Flywheel, removal warning, main seal, oil pump cover, oil pump

FLYWHEEL REMOVAL WARNING!!!
Flywheel Re-installation, MAIN SEAL Installation, oil pump and oil pump cover, ETC

This CAN BE CRITICAL, so Flywheel Removal is the first item in this article:

When you remove your flywheel for such as to replace a main 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 lumber such as a 2 x 4, 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. 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. The tool's Allen end simply fits into the existing alternator rotor bolt head. A picture of this sort of small tool is on this website, at tools.htm as item #8 of that article. If you do NOT block the crankshaft, you run the risk of the crankshaft moving forward a small amount... probably it could possibly move a bit under 1/4", and the HIDDEN thrust washer COULD move off its pegs. If that happens, the washer will not align back on those pegs as you tighten the flywheel bolts, and you run the risk of MAJOR DAMAGE to the thrust washer....even the engine casting. You will find that the crankshaft will essentially nearly freeze up as you tighten those bolts. You REALLY do NOT want this happening. If you forgot or did not know about blocking the crankshaft, and you want to know IF the crankshaft has moved, Tom Cutter's sketch, below, will give you the information. The dimensions need to be as shown, in order to know that the crankshaft has not moved. The only way to see and get (however slightly) onto the hidden thrust washer, if it has moved off the pegs, is via removal of the right cylinder.....or disassembling the engine! Do NOT think that you can simply tighten the flywheel bolts and 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 caused damage to pins and thrust washer.

If the thrust washer has already been destroyed/damaged, then disassembling the engine is your only option. This means a near total tear-down, and includes pulling the front bearing and removing the right piston, enabling you to move the crankshaft forward in order to replace the thrust washer. This is very serious business, with many additional ramifications not mentioned here. So, heed my words, heed this article!! BLOCK THE CRANK!!

Below is a sketch of the flywheel and crankshaft of your airhead, sketch courtesy of Tom Cutter, with additional notes by me. 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 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 about all this sort of thing!
_{Another
HINT!.....

     BMW Service Information
bulletin (we call them SI's), November 1991, #11-049-91, sub number 2495, and this can also be seen on the 12/92 fiche on
page 3, G23::    Basically, 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), cleaned
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 will NOT tighten them that tight.
Makes me very nervous! However, some do, and I have
heard of no problems reported. It is YOUR CHOICE.
NOTE also that this is in regards to the 11 mm bolts, and applies
to 1981+ models....certainly not
the smaller /5 and early /6 10 mm bolts; which need replacement upon each
use, which the 11 mm do not, 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 two lengths of 10 mm bolts used. I
use, clean and dry, torques of 42-45 foot-pounds on the 1973 and earlier
engines; and for the 1974 I use 52-55 ftlbs; and 1975 and later up to the 1981
models, I use about 75 to 80 ftlbs. I use about 80 ftlbs, clean and dry
threads, on 1981+.}

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. for the nerdy here...see: http://www.elring.de/tsi/TSI_03_04_e.pdf

Early seals were very conventional looking, a lipped rubber seal (more than one type of lip and seal color) with a coiled spring backup. The 1980 and earlier models had just the conventional seal. In 1981, BMW changed the design of the flywheel/clutch, for lighter weight (faster engine acceleration and deceleration, unfortunately with more vibration). The clutch was radically changed too.... to eliminate weight, and greatly reduce hand lever pressure. The flywheel was now called a clutch carrier. The earlier 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 always recommended that the flywheel seal area be laboriously polished with ONLY crocus cloth (in kerosene). Absolutely no fingernail felt irregularities are allowed in the flywheel sealing area...although discoloration is normal. Seals were installed sometimes to very slightly different depths to avoid old rubbed areas.

The "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. 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.

To replace a main seal on a 1981 and later, you have to remove the guide ring first. You then install the seal. The guide ring (with a new O-ring!) is then moved into the seal, using the carrier bolts (probably with some washers/spacers). 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.

***When using the bolts for that, you may need to use spacers under the bolt heads....see the guide ring installation photo, showing the bolts with some sort of junk-box provided spacers under them, to allow the bolt heads to be turned properly.

Main seals are installed using the special factory tool, but if you are careful, you can do this with a block of wood (or Ed Korn's tool). Install the seal absolutely straight and square. Install at the same 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.

MORE on that new style seal:
The latest seal is a "Teflon-like" (PTFE) seal. The latest version, again see: http://www.elring.de/tsi/TSI_03_04_e.pdf, is installed DRY. DO oil, slightly, the bore area of the engine case that the seal fits into. If you have an earlier seal, soak the new seal (and tool!) in 150°F +- engine oil for a few minutes....the temperature helps the job of preparing the seal, perhaps softening it, perhaps not. If you fail to oil or grease the working part 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.

****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. By the way: 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 (mind the OT mark and be at OTC on the pistons!!), then insert the bolts lightly, 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 slight amount of play. Then tighten to only a few foot-pounds. When it has cooled, tighten fully to specifications. Mind the torque. There are two types of threads (to 1974 10 mm and then later 11 mm). The 10 mm ones need to be replaced every time, not so the later ones, unless they had been seriously overtorqued.

A tool can be fashioned to lock the flywheel/carrier, whilst 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.

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 on the http://www.airheads.org website, and it is also here: http://www.gunsmoke.com/motorcycling/r100gs/mainseal_driver/index.html

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 Ed 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.

That is the 5 bolt holes in the crankshaft you see, above, and notice that they are symmetrical...that is why you MUST align the flywheel/carrier for OT mark with pistons TDC!	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 bottom area are the later types at the oil pump cover.
NO need to tighten much!

_{Another
HINT!.....


BMW Service Information
bulletin (we call them SI's), November 1991, #11-049-91, sub number 2495, and this can also be seen on the 12/92 fiche on
page 3, G23::    Basically, 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), cleaned
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 will NOT tighten them that tight.
Makes me very nervous! However, some do, and I have
heard of no problems reported. It is YOUR CHOICE.
NOTE also that this is in regards to the 11 mm bolts, and applies
to 1981+ models....certainly not
the smaller /5 and early /6 10 mm bolts; which need replacement upon each
use, which the 11 mm do not, 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 two lengths of 10 mm bolts used. I
use, clean and dry, torques of 42-45 foot-pounds on the 1973 and earlier
engines; and for the 1974 I use 52-55 ftlbs; and 1975 and later I
have used about 75 to 80 ftlbs.    Some
knowledgeable 'Wrenches' are using 90 ftlbs OILED, with no
problems.   Whilst engines I have installed
flywheels/carriers on have not loosened, to my knowledge anyway;
in the future I will probably go to 75-80 ftlbs OILED, on the 11
mm bolts.}

If flywheel bolts loosen, or come out or are sheared off, considerable damage to the threaded holes in the flywheel can occur. This most often was seen on the old /5 bikes, with the small 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!!

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 tools.htm article is highly suggested!). You can install the later pump cover, with the later bolts. When installing the pump cover with its new O-ring, be sure to 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. 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"

Rev:

02/04/2008: incorporate all previous revisions; expand and also add information from "being-eliminated" article engineinternals.htm; clarify details on mainseal 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+ models.
05/10/2009: Remove most of the emphasis and base colors, as experiment