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ELA BMW MAINTENANCE NOTES
from Internet References listed below
CONTENTS
Alternator GEN Lamp |
Diode Testing | Diode Heat
Fuses Blowing
Manuals | Meters
Points, Condensers & Timing
Regulator Test | References

ALTERNATOR (GEN) LAMP
If the GEN lamp fails the alternator will not usually charge. With the ignition key in the RUN position, the battery positive (+) connects to the ignition switch, from the switch to the GEN lamp, then through the voltage regulator to the Df rotor brush. The small (due to the internal resistance of the lamp) current travels through the Df rotor brush and slip ring, into the rotor, back out the D- slip ring and brush, then to ground (chassis), making a complete circuit for the small current in the alternator rotor.

When the rotor is spinning fast enough, the alternator will begin charging, but the rotor must be slightly magnetized by the above circuit, until such rpm and condition is reached that the alternator self-energizes. Do NOT depend on hearsay that at ~5000 rpm charging will begin due to residual rotor magnetism. While that might occur, one shouldn't depend on it!

The actual circuit is slightly more complex than above. One side of the GEN lamp is fed by the battery after the ignition switch, and the other side of the lamp connects to the alternator output of the positive output three SMALL diodes on the diode board. That point is also "D+" on the voltage regulator. When the alternator is not spinning, or spinning slowly (< ~1200 rpm) the alternator output is ~zero. The lamp will then be lighted, as the battery current flows through it and then through the regulator and rotor, to engine case ground (battery negative). Once the alternator stator output increases enough, the three small diodes rectify the stator output (rectify means changing AC to DC) and the voltage on BOTH sides of the lamp is now approximately the same, and the lamp has so little voltage drop across it, that it appears UNlighted. The lamp will NOT supply nearly enough current to fully energize the rotor, that is what the small diodes do, supply the several amperes needed (abbreviated explanation here).

A dim or unlit lamp at >1500 rpm usually means some connector(s) corroded, or a bad rotor or brushes. A bright lamp at riding rpm USUALLY means a shorted rotor or bad regulator, or a bad diode board, and likely there is no charging at all.

NOTE: When one or both brushes is worn enough, the snail spring that supplies pressure onto the brush may begin to contact the plastic brush holder, and reduce pressure on the brush. A brush nearing the end of life is often indicated by a GEN lamp lighting (dimly) with slight increase in brightness as rpm rises. The reason for this is the SLIGHT wobble (called runout) of the rotor...moving the brushes in and out, and the snail spring slightly bottoming. Brushes are 16.5 mm long when new, from square end to middle of concave end, and are worthless once the spring contacts the holder.

While you could do some jumper wiring or other things to get the alternator operating in the case of a burned out lamp, it is far messier than what is proposed below. Note that if you should have a wiring failure in the lamp circuit, this resistor modification might not help.

MODIFICATION: This modification allows the lamp to fail and still have the alternator charge, so that you can replace the lamp other than by the side of the road. If done incorrectly, it will reduce reliability, and you could damage the instrument 'printed' wiring connection board...or produce a potential short circuit under the gas tank, etc. GEN lamps seldom fail!

RESISTOR: The resistor should be rated at 1 watt or more to essentially last forever. However, most have used the smaller physical size of a 1/2 watt resistor without failing. If you try to use a resistor size of more than 5 watts you may have problems fitting it into your instrument area or neatly installing it under your gas tank. There is no need for such a large physical size.

Any type of resistor may be used. It can be the old-fashioned type called 'carbon composition', or any modern type of 'film' or 'deposited carbon' type....or even a 'wire wound' type. The resistor value can be 470 ohms, but some tests indicate using 330 ohms may be better. Since the resistor value is roughly a hundred times higher than the rotor resistance, most BMW alternators can use the same value resistance, even though the rotor resistances.

Resistors normally come in standard values as 270; 300; 330; 360; 390; 470. 330 may be a good compromise between charging characteristics and heat produced. Too much heat might injure the instrument pod parts (if that is where you mount it) over the long term. The resistor is only energized with significant heat production when the alternator is not spinning and the ignition is on (pre-starting) OR when the alternator is at low rpm, idle or somewhat above. Under the worst conditions a 330 ohm resistor would produce about 0.6 watt. If mounting the resistor at the printed circuit socket and to be sure of not damaging the printed material, use a 470 ohm resistor, which will produce ~0.4 watt, under the worst conditions.

The lamp has a modest low resistance, especially when cold (unlit). The modification consists of installing the resistor (to substitute for the lamp if the lamp fails) across the GEN lamp by either of the following two methods:

1) Neatly clean the area and solder the resistor across the GEN lamp socket wiring itself. The resistor should be secure from vibration by cementing it with a very tiny bit of silicone RTV or similar. Use very short lead lengths to avoid vibrating or shorting. The resistor will produce a small amount of heat during the time the bulb is normally lit, but this is seldom over a minute in duration, and in any event, the heat amount is small...especially with a 470 ohm value (the lower the resistance, the higher the heat produced). Those installing the resistor inside the instrument pod and across the printed circuit material might well use the 470 ohm value, considering the heat, but I have successfully used a lower resistance value there.

2) Install the resistor from the terminal of the ignition coil that connects to the battery circuit. This is the terminal that has the green/blue wire. There is often an unused male spade connector available there. Connect the other side of the resistor to either of the blue wires coming out of the voltage regulator plug [this is D+]. You need to do this neatly, with no chance of bare wires, nor vibration breaking them. Insulate the resistor and wiring with shrink tubing, and use proper all-plastic wire-ties, as required. This is the preferred point of attachment, to avoid damaging the flexible circuit at the lamp (if you have a later bike with the instrument pod, not a /5), especially for the lower resistance values for the last little bit of performance. But, honestly, I have never seen overheating from the use of the lower values either. There is also less chance for ham-fisted folks to damage that thin flexible printed circuit board.

DIODE TESTING

Some devices, such as DIODES, are often tested by means of an ohmmeter. An ohmmeter...or diode function test in a meter, is NOT the only common test on diodes. Common types of simple diodes must pass current in one direction, and not in the other (or, very very little). If the ohmmeter does not apply enough voltage and also current to the diode, the diode may well not 'turn on', in the so-called 'forward direction'. This DOES happen on some [usually expensive] digital meters that intentionally use very low currents to avoid damaging sensitive devices.

The APPLIED VOLTAGE to the diode must be at least 0.5 VOLT for most common diodes to 'turn on' in one direction. Diodes, in the forward, turned-on direction, can be thought of as having an inherent internal resistance. Hence, they can, with enough current flowing, develop a lot of heat. Since the forward drop of a diode is fixed by atomic properties at roughly 0.5 to 0.6 volt; at 10 amperes that is 5 or 6 watts of heat to somehow be gotten rid for each of the 6 large power diodes in your diode board!

This heat must be cast off, which is done by the L metal ends of the diode board, into which the power diodes are pressed. The RUBBER mounted diode boards cannot transfer this heat nearly as well to the timing chest metal, itself already hot from the engine being run, which is why it is often recommended that the rubber mounts be replaced with AFTER MARKET METAL MOUNTS from..

Motorrad Elektrik or
Thunderchild

DIODES & HEAT
Semiconductor 'things' like diodes and transistors, do NOT like heat. They do not like excessive heat, and also do not like to be cycled, cold/hot/cold....This cycling tends to bring about failures in many types of electronics equipment, sometimes in intermittent ways. Constant heating and cooling may be responsible for the diode board diodes to fail.

If the the ignition module overheats due to lack of regular replacing of the heat conducting paste, usually fresh paste fixes things ..without replacing the module, but letting it overheat a large number of times can cause permanent failure. That heating is caused by the engine heat itself, as well as the current flow through the diodes.

FUSES BLOWING
including.. Using an Ohm Meter

WARNING: It is EXTREMELY dangerous to substitute fuses whose amperage is above the value specified for the circuit. Only use the value of fuse that the motorcycle manufacturer has specified for that fuse location. Electrical fires can ruin your bike. Electrical fires near gasoline tanks can kill or maime.

Since you know which electrical loads go dead when the fuse blows, disconnect the loads one at a time to see if your fuse blowing problem disappears. If a device blows the fuse when it's connected, you've found a problem. Swap in a good replacement device and retest. If the problem persists, keep looking by disconnecting other loads on the fuse.

If fuses are blowing after you've disconnected all known loads, there may be a load you're unaware of. Read the manufacturer's wiring (schematic) diagram to be sure that you've disconnected every load from the fuse.

Try disconnecting any aftermarket devices, especially if you're unsure of where they are powered from. There's a chance the device is a load for the problem fuse circuit. Most aftermarket devices have their own fuses, but that doesn't mean that they not wired onto a fused circuit.

At this point, you might not have a wiring diagram or the problem may be a bare wire that's touching something metal. You need to find and follow the wire to the fuse blowing device

Remove the fuse from the fuse holder. Turn the bike ignition on. With the black wire of your DC DC voltmeter or test lamp connected to the motorcycle's frame (electrically the same as the battery's negative terminal) you'll see 12 volts (test lamp lit) on the (un-fused hot) side of the fuse holder, and 0 volts (test lamp off) on the (fused or protected) side.

WARNING: Turn the bike's electrical system off as you disconnect and reconnect wires and making repairs. Be careful not to create some new and possibly worse problem while diagnosing. Follow good electrical practice when reconnecting wires and don't leave bare wires exposed after reconnecting them.

If you come to a splice or a terminal block that serves to split the wire into two or more wires going to different electrical components, the circuit is effectively being branched into multiple circuits, all protected by that same fuse. The fuse-blowing fault could be down any one of the circuit branches, so disconnect each branch one-at-a-time to determine which has the fault. After disconnecting a wire, put in a good fuse and see if it blows. When a good fuse doesn't blow, you've identified the disconnected wire as the circuit branch with the fault. If the new fuse blows, reconnect that wire and disconnect the next wire (circuit branch).

Re-connect the wire with the circuit fault and follow it until it either branches or it arrives at it's electrical load. If the wire branches again, you'll have to disconnect each one of the branches and re-test..

When you finally get to the electrical load at the end of the wire, disconnect it and the fuse should no longer blow. Try replacing the load device to solve your fuse problem.

Safer Method, Using an Ohm Meter for Diagnosing Blown Fuses:

This is done in much the same way as previously outlined, but with the motorcycle ELECTRICAL SYSTEM OFF. Ohmmeters don't like to see voltage on the same wires as themselves. We will follow the fault by the "ohmic" value at the wire of the faulty circuit. This method is difficult because you have to interpret if a low ohmic value you see on your meter is from the fault or just the correct value of a light bulb orother low-resistance load.

No electrical resistance (zero ohms) is what is commonly referred to as a "dead short" or "short circuit."

Just like the first method, you will follow the "fused circuit" away from the fuse holder. When you get to a terminal block or splice, you'll disconnect each wire (circuit) one-at-a-time again. But instead of powering up the bike and blowing fuses, use a low ohms range of your multimeter to measure the ohms (resistance) of each circuit. You should always see some resistance, although it may be small.

The BLACK WIRE of your multimeter should be connected to the motorcycle's frame (which is electrically the same as the battery's negative terminal).

There are no hard and fast values to look for when chasing a fault. Zero ohms (absolutely no resistance) on a circuit branch is bad and would be the most likely suspect. If none of the circuits reads zero, hopefully one will be significantly lower and close to zero. The majority of the current (probably blowing the fuse) flowing through the fuse is going through the wire with the least resistance in ohms.

Just be sure that your meter is set to read a very low amount of ohms. On a high resistance range, say one that reads up to 10,000 ohms, a few ohms might look like zero, and you could follow the wrong wire. Auto-range meters won't have this problem.

When you've found a wire (circuit) with a very low or zero resistance, disconnect the load. Put in a good fuse and power up the bike to check if you've found the problem. In the event the fuse still blows, you've either somehow gotten off track or the problem is a short ie, pinched wire (insulation has been compromised and wire is touching metal) leading to that electrical load. A pinched wire will have a reading of zero or negligible resistance. The wire itself may have some negligible resistance, maybe one tenth of one ohm.

To check for a short, turn the power off to the bike. You've already removed the electrical load at the end of the wire, so go back one step and disconnect the wire at the previous splice or terminal block. Measure the resistance of the wire. It should be infinitely high because there is no load at the end of it. If it reads zero ohms, you've found the wire that's pinched. If the wire checks out OK, but you're sure that the fault is along the wire you're chasing, you'll need to go back and check each branch of the wire back to the fuse in the same way.

One of things that makes this method so difficult is the nature of the electrical loads you're going to encounter. You should know that light bulbs contain wires called filaments that connect the wire (circuit) from the fuse to the motorcycle frame (electrical ground) in such a way that the filaments glow from the current (amps) flowing through them. When you are measuring the ohms of a wire leading to a light bulb, it may measure just an ohm or two. That's because the ohmic value of the filament wire inside the light bulb is very small.

Heated grips use conductive material that may also present a low ohmic value. A relay's main component is a coil of wire that may not have a lot of resistance.

To make things a little more difficult, when there are two or more light bulbs on the same wire (like parking lights or instrument cluster lights) they work against you because they combine together to make the measured amount of ohms on the wire look even smaller (closer to zero ohms) than that of a single bulb by itself.

Now you're aware that many different electrical loads will make the wire look almost like a pinched wire to the ohmmeter.

In the case of a single light bulb at the end of a wire you can pull the light bulb out of it's socket and measure how many ohms it has to know how many ohms you should see on the far end of the wire going to it.

MANUALS
The Chitech electrics manual and the owners book or factory schematic, are THE two BEST sources. The Chitech (from Chicago Region BMW Owners Assoc.) Manual (BMW Electric School Manual) is THE best manual for BMW electrical:

crbmw.org: ChiTech

In our BMW bikes, the resistance of the GEN lamp has an additional, not usually mentioned purpose, that of restricting the maximum possible current flow.

METER MEASUREMENTS

VOLTAGE does not require disconnecting wire between meaurement points and is typically measured by allowing a small amount of the current to be diverted from a circuit under test, and applying that diversion to some sort of meter, in such a way as to have a calibrated reading. SOME meters divert so little current that the voltage is not changed by attaching the meter (where the source being measured is of low internal resistance, such as almost every area of a vehicle, NOT true of the electronic ignition, which has areas you should not try to measure). Analog meters with meter movements usually drawmore current, is still NOT a problem with MOST areas of vehicles.

Do not purchase a meter unless it tests DIODES adequately. The readings on a meter that do NOT turn on diodes properly might be so weird as to be unusable.

INSTALLATION OF POINTS, CONDENSERS, AND TIMING (1970 - 1980)
March 16, 2000

Notes from ( EurotechMotorSports.com) an article by..

Bob Clement
Bob's Motorwerks
HC48 Box1083
91Blanchard Butte Rd.
Roberts, Montana 59070
406-445-2044
Email: bmwmontana@aol.com

INTRODUCTION:

The author disclaims any responsibility for accident or injury resulting from using this article and working on your own bike.

This article was written on the most basic level.

If you are only resetting your points and timing and not installing new points extract the relevant information.

Part I is for 1970 thru 1978 models and Part II is for 1979 and 1980 models. Details related to spark advance mechanisms and other material relevant to points installation and timing are included. Read through the article to obtain tools and materials needed before you start. The necessary tools are in the original ol kit from your bike. There are a couple which your kit may not have:

Feeler Gauge for setting point gap. Use the 0.40 blade, otherwise obtain a set of feeler gauges from an auto parts store. Uuse the blade marked .016" or .40mm. For 1970 - 1978 Beemers, it will be useful to bend the tip of the blade about 20 degrees or so. With 1979 - 1980 model do not bend the blade.

Points Cam Lubricant: needed if not with the new points set

Timing Light with an independen power source for stting the timing

PART I
1970 - 1978 models

STEP I: Initial preparation

On all models, first disconnect the negative battery wire to eliminate shorting out and destroying the diode board under the engine's front cover

Remove the 10mm headed bolt which holds the negative battery cable to the transmission. This bolt also holds the speedometer cable in place and is located on the right side of the motorcycle at the back of the transmission, just forward of the rubber bellows which encloses the universal joint. The bolt has a hole in it because this bolt is also a transmission breather. Blow thru the bolt to ensure that it is open. This hole is also a place where water can enter the transmission (especially when using a high pressure car wash). Never use a high pressure washer to clean a BMW. After removing the bolt and freeing the negative cable put the bolt back in most of the way with your fingers.

With a pair of side cutters, nip a piece out of the metal loop at the end of the ground strap to create an upside down U. This will allow you to simply loosen the breather bolt a turn or two and lift the ground strap off the bolt instead of always having to take the bolt clear out, thus helping to prevent accidental crossthreading of the bolt or stripping of the threads in the transmission.

Take a look at the little bell shaped rubber boot which the speedometer cable passes through where it enters the transmission. Is it cracked? Does it fit tight around the cable. This is the other main place which water enters the transmission. The boot is available thru Eurotech and is very inexpensive, much cheaper than a transmission overhaul. If you can't replace it at this time lift it up and pack some grease into it.

At the front of the engine and remove the Allen head bolts that hold the front cover on. Remove the front cover.

STEP II: Removal of Spark advance, points, and condenser

Under the removed coveris the diode board at the top of the engine, the alternator in the center, and the spark advance mechanism with points sitting behind it at the bottom

Remove the nut and wavy washer from the spark advance mechanism with a 10 mm wrench. Remove the points by removing the straight slot single screw which secures them to the points plate. Now remove the slotted screw at the 6 o'clock position at the bottom of the points plate. This screw should be holding a small metal strap under which passes the points wire. The wire enters a rubber tube at about the 10 o'clock position of what we shall hereafter refer to as the points chamber. There is a square section rubber strap which fits into a groove going around the points chamber. The rubber tube (AKA the elephant trunk) and the rubber strap around the point chamber are both very important for keeping the points chamber free of water. Inspect them both. If the large end of the elephant trunk is damaged and doesn't fit in its recess in the points chamber or in its corresponding recess in the front cover of the engine, replace it. It helps on reassembly to glue the elephant trunk into its recess in the points chamber using 3M weather strip adhesive. Clean the square section of the rubber "trunk" with a paper towel and some rubbing alcohol before gluing it in place so the adhesive will stick better. Follow the instructions on the tube of adhesive. Also inspect the rubber strap that encircles the points chamber. If it looks like it won't seal well against the front case and keep water out, order one and change it. If the "trunk" is held in place well when you go to take the points wire out leave it there and unplug the wire from the condenser and snake it down out of the "trunk," remove the points. There should be a metal strap holding the "trunk" at the top. The screw that holds the metal strap in place also holds the condenser in place. Remove that screw at this time. After removing the second wire from the condenser, you can remove the condenser. Inspect the spark advance mechanism. Look for signs of rust pitting on the cam lobe surfaces of the mechanism. If it is pitted it should be replaced as the pitting will quickly wear the rubbing block of the points and cause the points to close up and retard the timing. If the cam isn't too badly pitted it can be well lubricated with points cam grease and tried. You will just have to monitor the timing for changes for a while to determine if the pitting is going to be a problem. Replace the spark advance springs with BMW heavy duty ones. BMW part number 12 11 1 356 546 ($5) STEP III: Installation of new points and condenser & setting the points gap.

Take the new points and feed the wire up thru the "trunk" (rubber tube) and attach the wire to one of the tabs on the condenser. Mount the new condenser and the metal strap that holds the "trunk" with the screw you removed from there. Attach the other wire to the condenser. You will note that the points wire has a sheath around it which can be moved up and down the wire. Move the sheath down the points wire until it bottoms out against the points. The points have a round pivot sticking out the back about a 16th inch. Be sure the pivot sits in its hole in the points plate when you mount the points to the plate. Secure the points to the points plate with the short screw you took out earlier. Just snug the screw down a bit, not too tight because you'll be adjusting the points shortly. Install the screw you took out of the plate at the 6 o'clock position complete with the metal strap that holds the points wire. Apply a small amount of points cam grease to the two lobes of the points cam and on the rubbing block of the points.

Install the spark advance mechanism on the threaded nose of the camshaft. The hole in the advance mechanism is not totally round, it has a flat side. The end of the engines camshaft where you will be mounting it has a corresponding flat side. Line the advance mechanism up accordingly and slip it on end of the camshaft. Put the wavy washer on and then the 10 mm headed nut. Tighten the nut.

WARNING: DO NOT OVERTIGHTEN THE NUT. It is possible to break the end off of the cam. Just snug it up and be careful.

To set the point gap, put your 6 mm Allen wrench in the hole in the nose of the alternator to turn the engine with. Also remove the spark plugs at this time to make it easier to turn the engine with the Allen wrench. Facing the front of the engine, use the Allen wrench in the alternator bolt and turn the engine clockwise. When the face of the spark advance mechanism is sitting at a slant pointing at the 11 o'clock and 5 o'clock position you should be able to set the points. This positioning of the spark advance mechanism should give you fully open points as well as access to the points around the right side of the advance unit. A small notch is built into the points assembly at the top and just above the notch there are two small nubs sticking out from the plate that the points assembly is mounted to. Take a flat blade screwdriver and put it in the notch in such a way as to be able to pry gently back and forth against the nubs and cause the points to open and close. Open the points a little and slide the feeler gauge between them (.016" or .40mm).

Adjust the gap until the points just drag on the feeler enough to be detected, then tighten the screw which holds the points in place. After tightening the points check the gap again, sometimes it changes when you tighten the screw. A good technique to use, once the feeler is held by the points, is to release the feeler and then grasp it again and feel for a small amount of drag. The reason for doing this is to be sure you have the feeler in straight and not cocked to one side which will give you a false feel of the drag on the feeler gauge.

Once you have the setting, turn the Allen wrench in the alternator clockwise again until the spark advance has gone one half turn around and the other lobe of the advance cam (there are two) opens the points fully. Check the points gap on this side of the advance cam. It should be pretty close to the same as the first setting which you did on the other lobe of the advance cam. Possibly no matter how many times you check the point gaps, they will be VERY different on each side. One side of the cam might open to .016" and the other side to only .010" or maybe to .020". Set the side that opens the widest to the correct setting of .016" (.40mm) and proceed, even if the other side of the points cam only opens to .012" or some other gap of less than .016". These symptoms mean that the end of the engine cam on which the points cam is mounted is not traveling true. In other words it wobbles a bit. Chances are that even with this variance, the bike will run very well. With this wobble present you will see a widely spaced double image of the timing mark when we get to that step.

It is possible for an EXPERIENCED mechanic to at least partially if not totally eliminate this wobble. That procedure will not be discussed because it can result in the accidental breaking off of the nose of the engine camshaft. This wobble is a VERY COMMON in 1970 - 1980 boxers and is of little concern. If you must, take it to a trusted BMW mechanic.

Once the point gap is set it's time to set the timing. Reinstall the spark plugs.

STEP IV: Setting the timing.

Connect the timing light following the manufacturer's instructions.

WARNING: USE A SEPARATE BATTERY TO POWER THE TIMING LIGHT. AN ACCIDENTAL SPARK WHILE CONNECTING THE TIMING LIGHT TO THE BIKE BATTERY CAN CAUSE AN EXPLOSION. BATTERIES CONTAIN ACID AND PRODUCE EXPLOSIVE GASSES. THERE IS A RISK OF SEVERE INJURY OR WORSE.

Reconnect the negative wire from the battery to the bolt at the right side of the transmission where you removed it. Remove the black rubber plug from the left side of the engine near the left carburetor so that you can view the flywheel. Note that there is a line etched into the left side of the hole. That's the line we will be lining the timing marks of the flywheel up with. Make sure you have removed the Allen wrench from the alternator. Reinstall the spark plugs. Tighten all of the screws that hold the points plate and the points.

Put a fan in front of the bike to help keep things cool. Start the bike. Run the bike as little as possible during the following procedure to keep from overheating. Hold the throttle open a little bit to keep from stalling the engine.

Aim the timing light at the timing plug hole in the left side of the engine and rev the engine slowly up to 3500 rpm or so. You should be able to see the F timing mark in the hole. The F mark will have a dimple in the flywheel right above it. That is the mark we will be lining up with the mark at the left side of the timing plug hole. If the F mark is above the hole you will need to retard the ignition a bit. If you see the F mark dimple in the bottom of the hole the timing needs to be advanced. If you see 2 F marks that's OK. We will try to "split the difference" and center the space between them on the little line which is visible on the surface of the left side of the hole. When you idle the engine down to 1000 RPM or below you should see an S mark.

If you see OT, that is the top dead center mark and the timing is probably too retarded. We are not as concerned about making the idle timing mark line up exactly with the line on the edge of the hole as we are about getting the F mark on the money. To change the timing, that is, to retard or advance the timing we are going to move the plate that the points are mounted to. We will move the plate clockwise (as seen from in front) to retard the timing and counterclockwise to advance the timing. If you don't see any marks in the hole you will just have to move the timing around until you see the marks and can do a final adjustment.

TURN THE ENGINE OFF and go to the front of the engine.

WARNING: BE VERY CAREFUL WHEN MESSING WITH THE TIMING WHEN THE ENGINE IS HOT....THE EXHAUST PIPES WILL BURN YOU BEFORE YOU EVEN FEEL IT...YOU'LL HEAR IT FIRST!!!! LIKE PUTTING SPIT ON A HOT IRON!!!!

Insert the Allen wrench in the alternator again and turn the engine clockwise until you can get at the screws which hold the points plate. They are at the 12 o'clock and 6 o'clock positions and are set into holes which are elongated to allow movement of the points mounting plate. Loosen them a turn or so. Now, look at those two little nubs you used to adjust the points gap with. Move the plate a little whichever way you need to. Take a smallish screwdriver and a small hammer and place the tip of the screwdriver against one of the nubs and GENTLY tap the plate in the desired direction. GENTLY IS THE WORD since it is possible to break the nub off. Also be careful to not put the tip of the screwdriver on the points assembly, only on the little nub, because tapping on the points assembly might move the points a little and change the gap you set. Retighten the two screws and go back to the timing hole. Start the engine and check the timing.

Continue this procedure until you successfully get the F mark indicator to line up with the scribed mark in the timing hole at 3500 RPM or so. If you have a "double image" of the F mark just set the timing so that you split the distance from one F mark to the other. Further reving should not move the mark much although it may move up in the hole just a little at higher revs.

When you are satisfied and have tightened all screws without any change in the timing, shut the engine off and disconnect the timing light. Put the timing hole plug back in place and disconnect the ground wire at the transmission end again. Let the engine cool a bit before installing the front cover due to HIGH RISK OF EXHAUST PIPE BURNS.

Reinstalling the front cover: If you have a pre 1978 bike with a mechanical tachometer there is hole in the top of the front cover which goes over a pin protruding from the engine. There is a rubber grommet around the tach cable which is slotted and fits into the engine case and also onto the front cover... and the black hose (remember the elephants trunk?) which the points wire passes through which all have to be dealt with while installing the cover. It is important that the square section of the "elephants trunk" be fitted properly into both the engine casting and the front cover. Just take your time......humans CAN accomplish this. Once the cover is in place put the Allen screws in place which secure it and snug them up. Now reconnect the negative battery cable, put the spark plugs back in and go for a ride!!!!!!!!!

If you have a post 1978 bike you only need to deal with the cover locating pin and the "elephants trunk." Secure the cover, reconnect the battery negative wire and go for a ride!!!!!

PART II

1979 and 1980 Models

STEP I: Initial preparation.

Go to PART I and complete STEP I.

oints and condenser.

After removing the front cover, you will see the diode board at the top of the chamber, the alternator in the center, and the canister containing the points at the bottom. You will notice that the condenser is mounted on the outside of the canister. It is the cylindrical can with a wire going to it. Pull the wire off the tab it is attached to. Remove both spark plugs. Take a 6MM Allen wrench and put it in the Allen bolt in the nose of the alternator. Go to the left side of the motorcycle and remove the black rubber plug (timing hole plug) from the side of the engine. It is located near the left carburetor. Through this hole you will be able to observe the flywheel. The engine timing marks are on the flywheel, although you may not yet be able to see them. Squat or sit down facing the left side of the bike (left side as you sit on the bike) and with your left hand turn the engine with the Allen wrench. Turn it in a clockwise direction (clockwise as though seen from in front of the engine) and watch for marks on the flywheel. You may need to use a flashlight for ease of viewing. Turn until you see the S on the flywheel. There are 3 lettered marks on the flywheel and some little lines or dots near them. The 3 are: an F mark with a dimple above it, an S mark with some lines and just beyond the S mark the letters OT. For now just find the S mark and line it up with the line you will see inscribed into the left side of the timing hole (at the left center of the hole). After the S mark is located and lined up with the timing hole mark go back to the front of the engine. The easiest way to install the new points is to remove the canister from the engine. Take a 4MM Allen wrench and remove the two Allen screws which hold the canister in the engine and put them aside. Since you previously removed the wire from the condenser you will now be able to grasp the canister and pull it out of the engine. Take the canister to your work area and place it on a clean surface. It's not a bad idea to put a rag or towel down to put the canister on so removed parts will not have a tendency to roll away. Take a Phillips screwdriver and remove the two screws which hold the cover on the canister. Remove the cover. Right under the cover is another plate which the cover screws screwed into, and it is held in place with two standard screws. Notice that there is a slot in the plate with a locator pin sticking up into it. Just note to yourself how the plate is located on the canister before you remove it to make things simpler on reassembly. Go ahead and loosen the two slot headed screws and work the plate up and off the shaft which sits in the center of it. You will now see the points down in the bottom of the canister. Remove the wire which goes from the points to the tab on the side of the canister and take note of which way the tab faces. Remove the screw which holds the condenser to the outside of the canister and remove the condenser complete with the plastic block that has the two metal tabs that the two wires went to. Now remove the slotted screw that holds the points into the canister and lift the points out. STEP III: Installing the Points, Condenser, and reinstalling the canister.

If there is any sand or other unwanted material in the canister clean it out at this time. Put a small amount of points cam grease on the rubbing block of the points (that's the little dark brown or black foot' that sticks down from the moveable point. You will notice that one of the points is fixed to the mounting plate of the point set and the other point is mounted on a springy arm and the arm can be moved.) Also put some of the grease on the two lobes of the point cam which is on the center shaft of the canister. As the shaft turns the lobes push on the rubbing block of the points and cause the points to open. OK. Now install the new points in the canister with the slotted screw you removed from there. Lightly tighten the screw. We'll make it tight later. Your new condenser probably won't have the block (with the two tabs) mounted into the U shaped holder on the side of the condenser, so do that now. Mount the new condenser to the outside of the canister with one tab of the block sticking into the canister. Tighten the securing screw. Reach down into the canister and push the points wire onto the tab on the condenser block. Now put a thin film of light grease in the bushing in the center of the plate you removed from the open end of the canister and put the plate in place and tighten the two slotted screws which hold it. Remember to mount the plate properly with the metal tab from the canister sticking up into the slot in the plate.

The next step is to set the points. Use a points type feeler gauge as described in the introduction to this article. Take hold of the fixture which sticks out of the bottom of the canister and turn the shaft until the points cam lobe pushes on the rubbing block of the points and opens the points. Now look closely at the points assembly. At the end where the points themselves are there is a small notch. If you insert the tip of a small screwdriver into the notch you will be able to easily pry back and forth and make the points gap open and close (if the screw which holds the points in place is left just a little loose). Open the point gap a little bit and insert the feeler blade between the points. Adjust the gap to .016" (.40mm) until the points just lightly hold drag on the feeler blade as it is removed. Tighten the screw which holds the points in place. Turn the shaft around again so the other points cam lobe reopens the points as far as they will go. Check the gap again. When you are satisfied that the gap is .016" ( .40mm), it is time to reinstall the canister in the engine.

Is the S mark still visible in the timing plug hole in the left side of the engine? If not, put it there. Now put a little oil or grease on the black O ring at the bottom of the points canister. Now look at the thing which sticks out of the bottom of the canister. Notice that it has two little metal feet which will go into a slot inside the hole in the engine. Notice that they are offset a little, they're not in the middle of the round plate you're looking at. Now look at the slotted piece in the engine you're going to insert the feet into. The slot isn't in the center of the round plate. Line up the feet and the slot in the plate appropriately and slide the canister into the engine, it should push clear in until the base plate of the canister is flush with the engine case. Take the two 4mm Allen headed bolts and their washers which you set aside earlier and put them into the slotted holes at the base of the canister. Lightly tighten them, but leave them loose enough that you can turn the canister back and forth in the engine. Hook up the wire from the engine to the tab on the condenser. Turn the canister all the way to the right (clockwise) in its slotted holes. Now using a flashlight if you have to, look into the canister and turn it slowly counterclockwise until you see the points just begin to open. At this point tighten the 4 mm Allen screws which hold the canister in place. Install the canister cover. The screw holes in the cover will line up in only one spot. You are now ready for the final timing of the engine.

STEP IV: Setting the timing.

Hook up the timing light following manufacturers instructions. It is advisable to use a battery other than the battery in the motorcycle for the timing light due to the RISK OF EXPLOSION OF THE BATTERY IF YOU SHORT THE LEADS OF THE TIMING LIGHT TO EACH OTHER OR TO THE MOTORCYCLE. BATTERIES CONTAIN ACID AND EXPLOSIVE GASSES WHICH CAN EXPLODE CAUSING SEVERE INJURY OR DEATH. FOLLOW MANUFACTURERS INSTRUCTIONS WHEN USING A TIMING LIGHT. Once the timing light is hooked up, reinstall the negative battery cable to the bolt where you previously removed it. Put the spark plugs back in. Did you remove the Allen wrench from the nose of the alternator? If not, do it now. It is advisable to place a fan in front of the motorcycle to help with cooling. Run the engine as little as possible when doing the timing to avoid overheating. Now you may start the motorcycle. Shine the timing light beam into the timing hole on the left side of the motorcycle. When you rev the engine to 3500 rpm or so the F mark should appear in the hole. Again, there is a small dimple just above the F mark on the flywheel. The goal is to get the dimple to align with the mark on the left side of the timing hole when the engine is at 3500 rpm or a bit higher. If the F mark appears above the hole, you will need to move the canister clockwise (viewed from in front), if the F mark appears at the bottom of the hole you will need to move the canister in a counterclockwise direction. BE EXTREMELY CAREFUL WHEN MOVING THE CANISTER WITH THE ENGINE RUNNING. THERE IS A SIGNIFICANT RISK OF SEVERE BURNS IF YOU TOUCH THE EXHAUST PIPES!!! Once the timing is correct, shut the engine off and tighten the 4mm Allen bolts which secure the canister. Start the engine once again and recheck the timing. Now shut the engine off and once again disconnect the negative wire from the transmission. Now you may reinstall the front engine cover. When that is completed reattach the ground wire and go for a ride!!!

TESTING VOLTAGE REGULATORS
Notes from SnowBum or AirHeads.org: Technical tips

Almost any voltage regulator found in a junkyard car that your plug fits into, will work. There are sources for adjustable and non-adjustable ones. Just one of these is the Borg-Warner (Pep Boys, etc.) R588.
The less expensive and adjustable Transpo IB301A can be found at:
Transpo-USA:   IB301A REG BO 12V replacing OE BOSCH

TESTING:

Method 1)
Make a jumper wire to keep riding tool kit using 2 standard male spades and a ~4 in. piece of wire. If the regulator fails on the road, you can temporarily ride at low rpm, with the regulator jumpered as decribed below, if the battery does not overheat.

Start the engine and check the voltage across the battery terminals with your voltmeter or bike's voltmeter (the fairing voltmeter may read ~0.3 volt lower) at sufficient (greater than 1500) RPM. If the alternator and does NOT produce at least 13.6 Volts or so, the alternator, regulator or diode board could be at fault.

Unplug the voltage regulator. In the socket (not the regulator) jumper the opposing two female's, they are likely blue and blue with black stripe.

With the socket jumpered, start the engine and slowly raise the RPM while monitoring the battery voltage. The GEN lamp should go out, and voltage rise very fast, especially if the battery is near fully charged. Don't leave the engine at high rpm long, as 15 volts will overheat the battery. This test bypasses the regulator so the alternator will put out its maximum. If the alternator produces plenty of voltage compared to the unjumpered measurement, the regulator is faulty.

Method 2)
The following generic method requires an an variable (adjustable) DC power supply. The power source must supply enough current to operate the lamp load (see below). Obtain any of the voltage regulators on the airheads, Bosch mechanical, electronic, or Wherle electronic, or any aftermarket regulator out of a car, etc. You do not need a high stability regulated power source, but the voltage should be a 'clean' DC (not too much A.C. noise). Most 'bench' power sources with any sort of built-in (or manually adde) capacitor filter will do.

NOTE: Electronic regulators can be used on all years of /5/6/7 and later airheads. Electronic regulators are capable of passing the increased current demand of later low resistance rotors, and will have no problem with the earlier /5 and /6 type higher resistance rotors. Mechanical regulators (emergency measure only, since vibrating/arcing contacts could possibly disturb the electronic ignition) used with a 1981 or later rotor possibly won't last.

The regulators all have 3 male spade connections. One is marked D+, one is marked Df, and one is marked D-. Connect the variable DC power supply positive (+) output to D+; and the negative (-) output to D-. Connect an accurate digital voltmeter to the same terminals. It is best to connect that voltmeter at the regulator terminals, not at the power source terminals.

Connect a load, 70 watt (5 amps at 14 volt) or less, between Df and D-. I recommend a (nominal) 12 volt lamp...such as an old car headlight, or a taillight bulb in a convenient socket, etc. You will be 'looking' for a triggering point, and test circuit readings will likely change at that triggering point. DO NOT use a resistor and another voltmeter, etc. as the load.

Turn on the power source, and slowly increase the voltage, noting that the lamp will begin to glow, getting brighter. When the voltage reaches the 'regulating' set level, the lamp will turn off. Note the voltage just before the light extinguishes. Check several times. The power supply MIGHT JUMP UPWARDS when the lamp turns off, requiring as estimate. You should be able to get within 0.2 volts of correct value.

REFERENCES:

AirHeads.org, Technical Tips

The basics of BMW Motorcycle electrical trouble shooting By Jim Franzen

EurotechMotorSports.com, Tech Corner
• installation of points, condensers, and timing of 1970 thru 1980 BMW SnowBum, Index of Technical Articles