I am updating the engine electrical components: diode board, alternator stator, alternator rotor, alternator brushes and all the associated wiring which is available as a kit from Euro Motoelectrics. There are higher wattage alternator kits available but I chose to stick with the stock output 240 watt, 17 amp kit.

I show removing the existing Dyna III electronic ignition, but this write-up does not cover the installation of a new Dyna III electronic ignition and the refurbishment of the timing advance unit, otherwise known as the automatic timing unit, ATU. Due to the conditions I found inside the points housing and the existing Dyan III ignition, I chose to replace it with a Dyan III electronic ignition kit available from Euro Motoelectrics.That work is documented here:

• 12 BMW 1977 R100RS Install Dyna III Electronic Ignition-Refurbish Automatic Timing Unit (ATU)

I rebuilt the starter motor; replaced the brushes, armature bushings and repainted it. You can read about that work here:

• 12 BMW R100RS Refurbish Starter Motor

The work in this write-up was done at the same time I replaced the timing chain, crankshaft sprocket, nose bearing and the front crankshaft, camshaft and tachometer drive seals in the the timing chest cover. You can read about that work in this write-up.

• 11 BMW 1977 R100RS Replace Timing Chain, Crankshaft Timing Gear & Nose Bearing

All the work in this write-up can be performed without removing the timing chest cover.

Problems Identified During Disassembly

The points housing was full of corrosion and there was corrosion in other areas of the timing chest as well so I suspect water got inside and sat for awhile.

There is a lot of oil on the timing chest cover near the tachometer drive housing so I will replace the tachometer drive oil seal when I remove the timing chest cover to replace the timing chain.

The Dyna III points use a rotating magnet attached to the automatic timing unit (ATU). This one showed signs of rubbing against the left stationary pickup on the Dyna points plate.

And the ATU shows corrosion and rust, so water was inside the points housing for some time.

I am concerned the reason for the abrasion on the Dyna III magnet sleeve that mounts on the ATU cam is because the camshaft nose is bent. I check the cam shaft nose run out after I remove the timing chain to see if the shaft is bent, and it isn’t so the wear on the Dyna III ATU magnet sleeve is not caused by a bent camshaft nose. 🙂

[VIDEO: CLICK TO PLAY]

For reliability, I replace the Dyna III electron ignition with a new unit from Euro Motoelectrics as the pickup and rotating magnet may have been damaged by water and misalignment. Dyna specifically warns that water can corrode the printed circuit on the pickup unit that mounts inside the points housing causing ignition failure. The link above shows how I refurbish the ATU and install the Dyna III electronic ignition.

This bike has the notorious rubber diode board mounts that are broken. I replace them with solid metal mounts available from Euro Motoelectrics. A previous owner used zip ties to secure it and avoid replacing these mounts which is rather difficult to do unless the timing chest cover is removed as I found out when I replaced them on the 1983 R100RS.

I’m removing the timing chest cover so I can replace the timing chain, the crankshaft nose bearing and the crankshaft sprocket, and the crankshaft, camshaft and tachometer drive oil seals. That work is documented separately.

Parts List

The following are the parts I installed.  I got the electrical parts from Euro Motoelectrics, a local company with an ever growing stock of BMW parts for airheads and newer models.

Part #	Description	Qty
EDL1-ALTKIT107	EnDuraLast I Alternator Kit 107mm, 1977-1995; 240 watt, 17 amp   Euro Motoelectrics – BMW Rotor: 12 31 1 244 642 – BMW Stator: 12 31 1 244 641 – BMW Diode Board: 12 31 1 244 062, 063 – BMW Voltage Regulator: 12 32 1 244 409 – Associated Wiring	1
BOALT-Mount131	Solid Mounting Studs x 4 (12 31 1 358 131)  Euro Motoelectrics	1
61 11 1 243 195	ENGINE WIRING HARNESS (to 09/78)	1
61 13 1 352 095	RUBBER GROMMET (to 09/78)	1
11 14 1 262 644	SEAL STRIP 1976-1978 MODELS	1

Special Tools

The diode board mounts can be replaced without removing the timing chest cover as I show here when I replaced them on my 1983 R100RS. It’s a frustrating procedure that requires patience.

• 12 BMW R100RS Check Diode Board, Replace Rubber Mounts

Since I am replacing the timing chain, I removed the timing chest cover with Cycle Works tools for removing the cover and crankshaft nose bearing and timing gear, so it was very easy to replace the mounts with metal ones.

• Cycle Works Airhead Engine Front End Tool
• A dial indicator with clamp (Harbor Freight)

Removing Engine Electrical Components

My engine is removed from the frame, but this work can be done with the engine in the frame.

WARNING:
Always remove the battery ground wire BEFORE removing the front engine cover. If the cover contacts the diode board it will ruin it.

The picture below is from my 1976 R75/6 and the components are the same as those used in the 1977 R100RS. From bottom to top is the DYNA III electronic points with the stock automatic timing unit. Above that is the alternator assembly consisting of the stator housing, stator, rotor and brushes. At the top is the diode board.

The condenser is mounted between the alternator and the diode board.

And, this is how the diode board in the R100RS was attached after the rubber mounts sheared.

Remove the DYNA III Electronic Points Assembly

The DYNA III points assembly attaches exactly the same as the stock points plate and automatic timing unit (ATU) do. The points are a bit corroded and I suspect water was inside the points compartment.

I remove the 10 mm nut securing the ATU. There is a pile of white power inside the points compartment, significant corrosion of the aluminium case, rust on the points plate fasteners and evidence of abrasion on the DYNA III magnet attached to the cam of the ATU.

It looks like the lower screw of the left pickup is bent and there is aluminum shavings on it’s pickup. It has been rubbing on the rotating magnet.

Based on what I find, I decide to replace the DYNA III electronic ignition. I have some cleaning to do on the outside of the timing chest cover to remove the corrosion and return the finish to original condition.

Remove Alternator Wiring & Brushes

I note where the wires on the alternator go and remove them. Although I didn’t do it this time, putting labels on the wires to remind you where they go is a good idea.

Inspection of the alternator stator cover show that it was not mounted fully into the tabs on the timing chest cover.

I remove the alternator bushes from the bush holder. This makes it easier to remove the stator cover. There is a coil spring with an arm on one end the extends inside the rectangular hole for the brush. I use needle nose pliers to pull the leg out of the hole to relieve the pressure on the brush so I can pull the brush out of the hole.

Remove Diode Board

I remove the diode board which in my case requires cutting the tie wraps since the board has sheared of all four rubber mounts.

If the rubber mounts are intact, I would remove the four nuts that secure the diode board to the rubber mounts. You can see these nuts on this 1983 R100RS rubber mounted diode board.

Now I can detach the wires connected to the diode board. There is a wire on both sides of the board and two on the back of the board. The wire on the left side as you face the board goes to the “Y” connector on the alternator. The one on the right side as you face the board goes back through an opening in the timing chest cover and connects to a terminal on the starter solenoid on the top of the engine.

I remove the wires from the back of the board and the side wires from the alternator and starter solenoid. I label the ends of the wires in he engine wiring harness. Here is the diode board with the two side wires connected, the two ground wires connected on the back and the engine wiring harness.

Here is how the harness with the three phase wires is routed from the back of the diode board through the openings in the timing chest cover to the stator housing wiring block.

I remove the alternator 3-phase wiring harness and the condenser and rubber sleeve that protects the points wire.

Here is a short video showing the engine electrical wiring harness and how it routes inside the engine.

[VIDEO: CLICK TO RUN]

Here is the front of the timing chest cover with everything removed except the alternator.

Remove Alternator Cover, Stator and Disassemble

The stator cover was not installed flush with in the mounting ears. I’m not sure why.

I remove the stator cover by removing the three Allan head bolts.

I carefully pull the cover and stator as a unit off the mounting ears of the timing chest cover. Wires from the stator connect to terminals on the front of the stator cover and I don’t want to put strain on them. The stator wires are coated in shellac to insulate them and if the cover scratches them it can lead to short in the stator wiring.

With the stator removed, the alternator rotor mounted on the crankshaft nose is exposed. The large copper rings are the slip ring commutators. The brushes mounted on the stator cover rub on them to conduct DC power to the coil of wires in the rotor to create a magnetic field. As the rotor turns, the magnetic field causes AC electricity to flow in the stator wires, The AC current goes out the three wire connectors on the lower right side of the stator cover and into the diode board which changes the AC current to DC current to charge the battery.

I remove the nut, washer, spade terminal and the ring terminal attached to the “Y” connection on the front of the stator. Note the insulating washer around the “Y” screw post.

I remove the nut and flat washer securing the insulating washer on the “Y” terminal and then remove the insulating washer.

There is an insulating sleeve around the screw post and another insulating washer on the inside of the stator housing. I show how the insulators and screw post go together later as the same assembly is used on the “DF” terminal of the brush assembly.

I disconnect the spade terminal from the “DF” connector to the brushes by removing the nut, washer and spade terminal.

There is an insulating washer underneath the screw terminal of the “DF” connector.

I disconnect the nut, washer and spade terminal from the “D-” connector on the left side of the brush holder. This screw terminal does not have an insulating washer underneath it.

The screw terminals of the bush holder assembly are secured to the stator cover by a nut and washer inside the stator housing. These can be removed without removing the stator coil or the “Y” terminal stator wire. Since I’m replacing the stator, it’s easier to remove the 3-phase wires of the stator from the terminal block on the lower right side of the stator cover. I remove the 3-phase wires from the terminal block on the lower right of the stator cover by unsoldering the wires from the terminal block. It takes a good deal of heat so I use by 260 watt soldering gun.

Now I remove the stator from the stator cover.

Remove the Brushes

I use a 260 watt soldering iron to remove the brushes from the holder.

Compared to the new brushes, you can see how worn they are.

Remove the Brush Holder

I already removed the spade terminals from the brush assembly. Now that I can access the back of the stator cover, it’s easy to remove the nuts securing the brush holder.

The left mount is the “DF” terminal as shown by the insulator washer. Here is the hardware I removed.

And, here is the “D-” terminal on the right side hardware.

I remove the brush holder. This is a close up of the “DF” terminal showing the insulating washers, sleeve and mounting hardware.

Here is the stator cover with the various components that mount on it.

Remove Alternator Rotor

To remove the rotor I remove the Allen head rotor bolt. A regular socket will rotate the crankshaft so I use my cordless impact drill and put the socket adapter in the chuck along with the Allan bit and it backs right out.  If you don’t have a cordless impact drill, you can use an oil filter wrench to grasp the rotor while you loosen the rotor bolt. I who how I do that later when I use the rotor removal bolt to pull it off the taper on the crankshaft nose.

I use the BMW rotor removal bolt which is hardened so it won’t bend, thread it into the crankshaft nose until it bottoms out. I grasp the outside of the rotor with my oil filter wrench to keep it from turning while I tighten the bolt to pull the rotor off the crankshaft nose taper.

Here is the rotor, mounting bolt and the hardened rotor removal bolt.

With the rotor removed, the crankshaft nose is exposed. It’s a good idea to put some tape on it so it doesn’t get scratched while working. The taper needs to be clean and unmarked to hold the rotor securely.

Install New Brushes and Brush Holder

I cleaned up the brush holder and then soldered the new brushes to the holes in the metal plate. Before soldering the brushes, I replaced the rubber insulating sleeves that were on the original brush pigtails with shrink tube as the original ones had torn.

The holes had some solder still inside so I used a small drill bit to clean the solder out of them. I tinned the ends of the pigtails with solder before inserting them into the holes.

I install the brush holder being sure to install the insulators on the “DF” terminal mounting posts. Note that there are two insulating washers that mount on the front side of the mounting screw. I think this ensures the spade terminal is kept sufficiently far away from the stator cover to not short out when installing the wire connector.

Install New Stator

I cleaned up the stator housing, nuts, bolts, washers and the electrical connectors. For the electrical connectors I use copper polish and steel wool to remove the grunge and oxidation. The 3-phase wire terminal had some solder in the holes so I used a small drill bit to clean the holes out.

The new stator from Euro Motoelectrics has four wires; three are together on one side and are the 3-phase wires. The fourth has a ring terminal and goes to the “Y” terminal.

I route the 3=phase wires and the “Y” wire with the ring terminal from the back of the stator cover through the holes in the cover. Then I solder the 3-phase wires to the 3-phase terminal block.

The 3-phase wires have cloth insulating covers. Each of the three wires have a cover and there is a larger one around the three wires. Position the insulating covers on each wire so it extends to the edge of the 3-phase wire terminal block before you solder them to the 3-phase terminal block. They are hard to move once the wires are soldered to the terminal block.

I mount the 3-phase terminal block to the stator cover.

I make sure the insulators are installed on the “Y” teminal posts and then insert it through the stator cover.

Note that there are two insulating washers that mount on the front side of the mounting screw. I think this ensures the spade terminal is kept sufficiently far away from the stator cover to not short out when installing the wire connector.

Here is the stator cover with the stator mounted to it along with the other parts and pieces.

The Euro Motoelectrics kit comes with a set of the other wires needed for the engine electrical components.

The top black wire goes on the diode board left side terminal and the “Y” spade connector on the alternator cover. The next wire down with the red end goes on the diode board right terminal and to the starter solenoid post that includes the (+) battery terminal. The bottom cable with the three wires, black, green and red, is the 3-phase wires that go from the back of the diode board to the 3-phase terminal block on the lower right side of the alternator cover. The vertical red wire is a ground wire for use with rubber mounted diode boards. I don’t use it since I replaced those with solid metal mounts for the board. I’d recommend removing the rubber mounts as this was not a good idea by BMW.

Install (+) Battery Wire on Starter Solenoid

I am replacing the (+) battery wire. The ring terminals have different size holes and the larger one on the black end of the cable goes on the stater solenoid threaded terminal and the red covered end with the tag goes on the battery terminal

The old one has a circular kink formed in it so I bend the new one in a similar way before installing it.

I got a new “D” shaped grommet to fit on the (+) battery cable. It fits into the rear “D” slot of the timing chest cover. The center is solid so I use a utility knife to make a slit in it so I can slip on the end of the battery cable.

I install the battery cable on the threaded terminal of the starter solenoid and position the “D” grommet in the timing chest cover.

Install “Red” Wire on Stater Solenoid

Next, I shape the “red” wire and put the ring terminal on the starter solenoid threaded terminal on top of the (+) battery cable. I route the wire through the center hole in the timing chest cover so the connector is on the right side of where the diode board will mount.

Install Front Engine Harness and Diode Board

I mount the front engine harness in the timing chest cover so I can route the black wire to the spade terminal on the starter solenoid.

Now I put some dielectric grease on the terminals on the back of the diode board the blue wire (either of the left side terminals) and the 3-phase wires (right side terminals) plug into.

I route the 3-phase wire bundle through the center hole of the timing chest cover and back out the lower right side hole.

I put dielectric grease on the diode board right spade and plug the “red” wire from the solenoid spade terminal on it. Then I plug in the 3-phase wires on the back of the diode board. The order of the 3-phase wires is not important.

Now I mount the diode board on the metal mounting studs. It’s a tight fit and I have to wiggle it quite a bit to get it onto the four studs.

Install Black Wire To Diode Board Left Spade and Alternator “Y” Spade

The black wire connects between the left side diode board spade terminal and the lower left “Y” spade terminal on the alternator cover.

I put dielectric grease on both spade terminals and push the wire on to them. The 90 degree spade on the wire goes on the left side diode board spade.

Now I install the washers and locking nuts of the diode board mount to secure the board to the timing chest cover.

Check Wire Routing To Avoid Rubbing on Metal Edges

The plastic sleeve on the 3-phase wire bundle should be positioned so it protects the wires from chaffing on the edge of the hole in the timing chest cover.

I test fit the top engine cover to be sure the batery (+) cable will not rub on it. It’s a tight fit.

I check the diode board left side “Red” wire to be sure it doesn’t touch the hole in the timing chest cover, the starter motor, and the engine breather pipe. I have to do some pushing, shoving and bending to keep it off all these contact areas.

Install New Alternator Rotor

The procedure for the R100RS is the same as the R75/6.

• 11 BMW 1975 R75/6 Replace Timing Chain, Crankshaft Sprocket, Nose Bearing:  Install New Alternator Rotor

When I had to remove the rotor on the R75/6, I couldn’t get the BMW rotor puller bolt to thread into it. But, when I tried to extract the rotor for the R100RS, the BMW rotor puller bolt worked. Perhaps there has been a change in the threads used in the Euro Motoelectrics rotor?  If so, that’s a good change in the design.

Be sure to thoroughly clean both the crankshaft taper and the inside of the alternator rotor with alcohol wipes until they are clean. As you can see, the rotor taper is pretty dirty out of the box.

I put a drop of oil on the outside of the taper so when I insert the rotor it will slide easily though the oil seal and not nick the seal edge.

Rather than use a screw driver against the stator housing mounting ears and risking damage to them, I use the oil filter wrench. I think this method is safer.

Install Alternator Stator and Housing

The installation is the same for the R100RS as for the R75/6.

• 11 BMW 1975 R75/6 Replace Timing Chain, Crankshaft Sprocket, Nose Bearing: Install Alternator Cover and Wiring

Since I found that the original alternator stator was not mounted evenly in the ears of the timing chest cover, I make sure the new one does. If not, then one or more of the ears maybe bent.

I put some dielectric grease on the electrical connections of the alternator cover and install the “Y”, brush pickup and 3-phase wires.

Here is the front of the engine with all the wiring and engine electrical components installed except for the new Dyan III electronic ignition. The link at the beginning of this write-up includes one to the Dyna III installation.