Tips can be resurfaced.
The 1976-1984 rockers had a cutout,
or a 'step' in the rocker blocks that mated to a machined button
in the head, and these index quite well, there is very little
movement possible, rather often there IS enough to enable the
proper adjustment of end play. The
tips of the rockers usually can (colorization) be seen to be heat
treated. The heat treatment is usually fairly deep, and
contrary to BMW School teaching, the rocker tips often CAN be
lightly resurfaced if need-be. I have ground them a fair
amount and re-heat treated them (oil quenched) although I advise
against re-heat treating. In 1985+ the support blocks
fit a bit differently, with a male round shape fitting directly
into the head, no button, and indexes very well indeed.
There is a plastic thrust bearing piece at the TOP of the rocker,
and end float is adjusted by shims.
Retrofittable to 1976+.
In fact, many of the parts of various years of /5 and up to 1984,
are interchangeable in some way. The 1985+ valve gear can be
fitted to most; but I fail to see any great need to do that.
The 1976+ pushrods are better.
The
idea of shims, or adjustment of the end play by the movement of
the blocks (when it can be done on the rather early models, and
OFTEN on those up to 1984), is to have the rocker able to move
(rotate) horizontally in its normal movement FULL RANGE
without ANY binding, yet have the absolute minimum possible up
and down play. ...so....read the next paragraph!
NOTE: It is possible on /5 and /6
machines, especially up to l975) (and slightly on /7 and into
some 1984), to adjust the rocker boxes (squeeze them towards each
other) for zero ENDplay (just oil film
movement). That is the best adjustment. You do
NOT want to BEND anything, just set the endplay, so be
careful. Lots more later here.
BUT...it
is also possible to overdo this end play adjustment, have the
clearance too tight. The result is that at approximately
normal valve adjustment clearance there is enough END binding at
full lift to hold the valve open, almost defeating the tired
old valve spring. The resultant snap when the valve does close is
a loud clatter. So, perhaps I had better say it this
way: it is necessary to TEST move the rocker over a WIDE
arc to test for any binding, so, to do THAT, you must back off
the valve adjuster relatively fully in order to be able to move
the rocker arm in that wide an arc....this is done each time you
ADJUST the end play (which is seldom).
Generally
we say that in moving the rocker up and down, you should only see
the oil film move...at the junction of the rocker and rocker
block. Again, you should check for any binding or excessive
friction over a wide rotation...with the adjuster rather fully
backed off. From 1985, end play is done by actual
measurement, but the oil film check is applicable if you want
to. 0.001-0.003" is an acceptable range if
you are measuring, on 1985+ valve gear.
From 1985 BMW revised the rocker mounts and
incorporated shims & plastic inserts into the ends, the shims
are available in several sizes. I'm not a great fan of plastic
inserts. I am also not a fan of the shortened rocker arms, and
the shorter bearing to bearing distance. Depending on
your year bike, to convert to the l985 and later version can be
VERY pricey (for NEW parts).
The BMW bulletin on this is from May 1986 11-032-86 (2208), which
also covers in depth the 1985 R80 rocker arm assembly
changes...which I suggest not be done unless you have a big
wallet or access to used but good parts at a cheap price.
Here are the part numbers for the shims, used on 1985+ valve
gear:
The rocker SHAFTS should be installed such that oil, coming
from the engine casting from holes at the top of the two top
cylinder hold-down studs, and traveling outward along those
studs, gets into the valve gear....where it gets into the rocker
bearing and also leaks out at the rocker block junction to the
rockers,, and then some fumes and oil lubricates the
guides....sort of....and the excessive oil flows down the pushrod
tube holes to the cam followers (lifters), and the cam lobes, and
downward to the pan. If the rocker shaft is not installed
properly on some models, you will not get oiling. There
are exceptions, and we could discuss the drilling of the rocker
shafts, etc...but....rather than get into this deeper, because
knowledge of the exceptions is NOT necessary, and because you
could figure it out from a visual inspection......please
simply follow my advice here:
1. This is what BMW did: BMW marked
the shafts in one or two of three ways. There may be a
colored...perhaps better to say different metal color...in the
middle round area on ONE end of the rocker shaft. There may also
be a punch prick on that end. There may be an OFFSET of the
center punch prick.
2. This is what YOU DO:
In every case, in every instance.....any markings are to be on
top, and if a punch prick is offset, that prick is AWAY from the
engine. If you do it this way, you will have NO
problems with things in the correct position.
A bit more on the end
play:
The early models were the ones that had so much slop available at
the rocker mounts/blocks, that the C-clamp method was more
needed...although many of us used brass or dead blow hammers,
VERY lightly. NOTE that Haynes, and I think Clymers too, shows a
jig, similar to the #200 BMW tool, that can be built.
From the 1975 year, BMW machined a STEP into the rocker end block/head junction area, and the blocks are supposed to be precisely machined such that no adjustment is possible. I find that not always so, particularly in the earlier versions. What you do NOT want to do is BEND the stud, so only light pressure is used in aligning rocker blocks...where this is possible. The /5 and early /6 are VERY adjustable....providing they are stock. Many folks have upgraded to some extent or other. Even as late as most 1984 models I have found a bit adjustable! When setting up the early valve gear, be sure to look at everything during the alignment...do NOT just pay total attention to end play, DO check that the rocker tip is offset on the valve stem, that the rocker rotates without binding or excessive friction over its full rotational range, and check that the rocker ends are flat to the rocker blocks....and check the movement of the pushrods during engine rotation, for any binding in the head holes.
In the 1985 and later valve gear setup, the rocker end blocks are fitted rather precisely, and you will gain nothing trying to squeeze the blocks together...AND these 1985+ models are to be shimmed for end play. On the late /6 , the /7, and up into 1984, you can try, but do NOT bend anything....LIGHT pressure on any large C-clamps!...and NOT on the rocker shafts, only the blocks! Pressuring the rocker blocks strongly with fingers during tightening of the nuts is OK, as is using a large C-clamp with common sockets, selected to NOT bear on the rocker shaft, but only on the rocker blocks. Do NOT use hardly any force with this C-clamp! OF COURSE>>>The two nuts that hold the rocker to the head must be loosened some to allow the rocker blocks to move that very tiny amount that MIGHT be possible! Yes, I have seen someone try to adjust end play with the rocker nuts fully torqued.
If you have a C-clamp with an opening big enough, you can use
some sockets in your socket collection, one on top, one on the
bottom, with the C-clamp. Be
sure that the sockets do not rest on the inward round tiny bit
that projects. You can also get a
couple of THICK metal washers and grind the washers so they don't
rest on the round bit, yet are thick enough to be slightly proud
of the rocker shaft...thus the C-clamp can
be a smaller one, AND, the C-clamp will NOT press on the SHAFT.
For each rocker adjustment, simply loosen the 2 rocker block nuts
about 3/4 turn or so, affix the Clamp and washers/sockets (or
affix them first), and make an estimated end play squeeze (not
much!), and then torque the nuts a bit...then recheck end
play. If correct, torque the nuts to the normal 25
footpounds. Do NOT let the nuts be loose for more than a
FEW minutes at a time. If they squeak on tightening, loosen
and OIL the threads. The 4 stud nuts are
normally torqued with oily threads.
NOTE! There were TWO
generations of /5 rocker
blocks: split and non-split.
The earliest were the NON-split type
and were essentially the same as the /2 design. The blocks were a
press-fit onto the shafts, and the
end-play could be adjusted by using a c-clamp and socket method,
with a bit more pressure from the C-clamp method I have
previously mentioned. The SPLIT types
were to reduce cost in manufacturing, and
allowed some hand adjustment without a c-clamp.
The Matra #200 tool was discontinued by BMW in 1973, and it's use was NOT recommended, as evidenced by a 1974 factory service bulletin to that effect. The tool would make the two rocker shafts parallel to one another, which served no value. THUS......I do NOT recommend using NOR MAKING, the /5 valve gear alignment tool shown in some BMW literature, and in some Haynes and Clymer's literature!!
BMW's better and later design involved
hand-locating the rocker so that the rocker tip contacts the
valve tip off-center, and the pushrod was located as high in the
pushrod tube as possible while keeping it centered in the tube. An
often hidden cause of noise is the pushrod hitting the head near
the head gasket joint. Later modifications to the valve
gear, like the stepped blocks, were done to make it harder to
inadvertently miss-align everything. If you are setting up
a pre-1985 airhead, setting up the pushrods and rocker block and
rocker tip alignments, and rocker end-play, you can do it all
manually, with just barely loosened rocker block nuts...so the
blocks can be moved slightly. The movement is hardly
noticeable, except for the oil film rocker end play test. The
very earliest rocker gear (/5 as example) can be moved all over
the place, and one must pay attention to rocker tip, and
squareness to the blocks, etc.
I sometimes use a very large slip-jointed wrench in doing
this pre-1985 end play adjustment job, after I hand-align
closely. I also use either that wrench or a huge
C-clamp (and sockets or specially hand-ground washers) for the
end-blocks. DO keep in mind that from 1975 to 1984, the
amount of available movement of the rocker blocks can be quite
modest, to near zero.
BMW made changes now and then in
the valve gear, and the final important change was in August
1984, when the shims and plastic insert were incorporated. The
rocker arms width was shortened (poor
idea, less distance between bearings), and the needle
cages pressed in deeper, to accommodate this addition of the
plastic and shim setup. Because of this, I don't
REALLY like the later valve gear as well as the earlier gear (I
prefer the gear of the early 1980's).
****One must NOT use hardly any
force (except a bit more on earliest non-split /5 end blocks)
with the C-clamp and sockets or washers, and the early 1980's
models are barely moveable, but often just enough. You must NOT
bend the rocker gear by misuse of a large C-clamp and
sockets/washers. Because the use of the "C-clamp
and sockets/washers" method can create some REAL problems
from excessive force on the C-clamp, I think it BEST that most
folks simply do NOT use this method, unless they are quite
careful. It is pretty easy to do the job with big slip-jaw
pliers OR the C-clamp. Just be cautious....and have the two
nuts loose enough.****
Here is another method:
On post-1975 models with the stepped blocks, with the valve
clearance adjuster backed nearly fully off, try loosening the 2
rocker nuts a turn or tad less, then use fingers or a light tap
with a plastic hammer or soft brass hammer...to move the blocks
toward one another while snugging the nuts relatively evenly to a
FEW ft/lb with a box wrench. Bit by bit. Check
the end play, and if it's too tight, tap on the rocker arm gently
to get a minimum of play, rotate the rocker through its full wide
arc, double checking. Then torque the head normally, to a
KNOWN ACCURATE 25 footpounds. REcheck.
Finally, examine the alignment by eye, and if everything looks
OK, adjust the valve lash. Do NOT leave the cylinder hold
down nuts loose for very long (two per rocker, one rocker at a
time)....I believe that TIME can cause the head to warp in
somewhat the same way as if you did not tighten the head with the
6 nuts in a cross-pattern. Thus, I do this
job within a few minutes at most on each rocker, engine
cool.
Pushrods:
It was around 1977 that BMW changed the pushrods to a multi-part
design, incorporating some sort of aluminum alloy center section
that expanded closer to the rate the cylinders expanded. Their
lowered weight also helped offset the mass of the larger intake
valves for the 77 US R100S and R100RS models, and the reduced
diameter reduced any likelihood of the pushrod hitting the inside
of the head. The pushrods were not, however, redesigned again for
the Nikasil cylinders, probably the factory found out that the 77
redesign was adequate. The tappets and rockers got changed
too. One could now use a bit closer valve clearances, noise
was supposedly reduced some...especially cold to hot. BTW...it
was in '81 (a questionable date) that the pushrod tube collars
became unmoveable...so that was no longer the method of
tightening the pushrod tube rubbers for elimination of
leakage. That fact is not shown in some Haynes and
Clymers. There have been reports of the collars
being brazed in position on the pushrod tubes far earlier than
1981. I believe the collars should generally be left alone.
NOTE that the later valve gear items are applicable to
earlier models. Don't think about just using the shims,
unless you intend on machining the rockers, as the early ones
need to be shortened. I have the bulletin describing the parts,
procedure, etc. to update to 1985+, the shortening is not part of
it; you are supposed to purchase new rockers (or get the kit
which contains them). All-in-all, unless you
can get the parts CHEAPLY, it is probably a waste of time and
effort to get the later valve gear. Frankly, I like
the early 1980's gear better.
Background, history, hints, other information, some of this is repetitive, told in another way:
BMW did a lot of things to quiet the
valve/rockers noises over the years. Most of the noise is NOT the
rocker hitting the valve stem, but the rocker end play or ovality
on the bushing type of rocker, or, gads, extreme wear or missing
needles. Noise can be particularly annoying on a RS
or RT, or any model with a fairing. Having aluminum heads and
fins does not help for noise.
There are rubber noise silencing pads available. Quietingpads.htm
These are a special silicone rubber and last a
long time. They help even on those heads that have the
factory roll-pins for strength improvement and noise reduction.
The early /5+ bikes had the rocker blocks very loosely fitted to
the cylinder studs, and they could be moved around a fair amount,
and thus could be adjusted. If the bushings are well-worn,
replace them, or you are fighting yourself. Adjustments:
1. squaring-up and centering of pushrods
2. positioning the rocker to hit the valve off-center to ensure
valve rotation
3. end play.
A jig that squares it all up...rocker to rocker, which means
almost nothing!.... but is easy to use... is described in Haynes,
and perhaps Clymers, and some BMW literature. I say DO NOT use
such a jig. Most folks do not have the jig, and
align things with C-clamps and appropriate sized sockets, and/or
maybe a small brass or other dead-blow hammer or a large slip
joint pliers of some sort. FRANKLY
the jig does NOT do all of what you NEED, and I recommend NOT
going to the hassle of making one up. The jig is not even
good for SQUARING the rocker shafts/blocks up too well, but
aligns the two rockers parallel...which is of no meaning.
Later, BMW machined a supposedly precise 'step' into the bottom
of the rocker blocks. You are not supposed to be able to adjust
those, but in practice many of the earlier ones ARE adjustable,
up into 1984. For this, Do NOT
bend the mounts/studs with over zealous use of a C-clamp
(or?). VERY light pressure only, with the two stud nuts
loosened for minutes only!
The ends of the rockers that butt up to the rocker blocks can be
polished very carefully, for a slight reduction in noise, if you
are plenty anal about valve noise. VERY
carefully...and NOT rounded or done on an angle. If you cannot do
this squarely, don't try, you will make things worse!
The
PROPER amount of end-play on a rocker is such
that with the cylinder at TDC (OT) on the compression stroke for
THAT cylinder, and the rockers having clearance from the valve
stems, you lift the rocker UP AND DOWN...and should not hardly
feel anything, but you can see the OIL
FILM moving. The proper amount of bearing wear
play is negligible, and tested for by TWISTING the rocker against
its shaft. Zero play is nice. To check for that, you need
the adjustment backed way off. Under NO circumstances
should the rocker, with its adjustment backed nearly completely
out, have any noticeable friction whilst being rotated through
its entire range of possible movement. That means that it
IS best to loosen
the valve clearance adjustment quite
a bit, if not nearly fully, and
check that the rocker is free, no real friction, over its normal
TURNING travel, and then some, when setting end-play.
It is probably safe to loosen the two rocker nuts a turn
or tad less for the end play adjustment (unless shimming) but
don't leave them loose overnight. Use 25 ftlbs for the final
tightening. Non-Nikasil can go up to 30 ftlbs or so but I frankly
do not go higher than 26 myself, liking the safety factor.
Pulling a stud out of the crankcase ruins the day. If the nuts
squeak, remove, oil, reinstall. Yes, the threads are to be
torqued OILED. That applies to the 4 rocker nuts, although you
can clean the 12:00 and 6:00 head nuts and studs and use a trace
of oil on the threads.
If you take the rockers apart; there are more than one style; you
can loose needle bearings onto the floor or you can have worn
bushings on the early models that should be checked. Really badly
worn bushings can be felt, usually, by twisting the rocker with
your hands, back and forth, easiest to do with the valve
adjustment quite loose. Shims
can be added to older models (before the 1985 update), but the
rockers need shortening for the full conversion, I recommend
AGAINST that.
If your rocket shafts have markings...punch prick or round insert
marked area, those are ALWAYS on top, and if the mark is offset
on the end, that mark faces the valve cover. Failure to
heed this advice can, on some versions, result in no rocker shaft
oiling....and not enough oil in the valve guide, etc.,
area. NOTE: Here is the part I
did not get into in an earlier discussion, at the early area of
this article, and I will touch on it lightly here: That
early statement is not 100% accurate, later versions of the
shafts have one angular drilling, and CAN be fitted with the mark
facing the engine or the valve cover. A shaft inspection
will show this. Some folks rotate the offset marked shafts
180° to allow them to have additional life. DO
NOT do anything unless you inspect the parts, to be sure about
YOUR oiling!
BTW....The later valve covers are handed.
Marked L and R, on top, near the spark plug.
Installing them wrongly will have the valve cover fins not
properly parallel.
Simplified valve adjustment information:
***Valves are adjusted with engine cool, meaning baby bottle temperature OR LESS.
To do a valve adjustment, you'll need an old baking tray or catch pan and newspapers, bike tool kit, ACCURATE torque wrench with socket to fit the nuts (If at this valve adjustment time you intend on setting the torque on the studs and head...not required often, actually). Typical intervals for valve clearance checking, and possibly adjustment for an airhead are at initial engine build or top end rebuilding; then at maybe 100 or even 600 miles; then if the valves were relatively stable, maybe at 2000, then every 5000. Check the head nuts (6) torque AFTER you check the valve clearances and write those as-found clearances on a chart...which may come in handy. The 6 nuts should have their torque checked at initial rebuilding (of course!), then at each of the next few valve checks. Usually by 5000 miles or so, the torque remains stable, and then maybe you can check at every 30,000.
Some of you may need a pair of sockets
or the very thick and slightly modified washers I have described
earlier in this long article....to fit properly over the rocker
boss ends, that is, they are going to be used as spacers if using
the C-clamp method, so the proper size fits over the end of the
rocker shaft, but does not grip it, and certainly is not so large
as to not fit squarely on the rocker block end. The washers or
sockets MUST not be in contact with the small curved in portion,
and the washers must be thick enough, and perhaps ground at one
point underneath to avoid that rounded bit mentioned.
Those having bikes from 1985 will NEVER use a C-clamp, as
those...or early ones converted to use all the 1985+ parts;
have the end play of the rockers set by shims and the rocker
blocks are NOT adjustable, being set by more precisely milled
steps. Keep in mind that any of the models before the 1985+
version MIGHT be adjustable slightly, and the /5 and /6 certainly
are. Your tools should include feeler gauges, you
might want to have the go, no-go type, your choice.
Valve adjustment.....IN DEPTH:
FIRST!, note the following: At every valve adjustment interval, before doing anything such as checking head nut torque (if being done), etc.....during the procedure, at compression stroke at OT, measure and write down the clearance at the valve tip, to keep a record, for enabling you to follow trends over time.
Rocker shaft end-play: You should check the end play before finalizing a valve adjustment. All this amounts to, NORMALLY, is to have some valve tip clearance, and lift the rocker up and down and look at the oil film. DO NOT make any actual adjustments...including NOT adjusting nut torque... until you measure and write down the clearance at the valve tip, to keep a record; enabling you to follow trends over time. The cylinder to be adjusted MUST be at TDC (OT) on THAT cylinder's ""compression"" stroke. On the original /5 and early /6 valve gear, the rocker boxes are awfully free to move around until the nuts are torqued down. The rocker blocks can move around a tad on SOME later models too, but not on the ones from 1985. Generally, after the /6 the movement is little, but enough. Some folks have put some or all late parts on early bikes.
Once end play is properly set, only if such an adjustment is necessary should you loosen a rocker assembly's two nuts to adjust it for end play. You don't want to loosen much for too long, the head/gasket might warp a bit and not seal to the cylinder properly. SOME experienced Wrenches say to only loosen ALL the 6 nuts for this sort of thing. I say no, just don't leave the nuts unequally torqued for more than minutes.
Remember that the heads are normally tightened in a cross pattern, and in STAGES of increased torque...like 11, 18, 25 ftlbs, and if more than two rocker nuts are loosened you must do that. Therefore I normally do JUST one rocker at a time...so no need to loosen more than 2 of the nuts. Some folks loosen only one end and use a light hit from a brass (or other dead blow type) hammer on the rocker BLOCK or onto a non-shaft-touching socket, to close up end play, keeping it square. That works out OK sometimes, once things are rather close to being correct. Clymers and Haynes have sketches of a nice alignment jig, if you are anal enough, make two, and give me one to replace my missing one....again, that only squares up the rockers to each other on the /5...I used mine on some /6 bikes, with a small amount of help, only. Frankly, again, I say forget that jig. (don't bother)
HINT:
There are two nuts, one at 12:00 and one at 6:00, holding
the cylinder head to the cylinder...those should be left at
full 25 footpounds of torque, whilst doing the rocker end play
checking...I have never found a problem doing it this way, and
the advantage is keeping the cylinder head tight to the
cylinder. This is in disagreement with factory
recommendations. NOTE, however, that I add this following
caution: It is a good idea NOT to allow previously torqued nuts
to be left loose for more than a few minutes. I have had
strong disagreements from some experienced Wrenches on this
point, but I have NEVER had a problem, NOR heard of
one. ALSO note that I loosen ONLY the two nuts on ONE
rocker, and do that ONE rocker at a time...retorquing to 25
footpounds before doing the other rocker.
WHAT is the proper end play? WHY
is it important (not overly, actually)?
The normal operation of the rocker is a SIDE AND ANGULAR THRUST, hence the rocker can move up and down with considerable force. Excessive end play wears things, and is prime cause of noise. If the play was REALLY excessive, especially on the old /5 machines, you will have faster wear on the old bush style rocker bearings. The valves are not as stable in operation. The valves are NOISY with even a wee bit of excessive play. The vast majority of 'noisy valves' is play that is excessive. BMW made a LOT of changes over the years to quiet the valves. Valves on the faired models sound far noisier.
With the valve tip clearance adjustment VERY loose, perhaps
nearly fully, grab the rocker and try to move it up and down, and
then try again with a slight twisting motion. You will need a tad
of force here. What you are looking for is no appreciable up and
down; just, perhaps, visibly seeing the oil
film move at the junction of the rocker and rocker
block/shim move, very slightly. If the rocker moves freely in the
normal valve actuation direction, FULLY, through the FULL range
of turning motion possible; and yet only an oil film movement at
best is seen up and down, you have the proper end play. It will
NOT tighten up as the engine warms up. A side twist
is a quickie check to see if the bearings (bushes on early
models) are OK.
Assuming the type without adjustable shims (if shimmed type...
this procedure needs modification, of course, and you will need
shims):
First loosen the TWO nuts....probably
about 1/2 to 1 turn, for ONE rocker assembly shaft/blocks.
I prefer to use a couple of 3/8 or 1/2 drive sockets from my toolbox, carefully selected for size is such that they fit OVER, not touching/grabbing, the rocker shafts,,,,and are thus bearing ONLY on the rocker blocks themselves. I also have made up thick washers for this purpose, for use with my slightly smaller C-clamp. I then use a C-clamp or huge slip joint pliers, to put a little bit of pressure on those sockets or washers...not very much! Squarely. You are slightly squeezing the two end blocks together...you are NOT to squeeze on the round shafts!! Do not use force wrongly. Do NOT try to bend things! If you are wary, or have no large C-clamp and appropriate sockets, use a dead blow hammer...lightly! THEN tighten the rocker end block nuts some.....perhaps a couple to 4 foot pounds...LIGHTLY is fine. Recheck that the rocker will move without friction or grabbing in its normal direction of movement, FULLY! Remove C-Clamp if being used. Torque back and forth evenly to the normal 25 ftlb torque, and recheck for smoothness and end clearance again. The rocker MUST have minimal end play, yet no real friction, for the FULL range of motion possible from opening and closing the valve. This is why the check is done with the adjuster very loose, almost completely loose.
The clearance at the valves has to be made with the engine cool and the nuts at 25 footpounds. If re-torquing a head, back the nuts half a turn and then torque in the tightening direction. Squeaky?...OIL the threads. Note that except for the first few thousand miles, re-torquing is not necessary very often, certainly NOT at each 5000 mile valve adjustment check. IF re-torquing, re-torque them evenly, in a cross pattern. Use an ACCURATE torque wrench. First loosen the nuts by rotating COUNTER-clockwise about 1/4th or 1/2 turn. The 2 cylinder head nuts seldom change any, whilst the rocker 4 nuts may change a little bit. Then re-torque ...use 25 foot pounds, all models (yes, I know the early bikes can be set to 29-31 in some books). If ANY of the 4 nuts squeak, remove just that one ...and oil and retorque. Repeat for any other squeaker. Remember there are 6 nuts, 4 at rockers, one near spark plug, one below. THEN, set the valves, IF they need it. I always recommend writing down the valve clearances, for your records, before you re-torque and then after you set the valves. Always lift the rocker and check the end play....the oil film movement.
Of SEVERAL methods of obtaining OT and setting the valves, my personal method follows:
Have the bike on the center-stand, then jack up the rear frame cross piece just enough to get the rear tire just barely off the ground. Frankly, most of the time I just put my right knee under the muffler, from the left side...although I HAVE used my modified cheapo Chinese bottle jack at the crossover frame tube. yep...that was a hyperlink.
Remove timing hole rubber plug. That hole is near the dipstick. Remove the valve covers slowly, to avoid ripping the 'they last forever' stock gasket. Some of you may have the soft silicone gaskets, some swear by them for sealing irregularities and warpage. I won't use them. NOTE that you NEVER oil the stock gasket OUTER surface, in fact you want it wiped with a cloth when replacing the valve covers, as oil, especially petroleum oil, can carbonize and act like glue, and the gasket can come apart on the next cover removal. Frankly, I DO FAINTLYoil JUST THE HEAD SIDE of that stock gasket (if an old used one)...that helps, over time, to slightly stick the gasket to the HEAD; which is what I DO want. With a NEW gasket, I have all surfaces dead clean and dry, as the head side of the valve cover gasket has a heat activated glue on it. Gaskets generally tear because the valve cover pulls the gasket in one area....being careful means never having to ever replace a valve cover gasket, and you always pull the valve cover off slowly and smoothly. REPEATING!....The valve cover gasket has a heat sensitive side. If you have a USED valve cover gasket you are re-using (they can last forever), coat the head side with dino oil before assembling; that will eventually carbonize, and help hold the gasket in place, helping to avoid its tearing, if you remove the valve cover too quickly. For a NEW gasket, clean and dry assembly of all surfaces.
***Don't lose the large flat washer under the center acorn nut (later models may have a waverly there), nor the waverly washer under each of the two 10 mm nuts, on each cover. That center stud is easy to strip out. Don't over- tighten that acorn nut. You can see, from vertical, viewing near the spark plug, if the stud is engaging EVERY ONE of the head's threads. If not, consider getting the slightly longer valve cover head stud BMW offers. That longer center stud, 70 mm instead of 65, and is installed with Red Loctite, and it must be flush, or very slightly protruding, on the inside (visible, near spark plug), or it is not gripping all the possible threads. M8 x 70 mm stud: 07-12-9-908-142
Put the transmission in top gear (4th or 5th), and rotate the rear wheel in the NORMAL direction, using the gears backlash...in other words, jerky back and forth, always trying to move the engine in normal direction, until the LEFT INTAKE valve, the rear valve, is coming OUTwards...that means that valve is closing. I then continue small jerks, still in the forward direction, until the flywheel marking OT is in the timing hole window. I then take LEFT side valve clearance measurements, writing those down on paper for future reference. Use the feeler gauge at the valve tip-to-rocker; whilst placing a bit of thumb pressure on the adjustment end of the rocker (to take up oil film play).
Depending on mileage from new valve job or since last adjustment, I MIGHT torque the heads to 25 foot pounds, or I might set the rockers end play. I am NOT a believer in doing those very often. I will try to move the rockers UP and DOWN, see if just the oil film is moving, and no more. I might look at the rocker-to-valve end contact, see if it is off center. If I want to be really thorough, I will check end play, rocker twist play, rocker tip on the valve tip, pushrod clearance, and rocker rotation through the full range (adjustor WAY backed off), pushrod fit, etc.
You can now rotate the left cylinder push rods, they should rotate smoothly, and have absolutely ZERO tightening and loosening or other funny feeling as they are rotated. This is a very rough check for them not being horribly bent. The only true check is to remove them and roll them on a flat piece of glass or a surface plate. They do not usually bend unless exceeding redline rpm a bunch, or from some top end malfunction.
I set the clearances to .0045" intake, .0085" exhaust, with pressure on adjustor end to take up oil film slack. That is equivalent to an easy smooth fit for the .10 mm and .20 mm metric feelers, same for .004" and .008" feelers. The R65/R45 models probably should have the valves set a wee bit looser, .006" intake and .010" exhaust is fine. There is nothing wrong with using .006 and .010 on all the various models, actually, and a case can be made for some slight benefits, at the expense of a VERY SMALL amount of noise and potential wear. Be VERY sure you are not only at OT, but are at OT on the compression stroke for THAT cylinder.
***For a FRESH valve job during initial first break-in miles,
or for those having valves that are closing up fast (perhaps
faster than .002" per 5000 miles on a well broken in
engine), you could consider using Intake .006" and Exhaust
.010" even on the larger engines, even a bit wider if on a
R65/R45 (they are NOT overly prone to special closure
though). No hard and fast rule here. You do NOT want
all the clearance EVER taken up
during riding, that can cause SERIOUS mechanical
problems. NOTE that it is the exhaust valve that
tends to close up, and once either of the valves has closed up
some, the engine may be hard to start. There is a big
article on this website on the valve and seat problems.
Read it. valves.htm
Note: If the
valve seats were replaced, keep a close eye on the valve
clearances, check them more often, for maybe 5000 miles.....there
have been instances of the seats moving; particularly if not
installed 100% perfectly, a tricky job on a BMW Airhead.
What about
an airhead where the clearance is constantly changing...getting
tighter at each valve clearance check?....and I mean more than
maybe 0.002" each time:
Once the clearance adjustment is fairly well used up, you are going to want a valve job, rather than a blown up engine. This using up of all adjustment is NOT a definite criteria, exhaust valves have gone into pistons WELL before that point. This sentence probably applies more to the original valve seats up through 1984.
Hints on measuring:
MEASURE valve clearances by using one thumb on the pushrod (adjustor) end of the rocker arm...with some moderate thumb pressure to take up oil clearance, etc......and trying to slide a feeler gauge, SQUARELY without any real force, at the valve stem end. You need TWO wrenches to adjust the valves. I prefer a box end wrench for the locknut, and a open end wrench for the adjustor. The box end wrench loosens the locknut very slightly. The open end wrench is used to adjust the special cupped screw. Tightening the locknut tends to rotate the adjustor, hence the use of two wrenches and a bit of care...you'll get the hang of this very quickly. DO NOT over-tighten the adjustor and nut...snug is fine. If anal, you can measure the torque...12 foot pounds, do not exceed 15 foot pounds or bad things will happen. Usually the bad thing is stripped male threads, not too serious, as you just replace the adjustor, if you can easily get it out after stripping the threads. The adjustment needs to be tight...just not overly!
Assuming you
have finished with the left
cylinder, you can wipe any oil off the cover side of the gasket,
and reinstall the cover (do NOT over-torque the 3 cover nuts!),
and then proceed to the right
cylinder as follows:
Bump the engine forward
for ONE...JUST ONE,
360 degree revolution....back to OT mark again.
If you were watching occasionally during the bumping, you would
see the right
rear intake valve come outward, just like you did on the left
side. Now do the right side cylinder adjustments, etc., in
the same way, at OT on the compression stroke of the right side.
HINT: Some folks will remove spark plugs when rotating the
engine. As an old-time wrench, I am against
that, in the very off chance that a bit of carbon gets into a
valve seat, thereby upsetting the valve clearance measurement
& adjustment. Some rotate the engine by first
disconnecting all wires to the battery negative post (-), and
then removing the front cover, and then they rotate the
alternator rotor center allen bolt. I have even seen
front covers machined for a hole and rubber timing plug so the
battery need not be disconnected.
Poobah!
I am obviously not in
favor of those methods. I do NOT like that alternator bolt
tightened beyond the modest pressure needed in originally putting
the rotor on the crankshaft, which may happen if you try to
rotate the engine. You also should remove the spark plugs for
that adjustment. Other folks might tell you to rotate the
engine by whatever means, and have a finger over the spark plug
hole, wait until you get some pressure, then rotate further to
OT. Again, I don't do it that way. That will, of course,
work just fine.
***For bikes with kickstarters, you can, of course, put the
transmission in neutral and just use the clutch lever at the bars
to move the kickstarter into an initial engagement about 1/3
down. That avoids 'catching' the transmission internal gear teeth
edge. ... then use the kickstarter with your hand, to bump the
engine rotation. That negates lifting the rear tire off the
ground.
Some may tell you of other ways of finding OT ...without even
removing the rubber timing plug next to the oil dip-stick. Yes,
can be done, best 99% of you do not. Yes, the BMW camshaft has
slow rise ramps. Yes, OT is not critical.
Do it MY way...and no problems!
**NOTE: You MUST have the proper
OT for THAT cylinder...that is, THAT cylinder MUST be on
its COMPRESSION stroke, when setting valves!!
That is why you look at the intake valve. The intake valve
comes outward, closing the valve, and the piston continues,
starts to and does rise on the compression stroke, and the OT
mark appears.
When replacing the later style valve covers, they are marked L
and R, ON TOP, next to the spark plug area. Do not put them
on the wrong side of the bike, nor upside down. Two
reasons, varying by time and production and old-wives
tales....one was lining up the finning, the other for mechanical
interference.
WIPE the outer gasket surface and the valve cover, so that any oil between the gasket and valve cover surface, is wiped away. That will greatly help in longevity of the gasket. Otherwise the oil MIGHT carbonize, and the gasket could tear, at next cover removal. If the gasket is USED/OLD...and loose, you COULD remove it, and then finger-wipe oil on the INNER surface of the gasket, the part that fits against the head...you won't need to do that again...and it will carbonize eventually, a nice thing...you won't tear gaskets if you always wipe the OUTER surface when doing valve adjustments. Quite anal types can use oil on the side of the gasket towards the head, and FAINT silicon grease on the OUTER side of the gasket. Don't put anything on the head side of the gasket on a brand-new gasket....and the surface of the head and head side of the new gasket must be totally cleaned of any oil first.
Do NOT over-torque the two small 10 mm nuts (one wave washer on each, please), nor the center acorn nut (one thick or waverly washer). Whilst stripping one of these is not the worst of days, why not avoid it?
HINT! Many folks have problems replacing the small 10 mm hex nuts onto the two valve cover studs, especially the front one on the right cylinder head. Try a magnetized screwdriver to hold the nut flat AND SQUARELY on the stud end, and use a fingertip to rotate the nut. I am not a big fan of the fancier machining methods for allen screws, blah blah.
HINT (repeat!): inspect the length of the center stud...at the inboard end. If ALL head threads are not in use, obtain the longer 70 mm stud I noted the part number for, somewhat earlier here..... from your BMW dealership ....and install with Loctite RED.
HINT: It is NORMAL for the
rocker to NOT contact the end of the valve squarely!...this is
how the valve is rotated, by the rocker pushing on the valve stem
slightly off center.....lowering overall seat and valve wear, and
maintaining the best contacting of valve and valve seat.
(btw, the camshaft and lifter/follower, have the same sort of
offset, for rotation).
Revisions:
01/20/2008: Completely revised as a stand-alone article. Some items previously in this article were moved to sub-sections of article 60, and others were expanded upon and left in this article.