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MAIN SEAL Installation; oil pump & oil pump cover;
Crankshaft; front main bearing cap/holder/carrier; rod bearings;
Timing Chest Seals; Rod bolt tool; Grabby clutch, VIBRATIONS,  ETC.

Copyright, 2014, R. Fleischer

Article 60, sub-section 2


This is CRITICAL! Flywheel Removal/Replacement is the first item here!!

There are potential trouble areas when removing & replacing a flywheel (or, from 1980, called the Clutch Carrier).  First trouble area is the moving of the INNER thrust washer off its pegs, which YOU WILL PREVENT by the use of a crankshaft blocking tool, information later herein (with a photo). 
There is a second thrust washer.   The REAR thrust washer, similar to the front one, can come off its locating pegs.  It must be on its pegs, and not be rotatable by your fingers (check!) before you reinstall the flywheel.  Sometimes the pegs do not stick rearward very much.   You can use a very thin amount of a soft grease to 'stick' the rear thrust washer to the boss/pins.   Thrust washers are listed in parts catalogs by that name, and also by such names as stop discs, thrust discs, or stop rings.

When you remove your flywheel (for such as to replace a main seal, oil pump seal, etc.), it is CRITICAL that the crankshaft be BLOCKED from moving forward.  This blocking is usually done by some sort of makeshift tool that places some pressure against the alternator rotor center bolt.   This can be done in many ways, such as a piece of 2 x 4  lumber bungeed to the cylinders or exhaust pipes and with a screw to press against the rotor bolt. Very crude, that.   A small easy-to-make tool can be made of a piece of Allen wrench with a welded or brazed fender washer on one end, over-all about 3/4 inch long.  See next paragraph below. The outer cover holds it in place, the tool being made just a bit too long to allow the cover to fully bolt-up to the engine, and this gives a bit of pressure (do NOT overtighten the cover bolts!!).  The tool's Allen end simply fits into the existing alternator rotor bolt head.    I recommend you make one of these small tools the way I designed it.  You can also just use an 8 mm bolt, screwed into the rotor, leaving enough of the bolt forwards, so that the front cover will bear on it.

If you do NOT block the crankshaft, you run the REAL RISK of the crankshaft moving forward a small amount... it would need very little movement to have
the HIDDEN thrust washer move off the pegs.
   If that happens, the thrust washer will not align back on those pegs as you tighten the flywheel bolts (and you do not have to tighten very much to damage things), and you run the risk of MAJOR DAMAGE to the thrust washer....AND you may even damage OR RUIN the engine casting! 

With a thrust washer having fallen off its pegs, you will find that the crankshaft will essentially freeze up as you tighten those bolts.  You REALLY do NOT want this happening!!  You do NOT want to even get near the point of the crank freezing up.   If you forgot or did not know about blocking the crankshaft, and you want to know IF the crankshaft has moved, the sketch, well below, will give you the information.   If you have ruined a REAR thrust washer, that is NOT a disaster (assuming you did not injure the bosses area).   You just need another thrust washer of the SAME COLOR I.D.   Sizes are also listed in the literature.

If you have blocked the crankshaft before unfastening the flywheel bolts, you have nothing to worry about, regarding the crank moving and the forward thrust washer dropping!   You must be careful about the rear one coming off its pegs, when you re-install the flywheel.

The only way to see and get to (however slightly) and MAYBE get the forward thrust washer back in place if it has moved off the pegs, is either by removal of the right cylinder.....or disassembling the engine (totally!).    Do NOT think that you can simply tighten the flywheel bolts to see if the crank starts to seize up, that is, if engine rotation becomes more difficult.  By the time the crank gets to that point, you already have likely caused damage.  If you think you may have goofed, take the measurements!

If the forward thrust washer has already been destroyed/damaged, then disassembling the entire engine is your only option.  This is very serious business, with many additional ramifications not mentioned here.  So, heed my words, heed this article!!  BLOCK THE CRANK!!

YES, I am WELL AWARE that many have never had a problem from not blocking the crankshaft. PLEASE heed MY cautions, and DO block your crankshaft.


Snowbum's Tool to hold crankshaft from moving forward:

NOTE:   If you remove your flywheel for any reason, be sure to FIRST set the engine to OT, top dead center, Oberer Totpunkt, and be sure that OT is STILL in the timing window when replacing the flywheel.

Make the tool out of a piece of 6 mm Allen wrench material.   Weld a steel disc or 'fender washer', perhaps one of 1 inch in diameter, onto one end of the cut piece of allen wrench material.  The washer should be maybe 1/16" thick (not critical, no harm with thicker).   Make the length such that the Allen end fits FULLY into the alternator bolt, and the disc end presses against the inner surface of the timing chest cover.  Usually ~3/4 inch overall.  The length should be such that there can be some light pressure is applied by the cover when the cover is screwed back onto the engine LIGHTLY, but the cover can't quite fully be brought back to the engine surface. DO NOT over-tighten. 
     Weld the washer squarely to the straight piece of 6 mm Allen wrench.    The last time I made one of these, I made it to fit my 83-84 bikes, and the OVERALL length was 3/4".     You can also just use a 8 mm bolt in place of the rotor bolt, and not have to make this tool.  Some have just used a piece of allen wrench.  Carry it in the tool tray on the bike, but you are UNlikely to ever need it while touring.

NOTE:   If you remove your flywheel for any reason, be sure to FIRST set the engine to OT, top dead center, Oberer Totpunkt, and be sure that OT is STILL in the timing window when replacing the flywheel.

Below is a sketch of the flywheel and crankshaft of your Airhead.   Following this section is information on main seals, etc.

Dimension B is the depth of the flywheel (or clutch carrier, as it is called on 1981+ models) where the crankshaft boss fits into.    The sketch is simplified, and does not show how the rear thrust washer is retained, and other such minor details that are of no importance here.  

Another way of explaining things:   A must be greater than B by at least .05 mm.  If A is LESS than B, by, perhaps, 3 or 4 mm, then the crank has moved forward, and the thrust washer has slipped, and if one tries to bolt up the flywheel, serious damage will occur.    If the amount of forward movement is quite small, you may be able to move the crankshaft backwards with some relatively modest pressure at the alternator rotor. This might also be done by bolting up the flywheel to the crankshaft VERY LOOSELY and moving the flywheel rearward by hand pressure.   If you can move the crank by either method to the proper dimensions, A is larger than B, you have 'lucked-out', and you can tighten up the crank to torque specifications and the crankshaft will not be locked up. Be really careful!   


This original sketch was done by Tom Cutter who furnished it to me as I was too lazy to make
one.  That sketch was improved for clarity for me by Peter Holdcroft in July 2012.

Things look a little bit different for the clutch carrier models (1981+), but you will be able to see if there is a problem by taking the measurements.  I cannot emphasize enough how much I recommend you BLOCK THE CRANKSHAFT, by one of the methods outlined at the beginning of this article......thereby totally avoiding any problem...and you certainly will have no need to take these measurements. 

Flywheel bolt torques:
This is in reference to a BMW Service Information bulletin (we call them SI's), dated November 1991, #11-049-91, sub number 2495, & this can also be seen on the 12/92 fiche on page 3, G23.   In brief, it stated that while the flywheel bolts were previously at ~75 foot-pounds (100 Nm), they were now to be at 90 foot-pounds (125 Nm),... first you cleaned the threads,... and then the threads were to be OILED!  BMW specifically said that the bolt limits would NOT reach their limit of elasticity at that torque, and could be REUSED!    I personally get more than a bit nervous, at 90 foot pounds and oiled, so I will NOT tighten them that tight.  However, some do, and I have heard of no problems reported.  It is YOUR CHOICE.  NOTE that this is in regards to the 11 mm bolts....certainly not to the smaller /5 and early /6  10 mm bolts.  These early bike 10 mm bolts need replacement upon each use, which the 11 mm do not (unless overtorqued), and those 10 mm bolts in the /5 and early /6 are absolutely not be torqued to such high values.   There have been a lot of different specifications on flywheel bolts over the years.    There were also two lengths of 10 mm bolts used. 

 I use (clean and dry) torques of 42-45 foot-pounds on the 1973 and earlier engines; for the 1974 I use 52-55 ftlbs; and for 1975 and later models I use about 75 to 80 ftlbs.    Some aftermarket literature will show different flywheel bolt torques for different engine sizes for the same year.  DISREGARD such advice unless you KNOW what you are doing!    The big difference is in the size of the bolts, with the earlier 10 mm bolts as used on the /5 and into early /6, using substantially less torque.

For additional the section on flywheel bolts:

Crankshaft rear main seal:  

Repeated Note:   If you remove your flywheel for any reason, be sure to FIRST set the engine to OT, top dead center, Oberer Totpunkt, and be sure that OT is STILL in the timing window when replacing the flywheel; and that you have not rotated the crankshaft.

BE SURE you block the flywheel!!

Crankshaft main seals came in a number of styles over the years.   The very latest seal, of a Teflon-like material, is quite different in design from the early seals.   The latest type is 11-11-1-338-342.

***NOTE:   A type of geese-honking noise can sometimes be heard on an engine with the old style seals.  This noise comes from the slight vacuum created in the crankcase as the pistons go OUTWARDS, and the atmospheric pressure, being higher, in the clutch area, pushes air into the engine.  The biggest problem is NOT THE NOISE; but that clutch dust, which is abrasive, moves through that seal, slowly eating it away.  This is not good for the rear of the engine, let alone anyplace else the grit gets into.  It primarily happens on old worn seals, even if not yet leaking oil.  CHANGE THAT SEAL!

Early seals were very conventional looking, a white colored lipped rubber seal (there have been more than one type of lip and seal color) with a coiled spring backup.  For the /6 and later, BMW ADDED an O-ring in the flywheel bore.  For the /7 and later BMW added a metal cap ("Guide Ring"), and the O-ring is inside.  In 1981, BMW changed the design of the flywheel/clutch, for lighter weight  which gave faster engine acceleration and deceleration, unfortunately with more vibration, but also gave greatly reduced clutch hand lever pressure; the primary original purpose (Guessing).  The flywheel was now called a clutch carrier.  The earlier heavier flywheel had the main seal lip resting on the flywheel boss, so when the flywheel was inserted into the engine, the seal curled...well, sort of...ever so slightly inward.   For those earlier designs, I have recommended that the flywheel seal area be laboriously polished with ONLY crocus cloth (in kerosene).  Crocus cloth is a super-fine-grit polishing paper.  Absolutely no fingernail felt irregularities are allowed in the flywheel sealing area...although discoloration is normal.  All seals before the latest Teflon type, 11-11-1-338-342, were installed slightly different or controlled depths to avoid old rubbed areas. 

Main Seals must be installed squarely.   Main Seals often fit very tightly, and you might have problems trying to get them into their cavity.  It REALLY DOES help to warm the engine case up, considerably, in the main seal area; and this can take quite awhile.  Lightly oil the seal just before you install it.  Install it must be installed straight and square.

The cap, or "guide ring", used on the 1981+ models (the clutch carrier fits to it, the guide ring is over the crankshaft) and has a center lug to enable it to be pulled rearward by a factory tool.  To replace a main seal on a 1981 and later, you have to remove the guide ring first.  You can improvise.  You can use a flat punch to rotate the ring until some of each crankshaft hole is covered, then pry to the rear....use a small screwdriver or similar, pry a bit on each hole/guide ring.   Be careful, not to damage the guide ring nor the threads.  Once the guide ring is out, you can remove the main seal.   The Guide Ring can deteriorate (hard coating).  If the surface appears to be deteriorating, that surface could have teeny imperfections that would eventually tear-up a new main seal.  Replace the Guide Ring if it has so deteriorated

With the guide ring removed, you then install the new-style main seal.  The guide ring (with a new O-ring!) is then moved into the main seal, using the carrier bolts.  When using the bolts for that, you may need to use spacers under the bolt heads....see the guide ring installation photos, later here, showing the bolts with some sort of junk-box provided spacers under them, to allow the bolt heads to be turned properly.   As the guide ring is installed, it makes the "Teflon-like" seal working part move forward.  That helps the seal maintain oil integrity as crankcase pressures increase during engine operation. 

Leaks that seem to be the rear crankshaft seal could actually be that rubber O-ring.   However, determining which is which may not be so simple, so most just replace both mainseal and O-ring.

****Main seals are usually installed using the special factory tool, but if you are careful, you can do this with a prepared block of wood (or Ed Korn's tool).  Install the seal absolutely straight and square.  While I think ONLY the latest seals type should be used, which is installed to full depth, if you have an older style seal you are installing, you would install at the same original depth...except that early flywheels with a big radius are best installed not quite fully...maybe a mm will be proud of the surface.   See notes below.

Here is a link to a pdf file on this website that has the factory information on the new style seals:

MORE on the new style seal:
The latest 11-11-1-338-342 seal is a "Teflon-like" (PTFE) seal.    NOTE that it is designed so if you install it squarely, you can install it fully, without bothering about setting the depth.
There area two types of flywheel (or clutch carriers) in use.  If the front end has a small radius, then the seal is installed to full depth.  If there is a taper, as on early flywheels, then the seal is rearward a small amount, about 1 or 1-1/2 mm.  Oak uses rear ring gear shims for that, installing the shims, then the seal.  I don't....because I don't have any stock of them.

Hints: The latest version needs no oil soaking; but it is best to install it oiled or lightly greased a bit for ease of installation. Using a very fine sandpaper, sand the aluminum entrance edge to the bore in the case to allow the seal to press-in easily.  Oil slightly (or lightly grease), the bore area of the engine case that the seal fits into and the seal outer too.  If you heat the engine case around the prepared seal bore area, then add a tad of grease or oil, the seal will press-in easier.

While you do NOT have to do this, I do: soak the new seal and installation tool in 150F +-   engine oil for a few minutes....the warmth helps prepare the seal, perhaps softening it.  

If you have an earlier new seal (are there any still around?...I suggest you toss it and use the new seal.

If you fail to oil or grease the new seal during assembly, it may squeak for a short while after engine start, until oil works its way to the seal.    Press the new seal in squarely, using a flat plate seal installation tool, or fashion something.   Install the flywheel (carrier) with a bit of oil on the nose.  

There area two types of flywheel (or clutch carriers) in use.  If the front end has a small radius, then the seal is installed to full depth.  If there is a taper, as on early flywheels, then the seal is rearward a small amount, about 1 or 1-1/2 mm.  Oak uses rear ring gear shims for that, installing the shims, then the seal. 

****Oak did an article on main seal installation in the MAY 2004 issue of AIRMAIL (see page 17-18)...where he discusses this in some depth, in response to a question posed by someone.  ****

Be sure the 5 holes in the guide ring are exactly aligned with the crank holes, as you do this job.  

If you use one of the plates-type of installation tools, you need not tighten the bolts very much.

Some recommend installing the flywheel when it has been heated fairly hot.  When you align a 'flywheel' to the crankshaft, install by eyeball first.  YOU SHOULD HAVE previously set the pistons fully outward; and now when you reinstall the flywheel, its OT mark is in the timing window, and you've double checked OTC on the pistons....... then insert the bolts lightly finger tightened, and then find the centering point of the assembly, by moving the flywheel CW and CCW, back and forth on the bolts...there will usually be a very slight amount of play.  Then tighten to only a few foot-pounds, evenly, cross-pattern as best you can.  If the flywheel was not heated, tighten fully to specifications at this point, in a cross-pattern.  If the flywheel WAS heated, wait until it has cooled, then tighten fully to specifications. Mind the torque.  As noted previously, the early 10mm bolts must be new.  The 11 mm ones are reusable, unless damaged from over-torquing.

A tool can be fashioned to lock the flywheel/carrier, while the bolts are torqued.  Such tools are shown in photos in such as Clymer's and Haynes manuals, BMW literature, ETC.  The original BMW tool may even be available, but the tool is quite simple.   I recommend you do not lock the flywheel/carrier by using the starter teeth.

Main Seal installation tools (if you decide to use them):

The original BMW main seal installation tool was #880.
There is an article on making a fancy, nice, main seal tool that works fine with the later seals.  The article is here:

In the photo below, note that the BMW stepped plate can be used upside down for flush seals, or with the step to the inside for installing to slightly forward of flush.   The Ed Korn type tool shown uses setscrews to adjust the depth...and the tool seller provides instructions with the tool.
There area two types of flywheel (or clutch carriers) in use.  If the front end has a small radius, then the seal is installed to full depth.  If there is a taper, as on early flywheels, then the seal is rearward a small amount, about 1 or 1-1/2 mm.  Oak uses rear ring gear shims for that, installing the shims, then the seal.  I don't....because I don't have any stock of them.

Thanks to Al Patton for supplying the original photos of a later type Airhead (type with Guide Ring), which I have modified and placed below.

NOTE the thrust washer and pegs!
That are 5 bolt holes in the crankshaft you see here, and notice that they are symmetrical...that is why you MUST
align the flywheel/carrier for OT mark with pistons fully outwards!

Notice the spacers used by Al Patton here...otherwise the bolts would not turn at the hub area.

Notice that the holes all are lined-up

The 10 mm hex bolts at the oil pump cover
are the later types.

NO need to tighten much!
When installing the flywheel, mind the information early in this article on bolts & their torques! If flywheel bolts loosen, or come out or are sheared off, considerable damage to the threaded holes can occur.   This most often was seen on the old /5 bikes, with the smaller threaded bolts, with someone forgetting they were on a German bike, and shifting the wrong way, from, let us say, 2nd, with lots of rpm, down to first.  That sheared the bolts.  I've fixed a few of those!! If you are removing the clutch (obviously needed if removing the flywheel), MARK the position of the major parts to each other, except the clutch diaphragm spring.
NOTE:   If you remove your flywheel for any reason, be sure to FIRST set the engine to OT, top dead center, Oberer Totpunkt, and be sure that OT is STILL in the timing window when replacing the flywheel; and that the pistons still really are fully outwards. Suppose the engine rotated some, or you forgot to mark things...or, the flywheel or clutch carrier was mis-positioned by a previous owner.  How do you find the proper flywheel position?  The safest method is probably this:

1. Remove the valve cover on the left cylinder
    & remove left and right cylinder spark
    plugs so the engine is easy to rotate.
2. Place the flywheel into any bolt-hole
    positioning, lightly putting in a few bolts,
    but fully home. Remove the crankshaft
    stop tool only after the flywheel is in place
    & those bolts lightly tightened.
3. Rotate the flywheel slowly in the NORMAL
    direction, which is CLOCKWISE as you
    face the flywheel from the rear.  Watch the
    left INTAKE valve.  After the INTAKE valve
    closes, continue to rotate in small amounts,
    shining a flashlight into the spark plug hole.
    You will see the piston come fully out, then
    reverse. Both pushrods, piston fully
    outwards, should be easy to rotate by
    your fingertips, & a double check is that
    both valves are fully closed.
4. Rotate the flywheel back & forth, CW &
    CCW, small amounts until piston is fully
    outwards, eyeballing it is good enough!
5. Some might use a round tip metal rod for
    'feeling' the piston. Do NOT bugger-up the
     spark plug hole edges. Do NOT use a
     pencil, it could break.
6. With the piston now fully outward, if the OT
    mark is not someplace IN the timing
    then remove the flywheel & position it so
    OT is in the window.
7. You can skip removing the valve cover in
    step 1, and then skip step 3, if you feel OK
    about 'feeling' for the piston coming
    outwards. It does not matter which stroke
    you are on, just that the piston is fully
    outwards relatively closely.
If the flywheel has a groove, and it will if it is 10/1975 or later, it needs an o-ring there.
It was 11-22-1-337-099, now is -093.  A long time ago the number was 11-22-1-263-798.
The O-ring is called a Seal Ring by BMW.  It is 59 mm x 3 mm.


Oil pump and oil pump cover:

The oil pump cover O-ring should be replaced any time the flywheel is removed.   Early oil pump covers had Phillips screws, which often are a problem to remove (use of the special impact wrench listed in my article is highly suggested!).   Early pump covers had tapered screw holes to accommodate the flat head Phillips screws.   Early pump covers did not seal as well either, and the later type covers ALSO fix that potential problem, with groove depth and later thicker O-ring. If you have a Phillips type cover, I highly recommend you install the later pump cover, with the later hex-head bolts.  When installing the pump cover with its new O-ring grease the O-ring, or otherwise be very careful that the O-ring stays in place during the installation/tightening process.  I use Loctite BLUE on the threads; and I am careful to tighten the 4 bolts evenly, in a cross-pattern, a bit at a time, until tight....88 INCH-pounds (that is only 7.3 footpounds).

The oil pump inner rotor INNER EDGE is chamfered, in case you remove it and wonder what direction to replace it in.  Another way is that the punch marks go to the rear. You do not have to line up the punch marks.  Oil pump clearances are easily measured with common feeler gauges and a machinist's or other, straight edge rule, on edge.   Here are some general specifications:
Rotor 2.22"  +0-.0009"
Housing 2.23"  +.0017" -0
Rotor end clearance .004-.007"
Rotor thickness .54" -.0066+.0013"
Rotor to housing face .001" to .0023"
Rotor to rotor clearance .0046" to .0117"

NOTE:   Original oil pump O-ring was black 11-41-1-250-274, 0.079" thick.  That part was discontinued a long time ago in favor of a red O-ring that is slightly thicker, at 0.084", part 11-41-1-335-895.  SOME parts lists and on-line fiche, will show it as 11-41-1-335-896.


Things can get rather complicated in setting up a lower end, particularly if it is a NEW crankshaft.  BMW has specifications for the matching of the crank color code; main bearing bushings, and the bearing cap (front main bearing holder).  Generally, it is a matter of matching color codes on these things...but the Factory Manual has the various specifications. 

MOST of you will never have a crankshaft out, let alone be changing one.  

A few of you may have the crank out for re-shimming...and I have the information later in this article on that.  BMW lower ends are very long-lived, providing they get clean oil all the time.

A very grabby clutch, vibration, hard shifting, and idle rpm change with clutch lever use, usually means it is time for shimming the crankshaft.  Details are in this article somewhat further down this page.


Front main bearing and its cap/holder/carrier:

Pay attention to the information in the books about properly positioning things, and the oil holes being vertical and about the drilling needed on the two holes through the bearing...0.124"...right through the existing front bearing carrier, and then the bearing area.  A new locating pin hole....taper hole, partial at 0.156", and full at 0.148"....there is a special ream...etc.   All this is being mentioned for you, & not put in exacting detail, to be extra cautious in not just willy-nilly changing things.  Things are not always as you may think they are....ask questions on the Airheads LIST!!

To remove the front holder you need to use a puller, either BMW's, or a steering wheel type for a car.  Use a good hardened bolt with a countersunk depression you put in it on a lathe, in the crank nose, for protection.  YOU MUST HEAT THE AREA QUITE HOT, WITH A LARGE FLAME TORCH.

For the nerdy:   There is a bushing (main bearing) in the main bearing cap.  Heat the cap to sizzle and press out the bushing. Reheat to install new bushing.  Be sure to line up the oil hole and have the joint properly offset from vertical (the hole).  I can supply a photo of this.  Once the bushing is installed, you have to drill two oiling holes, and ream properly.  The bearing cap holes are already 3.2 mm.  Details as in the factory manual must be followed.   You will be installing a retaining pin, a taper fit, and then locking it in place with punch marks.  It prevents the bushing from rotating, and cutting off the oil supply.


Grinding crankshafts:

Do NOT re-grind crankshafts, even though undersize bearings are available from BMW, unless you are prepared to re-heat-treat the area that was ground, and to radius the sharp corners, etc.  This is VERY tricky to do.  BMW offered the published undersize bearings because of RARE production use of undersized crank journals...but there is another reason, somewhat allied, so keep reading.   NOTE that the nitride type hardening of the stock crankshaft is not very deep!  Due to the weights on the crank being in the way, I don't think you will be able to grind a crankshaft anyplace, let alone re-nitride treat it.


Crankshaft end play, spacers, ETC: 
Crankshaft end play is set via two thrust washers at the rear end of the crankshaft.

It is NOT a difficult job to set end play.

Fairly rarely and after huge mileages usually, one sees an Airhead that has two or more of the following symptoms:   Shifts hard, (BUT isn't input shaft play or lack of splines lubricant or bad clutch); most probably has a lurching, grabby clutch action; idle rpm is unstable and varies a fair amount with clutch pull-in; engine vibration.  

If you have an airhead with those symptoms, you may want to check the end-float (end play) of the crankshaft. This is a serious subject.  You are advised to see an expert, or to get the BMW official information, but here are some things that may clear things up a bit.  You will have some color(s) of thrust washers on both sides of the engine housing.  It is these that set the end-float of the crankshaft.   SOME BMW Manuals have the sizes of these WRONG (in converting the mm to inches).  A bit of work is involved in setting up a crank from scratch, so if your existing crank has only excessive end play, you may want to just change the thickness of the OUTSIDE (rearward) spacer.  BMW has specifications on end play, or end-float as they call it, and you need to understand that it varies if oily or dry, and BMW does not tell you about that.  The end-float specification is 0.08 to 0.15 mm (which is 0.003" to 0.006").  This is for DRY.  If oily, the minimum is 0.15mm (0.006").    If you have removed the crankshaft, and are installing it, you may want to lower your labor by installing the thinner RED spacer inside.  Thusly you likely will not have to remove the crank again, just select the appropriate rearward spacer.  Note that BMW has a limit for wear, and it is 0.20 mm (0.008").

Here are the real values of the thrust spacers:
RED:   2.483 mm to 2.530 mm (0.0978" to 0.0996").
BLUE:  2.530 mm to 2.578 mm (0.0996" to 0.1015").
GREEN:  2.578 mm to 2.626 mm (0.1015" to 0.1034").
YELLOW:  2.626 mm to 2.673 mm (0.1034" to 0.1052").

NOTE:  A grabby clutch can ALSO come about from clutch parts AND from excessive transmission input shaft end-play.

Crankshaft REAR bearing (a bushing type):
The case is heated to sizzle in the area, and the bush pressed out.  The case is reheated to install the new bush.  The bushes are available in oversizes to match your existing crankshaft, if it came undersized. YOU CAN NOT likely have your crank ground properly if the bearing area is bad. MAYBE.  There is a oil groove and oil HOLE in the new bushing.  As you look from the rear of the case, with the pan surface facing you, the joint of the bushing is at the top right, and the oil hole is at the top.  For the nerdy, the bush joint is 26 to the right of vertical.

Changing the front main bearing?...and confused about its holder/carrier??:  Pay attention to the information in the BMW factory literature about properly positioning things, and the oil holes being vertical and about the drilling needed on the two holes through the bearing...0.124"...right through the existing front bearing carrier, and then the bearing area.  A new locating pin hole....taper hole, partial at 0.156", and full at 0.148"....there is a special ream...etc.   all this is being mentioned for you, and not put in exacting detail.... to be extra cautious in not just willy-nilly changing things.


Regarding rod bearings and caps and bolts:

I do NOT reuse the rod bolts!.....
NOTE that the conrod bolt is a special type, although it looks like a Torx.   You can get the tool from NAPA as part 2305, which is the same as K-D tools part 2305.   Be sure to oil these parts rather well as you assemble them and also put the tab into the cap slot; and the rod on correctly....that is, the located pins will be facing forward! Tighten the rod bolts slowly, don't use too much torque at first, so you can check for smooth operation of the rod on the journal....BEFORE you tighten to the final value of 35-38 footpounds; NOTE that the R80GS, R80R, R100GS, and R100R are to have the rod bolts tightened in stages, by degrees.   Initial preload on them is 15 footpounds, then you go to 40-45 degrees more.

Vibration, noises, etc.:
There have been instances, in the seventies, and suspicions by me of even in the eighties in some R80 engines, possibly others, that some noisy engines, or engines with vibrations that have not shown up as anything else, are caused by out-of-tolerance crankshaft bearings. I am not speaking here of the end spacers at the rear of the crankshaft that set end-play of the crankshaft.  Rather, I am speaking of the bearing shells & crankshaft journals.
This is a complicated subject, & reference to a very technical SI is needed, but basically, the main journals should have a clearance, measured by plastigauge or other means, of 0.0014" to 0.0026".  If the clearance is over 0.0026", BMW offers a mid-oversize bearing shell, number 11-11-1-265-437.   This is the green one.  There are quite a few other such shells, of various dimensions, you would need the SI, & a fiche or on-line listing(s), & some knowledge.  To measure the front main bearing cap internal diameter, the crankshaft must be removed, but the cap bolted in place!

Timing chest seals:

There is sometimes confusion over the alternator and camshaft seals used in the the inner cover.  All models use 11-14-1-255-011 alternator seals, probably 28 x 47 x 7 mm...have not measured to confirm that size.
The camshaft seal up to models built in 9/1975 was 11-14-1-261-193.   It must not be use in later models, or there will be leaks. The later cam seal is 11-14-1-262-977, is 20 x 32 x 7 mm.
See the article on doing a 'timing chain' job on this website.


For the curious, the chain size is 3/8 x 7/32, both SIMPLEX, and DUPLEX.

Crankshaft bearing:   For many years, this was number 07-11-9-981-722, and is 35 x 62 x 9 mm. The bearing number has been changed to  07-11-1-468-882.   It is a common bearing, but you must get the correct GRADE. The bearing is   FAG16007-C3



02/04/2008:    incorporate all previous revisions; expand and also add information from "being-eliminated"
                     article engineinternals.htm; clarify details on main seal installation.
02/11/2008:   Photos of rear seal installation.  Fix typo on which sub-section of article 60.  Edit entire
                     article A/R, for clarity and emphasis.
04/24/2009:   Minor changes to text in one photo.  Clarify the 90 foot-pounds that are only on the 1981+
05/10/2009:   Remove most of the emphasis and base colors, as experiment.
01/15/2010:   Clean up article for better clarity, less verboseness.
08/08/2010:   Add information on the crank tool from my TOOLS article
05/31/2011:   Cleanup
08/01/2011:   Add Addendum area with note on the REAR thrust washer problem.
06/18/2012:   Add minor commentary on the O-ring.
07/29/2012:   Flywheel warning sketch replaced by improved clarity version. Clean up article a bit.
09/04/2012:   Add "suppose the engine has rotated some...." section.   Add QR code; change Google ad
                     display, add language button
12/12/2012:   Insert old crank.htm article and begin to completely revise
05/01/2013:   Oil pump O-ring part numbers and description changed.
08/03/2014:   improve the description of the crankshaft and bearings tolerances description and why.
04/06/2015:   Additional information on the O-ring, and history.

Copyright, 2014, R. Fleischer


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