Ignition Timing and Automatic Advance Unit, Single Spark Plug Airheads.  Installing and adjusting points.    Automatic timing units for the dual plugged airheads as well as the single spark plug airheads, and some information on various coils, etc.
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ignitionsingleplug.htm-29

This is FIRST, so please pay attention!   Everything on this long page is only PART of what you really need to know about the airhead ignition system, and all its components.  PLEASE be SURE to read not only this article #29, but to read #28, 30, 31, 32!!  SOME things in some of those articles ARE pertinent to the points models, setting, adjusting, and many other details!

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Section I....Dealing with POINTS removal, replacement, adjustment, maintenance.  NOTE, be sure to read ALL of this long article, not just this section!...as there ARE other pertinent notes!::::

It is extremely common to hear about a poor running engine, and often hard-starting engine.....the cause being nearly completely closed-up points.    

When I install brand-new points, I set them a tad wide, about 0.019" for all models, and I am VERY careful to lubricate (sparingly!!) the cam and the felt.  Since I have to remove the ATU (on models through 1978) to replace the points, I also lube the shaft, and inspect the ATU.  If you do NOT lubricate the cam, the points rubbing block will wear rapidly, closing the points.  On the 1979-1980 models, the points are in the canister, and things are a bit different, but you still must have a faint trace of lubricant on the points cam......the ATU is not 'available' for lubrication, it is buried at the bottom of that canister.  

I've even heard those rubbing blocks (especially models up through 1978) make squeaking noises.  Bosch has several lubricants for use at the points cam, and at the shaft.  I prefer to use the original specified lubricants, but I WILL use almost anything in a field repair....ou can use any good high temperature grease.....even something like BMW #10 red grease will help.   I still have the same tubes of my original Bosch grease, that I probably purchased 35 or more years ago...and I used those tubes a lot!  FYI, the Bosch numbers are:   Ft 1 v4   for the felt; Ft 1 v22 (or 26) for the ATU

Earlier than 1979 points ignitions had felts, and the felt and cam required lubrication, and since the automatic advance unit was at the cam tip (not buried as in the canisters), the automatic advance unit required cleaning and lubrication now and then, with two types of greases used, one for the rubbing block, one for the area between automatic advance and cam.

Caution!!!....The nut on the camshaft tip (through 1978) must NOT be overtightened!  I do it with a short 4 inch wrench, and by feel.  I would guess that I don't use more than 4 footpounds (at the most).  Specifications are 4.3-5.1, and I don't use that much.     A waverly spring washer belongs under the nut.

When setting the timing, the points gap MUST be set FIRST.   Rotate the points plate CCW to advance the timing.  Points wear is almost entirely that of the rubbing block, and the points themselves.  Do NOT ever 'file' the points, unless it is more or less an emergency or field problem;....the points have a rather thin layer of something like tungsten (?) on them, and the filing
can remove that hard layer.    Don't open the points quite wide with your fingers when installing, etc....you can take some of the tempering spring action out of the points leaf spring....and then the points may 'bounce' at high rpm, causing misfiring of the ignition.

If the capacitor fails (not all that common, actually), the ignition can either quit, or the points starting burning up at a fast rate. Points will last about 12,000 to 25,000 miles.   Most will last 15,000, but you DO have to maintain a slight lubrication on the cam.  Contrary to my own above advice, on a few of my touring airheads that had points, what I actually did was to, yes, very LIGHTLY, file the points with a very thin diamond coated blade (300 grit) every 5000 miles when I set the valves ( I did the valves first, before the points, so I did not have to wait for the engine to cool after setting timing).  I check the cam lube, check the gap, checked the timing at high rpm....rode the bike, and synch'd the carbs.....this was standard at every 5000 mile interval.  I don't really recommend filing points.    I have gotten some very big mileages off a set, but don't recommend trying for that.  

You can eliminate wear of the points themselves (you still have to replace them eventually, for rubbing block and other wear, but they will last a LONG time, if you keep the cam lubed) by using some sort of points amplifier.   Keep the capacitor in its normal place, and you can, if the amplifier fails, convert to the stock system in a FEW minutes!  Dyna still makes points amplifiers, and are probably others.   There are full electronic ignitions available too, but if one fails on a tour, you are less likely to fix it as easily as the points amplifier equipped type.

If you use a points amplifier, it is even more important than with the stock setup to never let the points get dirty/oily/greasy; as the current through the points is vastly lessened with the amplifier.    When stock, that larger current helped keep the points in usable electrical contact when closed.....although allowing pits and valleys and burning to occur.

Prompted by an inquiry, I am adding this:

NOTE, in case you have a 1979+ bike::::   The canister was used with POINTS in 1979 and 1980.   The 1979 and 1980 canisters with points did NOT have a felt pad to help keep the points cam lubricated, hence, if the lubrication on the cam dries out, the rubbing block and the cam, together, can make a very loud chirping noise.  In that case, remove the outer lid (2 screws) and lubricate the cam and sides of rubbing block....all sparingly....with a high temperature grease.   Put one drop of a decent oil on the outrigger bearing.  NOTE that the points can NOT be adjusted withOUT the outrigger bearing in place.

Section II:  Everything else::

BMW modified the automatic ignition advance unit around the end of 1972 when not far into the early production of the /5 airheads.  Changes were made now and then in the early years, in that mechanical advance unit; and, in the flywheel markings. The stamped part number on your automatic advance is a Bosch number. Not only was the cam profile of that automatic advance unit that bumps the points changed from 110° to 78° dwell with a sharper shape, but the springs were changed, and not all this at the same time. So, you have the DWELL changed, the RATE of advance, and the RPM at which the advance stopped advancing. Going along with this was a change in the flywheel markings.  

What follows, before I get into anything else, is the total technical story on the automatic advance units used on the NON-canister bikes (prior to 1979).   Keep in mind that it is possible that someone has changed the springs on your automatic advance, or even otherwise modified it.

In 1972 and into 1973, BMW made changes to the automatic advance (centrifugal advance unit).  This was done to the R50/5 after chassis 2901787; R60/5 after chassis 2932689; R75/5 after chassis 2973307.  The changes shown below described as 'fully suppressed'  generally mean the Authorities (police) models.

Prior mechanism:   Bosch 023 202 005    BMW 12-11-1-351-571   15°30'  timing.  Note that the early mechanisms had a 110° dwell.

Updated mechanism:   Bosch 023 202 007   BMW 12-11-1-353-639     12°30' timing.  NOTE that some were 110° dwell, some were 78° dwell, same part number.  The 78° also were more abrupt.

Updated mechanism, but with the breaker plate fully electrically noise suppressed, complete assembly, Bosch 023 202 008; BMW 12-11-1-354-404.   12°30' timing.

The automatic advance unit is INDEXED by the D shaped flat on the nose of the camshaft, where it fits precisely the same D shape on the automatic advance.   

BMW changed the relationship between the camshaft and the timing mechanism function....that is, a change in the timing of the automatic advance cam in relationship to the camshaft.  

 BMW changed the changed the flywheel markings.  ONE flywheel MARKING was repositioned.   With a timing change of 3° at the cam, the flywheel change is twice that, or 6°.  The NEW timing point is thus 6° BEFORE the original marking, as seen in the direction of the moving flywheel.  That was 12.5 mm on the flywheel, in the direction OF THE TDC (OT) MARK.  NOTE that the STATIC ignition timing (also called idle timing, the S mark) was NOT changed, it remained at 9° BTDC.   Obviously, OT, top dead center marking, was not (and could not be) changed.    Think about the differences of no-change at S, and a 6° change at the maximum advance point.    Keep in mind that the timing change was, in effect, that of a mechanical place of points opening, and a flywheel marking change.  

If you use a dwell meter on the BMW points, you probably do not have a 2 cylinder dwell position.  Thus, if you have a 78° timing cam, and set the dwell meter on the 4 cylinder 4 stroke position, the dwell meter should read 39°.  In the same manner, the 110° timing cam will read 55°.

The reason for the change from 110° to 78° was that the Police models, with their heat retaining metal shielding around the ignition coils, were having coil failures.  78° is MORE THAN ENOUGH dwell for full coil saturation, at airhead engine speeds.   Racers using extreme rpm might get a wee bit more out of the early 110° cam, but the points don't like that high an rpm, and racers are likely to be using other ignition means, such as electronic triggering from Hall element or light sensitive devices.

CONFUSING THE ISSUE FURTHER, IS THE FOLLOWING:

Only 2 or 3 months later than BMW's phasing in of the FIRST automatic advance change, BMW was finding a lot of pinging (pinking), in countries where the gasoline had a relatively low octane.  BMW again changed the automatic advance, now so that the prior maximum advance which was obtained at about 2200 rpm, was now to be 3000 rpm.  The previous 'new' mechanism, 12-11-1-353-639 retained that part number.  BUT the Bosch number on the automatic advance changed, and the ONLY change was the springs.   Do see later, below, Special NOTE #1:

0232002007 Bosch, BMW 12-11-1-353-639, was now 0232002010

The fully suppressed assembly was 0232002008, was now 0232002011

The early springs were BMW 12-11-1-356-142, the newer, stiffer springs, were 12-11-1-356-546.

NOTE that Performance bikes, with good gas, will perform better with the early springs giving faster advance and 2000 rpm for full advance....and one might consider using the 110° dwell unit.

NOTE that an even later automatic advance unit was made, carrying the Bosch number ending in -012, and was used on the late /6 and /7 to 1978, still with 78° Dwell.  

Special NOTE #1: Units ending in Bosch numbers 007-012 had advance limited to 34° BTDC.  Only the 005 unit had 39° BTDC.    The early advance looks the same but the holes in the cross plate allow the advance to swing a bit more open.   Those hotting-up their bikes should know about this.  

In 1979 BMW went to the canister system, and the 1979 and 1980 were 120° dwell, using POINTS. With the late coils, and the canister points ignition, the ignition was quite good, although faster advance on hotted bikes on good gasoline's give improved performance.

BTW:  the Electronic Ignition has 104° dwell.

Special NOTE #2:  When BMW made the changes to the timing, BMW suggested repainting the timing marks.  This was because if one put a 007 unit into a 005 bike, the F mark would not swing far enough.  If one timed at the S, it was OK...but you would have to ignore the F mark....but, S is not the REAL place to time a bike, the F mark is THE important one, leaving S to fall in the window someplace.  The S mark continued at 9° BTDC until 1978 midyear production...and after Jan 1, 1978, bikes were officially 'emissions controlled' and the S mark was moved 6° BTDC, and; thereafter.  The engine camshaft (not talking about advance cam here) was changed during 1978 production too.   All these changes in the automatic advance unit, and the flywheels, is a bit confusing.   Those playing with any sort of changes to the engines, including compression ratios, camshafts, timing, gasoline octane's, and lots more, may well be trying things such as adding a bit of ignition advance beyond the F or Z marks, ETC (lots of ETC).

NOTE:  The BMW engine is very good at telling you, by noticeable pinging (pinking) of an overadvanced or poor gasoline octane condition.  Hence, it is usually acceptable to advance the timing until pinging at mid-rpm is heard, then back off a bit.   

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The important timing point for ALL single spark plug BMW's, is NOT the "S" static (idle) marking, but the MAXIMUM advance point. The maximum advance marking on the flywheel of early models is a F mark, a dot depression next to it if you have that. Later models use a LINE next to a Z marking. 

There are also markings on the flywheel for top dead center of the pistons, that is the OT marking. 

Some bikes have two lines, they are 6° separated, the limits for double images, and have other uses, not important to this article.

I am well aware that there may be conflicts here with SOME publications that talk about setting the timing at the S mark. Many years ago, the idle (or often called STATIC) timing mark (S) was used, on points machines, even the /2 magneto models, by setting the (engine off) points opening position, with an ohmmeter, or voltmeter, or test light, or even some thin paper like cigarette rolling paper. Strobes were not plentiful nor overly cheap, and the above methods sufficed.  It was always a compromise, as the range of advance and the maximum advance point are far more important. 

All BMW airheads use a very similar mechanical ignition advance assembly. The ears and timing weights hole on the timing unit tend to wear, although VERY slowly, and this tends to INcrease the amount of TOTAL timing advance available...which is usually just fine.....but may be marginal on some older BMW's, such as the R60 models, which tend to need super premium fuel, especially when carboned-up. VERY especially if one has 39° advance plate.  In fact, some of the old models are fitted with compression lowering plates, to allow use of lower octane fuels. The very mild valve timing of the R60 tends to make it more sensitive than other models.  That is because quite mild valve timing ACTS as if the cylinder pressure is higher (which it is, briefly).  The best cure for pinging, after all else has been tried, including de-coking, is conversion to dual plugging, which offers many other advantages, and FEW disadvantages...cost being just about the only one.

The following is for single plugs, NOT DUAL PLUGGED MACHINES!!:
Time the engine using a strobe light, clamp it over either plug wire, the left is more convenient.  As you increase RPM from about the advance beginning point, around 1500, below which the S mark is in the window approximately centered, the S mark begins to move upwards, and eventually you should see the Z or F mark appear at the bottom of the window, and move upwards. At some rpm it will stop rising, and THAT is the rpm of full advance. It should occur at about 3000 rpm.  If that occurs around 2000 or so, you have a /5 machine with the very early advance unit, or someone put one on your bike, or changed your springs.  The engine will probably exhibit pinging (pinking), unless you have 98 octane gasoline, give or take.  A machine that can handle the faster advance, will accelerate faster too.   Having the wider advance plate (pre -012) can help...sometimes, with power output.   Generally speaking, BMW airhead engines give plenty of warning about pinging, and in many instances a small, perhaps 3° more advance (sometimes a bit more) is advantageous...this is especially so at higher elevations.  Move the Z or F markings to about 3/4 up the window, and see.  Pinging, if it occurs, will usually show up first on poorer gasoline's, at near sea level, on a hot day, under heavy throttle, typically under 4000 rpm.

But...for STOCK setting:  If the Z LINE mark (F on earlier machines) is not centered, then make a small adjustment to the timing...by adjusting the points plate position on early models...or rotating the canister on canister models. Points MUST be in good condition and the gap set FIRST, before attempting to do anything about timing. If you have a points-in-canister model, such as a 1979-1980, be aware that the outer bearing holder MUST be in position when checking the points gap.   You should lubricate the CAM and the FELT with the proper greases, sparingly, and the inside of the automatic advance also has a grease type assigned to it.  I like a very TINY droplet of good oil on the weights pivots.   When the chain stretches, you will get double images, and performance will suffer from the engine camshaft retarding. 

With the maximum advance properly set, now check the S, idle timing. It should be approximately correct. At this point you know you have approximately the correct RANGE of advance, and if you want to, move the timing such that the Z..or F mark is a SMALL amount above the center of the little timing window, at high rpm (something above  the maximum advance rpm, so you are sure the automatic advance unit has quit advancing). Going beyond 3/4 up the window is likely to result in pinging,,,,especially with regular low octane gas and at sea level on a hot day. Those having high compression motors using premium gas should be cautious about advancing timing.   HOWEVER, the BMW airhead combustion chamber is such that it tends NOT to hide pinging from your ears.  Sometimes, depending on the motor model, year, modifications, gasoline, timing unit, ETC., one can move the mark fairly close to the very top of the window.  Be cautious.

As previous mentioned, at higher altitudes, you may well get away with a fair amount of ignition advance ... and get a bit better mileage. 

OT:  when this mark is centered, both pistons are fully out.  The typical use is for setting valves, but one must rotate the engine 360° from one cylinder ON COMPRESSION STROKE, to the other cylinder.

1981+:  LINE next to OT is TDC

S:  Static timing, lines if present are 3° from S, for maximum limits for split images

F:  Full advance, at rpm for that or above.  For 1970-1980, is a machined dot.

Z:  1981 and later, full advance, if a line is present, Z is that line.

NOTES: 
(1) The timing advance should BEGIN on the later machines at approximately 1500 rpm, and quit at about 3000.  Some books specify 1550 for the beginning of the advance.  The early /5 advance started, per SOME literature, at 1200 rpm, but some books will say advance began at 800.   Racers might be interested in that, as the advance starts right from, essentially, idle rpm.  Note that the /5 advance quits at about 2000 in some books, 2200 in others, and one factory manual even shows it quitting at 2500 rpm.    With today's poor octane gasoline, having the advance quit at the higher rpm is better, although performance suffers some.

 (2) 2 mm (.08") on the flywheel is ONE degree. The 1980's and later flywheels are called clutch carriers, and are not a continuous metal part showing in the window, but the information is same.   The R65/R45 models have a different flywheel, and the markings are deeper inside and harder to see.

(3) Later models may have two lines, one above, one below a timing character letter, these are spaced at 3 degrees from the timing mark, and are there for reference to factory spec limits. These lines are 6 mm separated (.236 inch).

(4) If your strobe light shows double timing images:   that can be due to one or a combination of the following: worn timing chain, bent cam tip on NON-canister models, worn automatic advance unit, unequal timing bumps of the two bumps on the cam of the automatic advance unit.

(5) 1979 and later models have either points (1979-1980) or a Hall Element (a type of transistor that is magneticly sensitive) in a canister, driven by a new style nose of the camshaft:  flat, with OFFSET keyway.  You can NOT put the canister back with the keyway wrongly engaged due to the offset.  The type of drive used is more stable, and cam tip irregularities are a thing of the past.  The automatic advance units in these canisters is well known to get gummy or otherwise stick in an advanced position, usually this happens after FULL engine warmup, and the engine will idle way too fast.   You may be able to remove the small oval plate on the side and spray in some oil (NEVER WD40), and fix the problem, or for awhile.  A full disassembly and cleaning is the proper answer, sometimes with some minor metal burnishing.   The effect is provable by slowing the engine using a stop like a brick wall in front of the front wheel, and easing the clutch to slow the engine to normal rpm....if the strobe shows advanced timing, you found your problem.  An article on the canister and electronics will be found here at:  Ignition.htm

(6) Ignition cutout problems after some miles down the road on 1981 and later models is quite often due to a failure to clean off, and replace, the transistor-type heat sink grease, located beneath the ignition module, which is under the fuel tank.   Every year or three is probably OK.  Allowing this cutting out from excessive heating to continue too often will result in module failure.  Radio Shack has heat sink grease.

(7) Some airheads used TWO each 6 volt coils, with a primary of about 0.7 ohm.  Those with a single dual-output-tower coil, had 1.25 ohm.   

There were TWO types of 6 volt coils, be sure to use the proper one, they are different for points versus electronic module.  The old black Bosch coils, with the lightning-bolt on the side, which are 12-13-1-244-142 (these coils are NOT marked 6 volt), are the best ones to use with the electronic module ignition.   In all cases of using two separate single tower coils, terminal 15 on one coil goes to terminal 1 on the other coil.  That leaves one terminal 15, which is for the GREEN lead; and the remaining terminal 1 lead goes to the BLACK lead.    

If you are replacing a dual output stock coil with two separate lightning-bolt coils (see above paragraph), you will have to fashion mounting...one can go where the original coil was, the other to the rear....under the relay bracketry.  Have the rear coil fire the right plug.  

Do not use the coils marked 6 volt, nor the Bosch blue coils, for the module.

Coil secondaries are about 4000 ohms for the two separate coil models, and 8000 for the twin tower single coil model.   The early GRAY bodied twin tower coil (Bosch 0.221.500.200) greatly tended to fail, by cracking, and wires would be cut by cracking, and/or moisture could enter.  Lots of ignition problems from those coils, including the acting up of the electronic tachometer.  You can use an Oilhead coil, or for ease in installation just use the updated coil for the airhead which is 0.221.500.203, and is sold by BMW under part number 12-13-1-244-426, it looks a bit different, but fits just fine.    For any coil, clean the top now and then, maintain a good rubber boot fit and condition, and inspect the metal contact at the bottom of the tower after removing the boot (inspect wire clip too)...clean off any corrosion, use a bit of silicon grease to help prevent that.

NOTE:  a common reason to install the lightning-bolt coils is that a stock grey-bodied early twin tower coil has cracked, and started to fail, usually with moisture conditions.  If you can dry out the coil, you can epoxy or otherwise seal the crack....but this is a very temporary fix....and sometimes will not work.  If the coil has OPENED its secondary winding, this still may work to get you home.

(8) Early spark plug caps were about 1000 ohms, and are fine for any POINTS ignition bike.    ELECTRONIC module/Hall element bikes MUST use 5000 ohm caps.   Appropriate NGK caps are fine.    For the 5000 ohm caps, caps that measure 4000-8000 ohms are OK, 8000-12000 are questionable, over 12000 definitely faulty.  NEVER use resistor plugs!!!! 

(9)  It is perfectly acceptable, on ANY airhead, to short-circuit a spark plug wire CAP at its inside metal fitment, to a cylinder, to ground out the ignition.  Do it securely.  On module models you must not short the wire though, only via the 5000 ohm cap.  NEVER, on ANY airhead, allow the spark plug cap to be off the spark plug or be ungrounded as described, with the ignition ON....you can ruin a coil, and the faulting may appear months or years later.

(10)  There is a detailed article on the canister electronic ignitions elsewhere's:  Ignition but here are a few hints on troubleshooting:
The Control Unit (module) under the tank, needs fresh heat sink grease, as described above, every year or three, otherwise it overheats.   Power is supplied to this module at pin 2 (ground or -, negative 12 volts) and pin 4 (+12 volts).   Note that the ON-Run switch on the bar and the key switch must be on and in RUN position.   If voltage is present, try measuring between pins 5 (+) and pin 3 (-).  This is the trigger assembly output (from the canister).  There should be at least 5 volts, if not, the fault could be EITHER ignition unit.  If you do not have that voltage:  

Disconnect the plug from under the tank, at the module where you are taking these measurements.  In order to remove the plug you MUST remove the very thin rectangular steel bale-wire first....it simply clips around the plug assembly, there IS an opening in it, it is not a complete sealed loop.  With the plug removed, withdraw pin #5 from the plug (you will need a very thin tool to press the hidden release point tab) and then reconnect the plug.  Connect the meter, as a milliameter, between the removed wire and the module pin 4.  If the reading is 3-20 milliamperes, the control unit is faulty, if more or less than that value range, the trigger (Hall) is faulty.   

If the testing is not conclusive, or you wish to do this anyway, here is another thing to do:
   Remove the battery negative wire at the battery or transmission as appropriate, then remove the front timing chest cover, then reinstall the battery wire.  Disconnect the three pin plug assembly coming from the canister (key is off).  Same sort of bale clip here.  Remove one spark plug, and with it still securely pushed into the spark plug cap, tie the spark plug metal to the cylinder head securely.    Turn on the key.  Momentarily and repeatedly short the center terminal of the 3 pin plug (not the canister side) to engine ground, with a jumper lead.  A strong spark should occur.  If it DOES, then the problem is definitely the trigger Hall device.  

(11).   To retard the spark, turn the canister clockwise; and to advance the spark, turn it CCW.

Revisions:
02-03-2003:  complete information added on the automatic advance numbers and specifications, and some revisions made to accommodate those, and other changes to match and clarifications.
04-14-2003:  add .htm title; edit for clarity extensively.
06/29/2003:  Extensive incorporation of information moved from elsewhere's on this site.  Clarify and update that information as required.
07/13/2003:  expand #7
07/23/2003:  add #11
09/07/2003:  Expand NOTES (1)
04/09/2005:  add beginning of article note
10/07/2006:  Updated
11/28/2006:  add paragraph on points amplifiers

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