I decided to replace the stock 240 watt charging system with a 400 watt charging system available from Euro MotoElectrics (EME); the EDL III kit for the 107 mm diameter stator cover. This alternator uses the same Bosch design with an electromagnetic rotor. The bike is being converted into an RT and will have heated grips and I plan to use the auxiliary power socket for a heated vest, so an increase in alternator output is warranted. And as icing on the cake, I’ve not installed this kit before, so I get to learn something new. 🙂

The EME Type III kit comes with an adjustable electronic voltage regulator. I usually install the voltage regulator when I’m ready to install the main wiring harness, so I don’t show how to install it in this write-up.

Resources

I’ve installed the stock alternator on my 1977 R100RS project. You will find that the procedure for the EME Type III 400 watt alternator is very similar with the exception of the connections on the diode board.

• 12 BMW 1977 R100RS Replace Engine Electrical Components

And here is the link to how I removed the stock Bosch alternator.

• 12 BMW 1983 R100RS Remove Diode Board, Alternator & Electronic Ignition Sensor

Parts

I purchased all the parts from Euro MotoElectrics. In addition to the Type III, 107 mm charging kit, I purchased the BOALT-HAR80 wiring kit which is for the R80 models. EME sells a similar kit for the R100 bikes, BOALT-HAR100,  but I only needed the voltage regulator sub-harness, (part# 61 11 1 243 646) which is both kits. There are a few more wires in the R100 kit that are already in the Type III charging system kit, but they are duplicates.

In the table below, I show BMW part numbers for the wires and the EME kit that includes them.

Part #	Description	Qty
EDL3-ALTKIT107	EME Alternator Kit,  400 watt Type III	1
BOALT-StatFram107Plus	EME Stator Cover+All Hardware	1
BOALT-HAR80	EME ALTERNATOR WIRE HARNESS KIT	1
61 12 1 243 216	BATTERY CABLE (PLUS POLE) (from 09/78) In EME BCK-475216	1
12 32 1 243 178	WIRING SET, Alternator 3-Phase Wires, In EME EDL3-ALTKIT107 & BOALT-HAR80	1
12 33 1 357 639	WIRING SET, Alternator “Y” Wire, In EME EDL3-ALTKIT107  & BOALT-HAR80	1
61 12 1 243 224	WIRE CHARGING CURRENT, DB DC Output, In EME EDL3-ALTKIT107  & BOALT-HAR80	1
61 11 1 243 646	ENGINE WIRING HARNESS (from 09/80) In EME BOALT-HAR80	1

Special Tools

These are the special tools needed to do this work beyond the typical wrenches, screw drivers and socket wrenches most people have in their tool box.

Soldering Iron

I have to solder the three alternator AC phase wires to the terminal strip on the front of the stator cover.

The stock BMW stator requires soldering the alternator brush wires to the terminals. I decided to replace the original stator cover with the EME stator cover “Plus”. The “Plus” version of the EME stator cover includes screw terminals for the alternator brush wires. EME also sells new brushes with ring terminals. So when the brushes need replacing, I can quickly change them without de-soldering and soldering them on.

NOTE:
BMW no longer sells the stator cover, part# 12 31 1 243 002, separately, but only as part of a complete alternator assembly. The EME stator cover “Plus” includes all the other parts attached to the stator cover at a price less than purchasing only the brush holders from BMW. 

Spin On Oil Filter Wrench

I like to use one of these to immobilize the rotor when I torque the rotor bolt.

Video

This video summarizes the installation procedure.

VIDEO: 1983 BMW R100RS Install Euro MotoElectrics 400 Watt Charging System

Preparation

There are several things I need to do to prepare the parts before I install them.

Clean Crankshaft and Rotor Tapers

The rotor and the crankshaft nose have precision machined tapers. The interference fit between them is what keeps the rotor from spinning on the crankshaft nose. The rotor bolt is not the primary method of preventing the rotor from spinning on the nose, its the taper interference fit. Consequently, for this to work, both tapers have to absolutely clean and completely free of any oil, even finger print oil.

WARNING:
If the rotor spins on the crankshaft taper, it will damage the crankshaft. You MUST be sure the interference fit secures the rotor on the crankshaft as I show later.

I had put masking tape on the crankshaft taper to protect it from getting scratched when I was using the Cycle Works tools. When I remove the tape, there is adhesive left behind. I use some lacquer thinner to remove the adhesive on the crankshaft taper and also on the taper inside of the rotor to remove any deposits left over from machining it. Then I use alcohol wipes to clean the two tapers.

NOTE:
Later on, you will see that I did not get the tapers absolutely clean using lacquer thinner and alcohol wipes. Based on that, I recommend using brake cleaner on the crankshaft and rotor tapers to ensure you get all oil and contaminants off them.

Clean Starter Solenoid Terminal & Ground Wire Octopus Terminals

I use some metal clean to remove tarnish and deposits from these terminals.

Clean Rotor Slip Rings

I use metal polish on the rotor slip rings to make them shine. There is some grunge on them, which is to be expected.

Crimp Spade Terminals As Required

I like the female spade terminal to be tight on the male terminal. So I test fit all the spade terminals to see how tight the fit is. If any feel a bit loose, I use a pair of narrow needle nose pliers and slip one jaw inside the plastic cover against the edge of the rolled over edge of the spade terminal and the other jaw on the outside of the cover and squeeze the rounded end to compress them enough that they go on tightly. I repeat on the other rolled over edge. I repeat as needed until I get a nice tight fit.

Plug Second Grommet Hole in Voltage Regulator Sub-harness

There are two grommets in the top of the inner timing cover. The rear one has two holes, one of the battery (+) cable and the cable from the bean can (points) that goes to the ignition control unit. But, the front grommet only has one cable, the voltage regulator sub-harness. At one time, there were two styles of grommet, the rear with two holes and the front with one. Today, it looks like only the two hole version is available. The empty hole on the front grommet can let water into the front of the inner timing cover housing. I put some Ultra Black RTV into the hole to plug it.

Install Stator Wires On Stator Cover Terminals

The stator coil has four wire leads as shown in the picture below. The “Y” terminal, or center tap wire, has a ring terminal soldered on it while the other three wires are bare. The three bare wires are the three AC output phases of the stator. I solder them onto a solder pad on the stator front cover.

The “Y” wire ring terminal fits on a bolt in the stator cover and is secured with a lock washer and top nut. The bolt is secured with a bottom nut against the cover.

Before installing the cover on the stator coil, I want to tighten the bottom nut on the bolt so it is tight to keep the bolt from spinning when I tighten the top nut to secure the “Y” wire ring terminal. I remove the top nut, lock washer and spade terminal from the bolt.

WARNING:
The bottom nut is on top of an insulating washer. Do not tighten it so much that you fracture the washer. If the washer is broken it may not insulate the “Y” wire from the stator cover. Since the stator cover is grounded, this would short out the stator coil.

After tightening up the bottom nut, I stick the wires through the holes in the cover, as shown in the picture below.

Then, I install the spade terminal on top of the bottom nut, then the “Y” wire ring terminal, the lock washer and finally the nut.  I tighten the nut until the “Y” wire ring terminal is securely fastened.

The three AC phase wires have white insulation over them that can be moved along the wires. I test fit the three AC phase wires through the cover, and adjust the insulation so that it will be very close to the edge of the solder pad so they will protect the leads from being shorted.

After I get the insulation adjusted,I bend each wire 90 degrees and fit it into a slot in the solder pad. Then I use my solder gun and solder the leads to the solder pad.

NOTE:
You can put any wire in any of the three slots, it does not matter which goes where. That said, I arrange the wires after they are through the hole so they aren’t twisted around each other so there is minimal strain on the wires.

After I soldered the three AC phase wires, I use my diagonal wire cutters to trim the excess wire.

Here is the stator with the stator wires attached to the terminals on the front cover.

Install Ground Wire “Octopus”

NOTE:
This bike had the ground wire “Octopus”, but I don’t know for sure if this is standard for this year and model. There are ground wires in the EME kit. If you don’t have ground wires, I would install them on the metal studs, or if you have the rubber diode board mounts and decide to keep them, install them on the back side of the stud hole in the diode board to ensure it is grounded. That said, I believe the original rubber diode board mounts cause problems and are not the solution to the diode board problems BMW was trying to solve back in the day.

This is the ground wire “octopus” that I found.

There are different size ring terminals on the wires. The larger terminal goes under the 6 mm bolt that secures the starter motor bracket on the engine block.

The two longer leads with the small ring terminal fit over the studs of the metal mounts. I put these on the top studs. The last lead fits under a bolt in the center of the inner timing cover that I show later.

There are also two stock BMW ground wires. I put those on the bottom studs and connect them to the center bolt.

Here are all the ground wires installed. Each stud has a wire and the octopus is attached to two different bolts. With this level of “belt and suspenders”, the diode board should always have a good ground.

NOTE:
Indeed, this is a belt-suspenders-tape level of insurance 🙂  You don’t have to go this far, but this is what came with the bike, so I might as well use it.

Install Voltage Regulator Sub-harness and Diode Board

I install the grommet of the voltage regulator sub-harness into the front slot on the top of the inner timing cover.

There are two short wires toward the top; one is BLUE and the other is BLACK.

The BLACK one goes on the spade terminal of the starter solenoid, so I route it through the center hole in the inner timing cover.

Before I attach it to the spade terminal, I put some dielectric grease on the male spade to prevent corrosion. There is a packet of it in the charging system kit, but I have an “industrial” size tube that I need to use up. 🙂 I will apply dielectric grease to all the spade terminal connections.

The BLUE one goes on the back of the diode board on the “D+” terminal.

Once the BLACK and BLUE wires are attached, I mount the diode board on the four metal studs and secure it with a flat washer and lock nut on each stud. I tighten the nuts but I don’t get too aggressive since the diode board is made of phenolic and I don’t want to crack it.

Install Rotor

The taper on the end of the crankshaft nose and the inside of the rotor MUST be completely free of any oil or debris. I explained earlier how to clean them correctly.

The journal on the end of the rotor with the tapered hole fits into the front main seal to create an oil tight seal. I put some oil on it to ease it past the seal and prevent damage to the seal when I install the rotor. I’m careful not to get any oil on the taper inside the rotor shaft.

I carefully slide the rotor onto the crankshaft taper until it is on all the way. I use a rubber mallet and tap squarely on the end of the rotor two times to seat the interference fit.

Then I grab the rotor and twist it. It should not slip or come off the taper if the interference fit is clean and tight and I should be able to turn the crankshaft as I turn the rotor. BUT, it did slip on the nose and came right off in my hand.

I clean the tapers again, but this time with brake cleaner on a clean blue shop towel. I repeat the interference fit test and now I can spin the crankshaft without the rotor slipping so the interference fit is working as it should.

I install the rotor bolt. There are two sets of threads, one in the rotor and the other in the crankshaft nose. When the bolt threads through the rotor it will slide further until it can engage the threads in the crankshaft nose.

The rotor bolt torque is 14 FOOT-Lbs which is fairly low for my foot-pound torque wrench. So I use my INCH-Lbs wrench set to 170 INCH-Lbs (2 INCH-Lbs more than 14 Ft-Lbs, but whats a couple INCH-Lbs among friends 🙂 ). I immobilize the rotor using a spin-on oil filter strap wrench tightened around the steel fingers of the rotor while I torque the rotor nut.

WARNING:
Do not misread the above and by mistake try to torque the rotor bolt to 170 FT-Lbs. Obviously this will strip the bolt and damage the crankshaft.

NOTE:
The rotor nut keeps pressure on the interference fit of the tapers, but it DOES NOT prevent the rotor from slipping on the crankshaft if there is any oil or debris on the tapers and the interference fit test failed. If the rotor slips, it will damage the crankshaft.

Install Stator with Stator Cover

As I mentioned in the Preparation section above, I like to dress and clean the three sleeves on the front of the inner timing cover that the stator housing slides into to remove any burrs and debris so the stator cover will slide smoothly into the sleeve.

I align the stator cover bolt hole with the slot in the stator housing.

I’m careful not to nick the stator wire insulation as I mount the stator over the rotor and up against the stator housing sleeve in the inner timing cover.

I need to slide the brushes over the slip rings and if the coil spring is pushing them, it’s hard to slide the brushes and it’s easy to damage them on the edge of the slip rings. So I pull each of the two coil spring fingers that push the brushes down on the slip rings and put the fingers on the edge of the spring holder. This takes the pressure off the brushes so I can push them up inside the brush holders.

After I slide the stator coil over the rotor, I align the stator cover so the hole in the cover and the slot in the stator housing line up with the hole in the inner timing cover.

I install the three stator cover bolts with wave washers in the holes in the inner timing cover. If the cover and stator housing are aligned properly, I can easily screw the Allan bolts in by hand. If there is resistance to screwing in a bolt, I jiggle the cover to remove the misalignment.

I use an Allan socket to snug up the Allan bolts by hand without a socket wrench. Then, I go around and hand tighten each bolt about 1/2 – 1 turn in sequence to draw the stator housing uniformly into the three inner timing cover sleeves. I continue until the edge of the red band on the stator housing is uniformly flush with the edge of the three sleeves in the inner timing cover.

Finally, I tighten the bolts until cover feels tight in the sleeves. These are 5 mm bolts so I choke up on the socket handle to keep from over tightening the bolts and stripping the threads or cracking the stator cover castings. The stator is installed.

Install Final Wiring

I’m ready to install the wires that connect the diode board to the starter solenoid, the diode board to the stator cover, and the alternator brushes to the voltage regulator sub-harness.

Connect Diode Board DC Output Wire To Starter Solenoid

The DC output of the diode board charges the battery via the battery (+) terminal. The diode board terminal on the right edge is the DC output from the diode board. The wire I decided to use comes from the BOALT-HAR80 wiring kit. It has a ring terminal on one end and a large female spade terminal on the other that fits the larger DC output terminal on the diode board.

I bend the ring terminal so it is at 90 degrees to the wire so it will fit into the limited available space around the starter solenoid screw terminal.

I route the B+ wire over the crankcase breather hose and then attach the ring terminal onto the stater solenoid screw terminal.

I route the other end of the B+ wire with the spade terminal through the hole on the left side of the inner timing cover as shown in the picture below so it will come out in the front of the engine next to the diode board DC output terminal.

I apply some dielectric grease to the diode board spade terminal and attach the B+ wire spade terminal to the larger spade terminal (there are two other smaller ones as well).

Connect Battery (+) Cable To Starter Solenoid

I install the new battery (+) cable on the starter solenoid screw terminal. I orient the ring terminal of the B+ cable from the diode board so the wire clears the hose clamp on the crankcase breather hose so it won’t chafe on the hose clamp. Then I install the lock washer, nut and tighten the nut. Finally, I put some dielectric grease on the nut and ring terminals to help avoid corrosion.

I put a loop in the Battery (+) cable so it will align with the slot in the back of the inner timing cover as shown in the picture below. The Battery (+) cable will fit in a two-hole rubber grommet that I will install later.

Install Stator to Diode Board Wires

There are two wires that connect the diode board terminals to terminals on the stator cover; the he bundle of three AC phase wires and the YELLOW “Y” wire.

The terminals on the front of the diode board are labeled, left to right, “U”, “Y”, “V”, and “W”.

Before I install these wires, I put dielectric grease on all the spade terminals on the diode board and the stator cover.

I attach the YELLOW “Y” wire to the “Y” terminal on the diode board and the “Y” terminal on the stator cover.

I install the bundle of three AC phase wires on the remaining terminals of the diode board and the terminals on the solder pad of the stator cover. There is no order so these wires can go on any terminal.

I connect the BLACK and BROWN wires of the voltage regulator sub-harness to the brush spade terminals on the stator cover. The BLACK wire goes on the right (DF) terminal which has the insulating washer and the BROWN wire goes on the left (D-) terminal which has no washer.

I orient the woven sleeve over the three AC phase wires next to the stator cover.

I make sure the brush wires from the voltage regulator sub-harness are in front of the bundle of three AC phase wires.

The charging system is installed.

Install Voltage Regulator

The voltage regulator is installed on a bracket on the right side of the frame. I previously replaced the stock voltage regulator with an adjustable electronic one from EME. There is a white adjuster on the bottom of the regulator that can be used to adjust the maximum voltage from the alternator to the battery. As supplied, the setting is usually correct for AGM or lead-acid batteries.

I attached the regulator to the frame with two Allen bolts and wave washers and then plug in the triangular plug into the bottom of the regulator.

Revisions

2020-07-26  Added Voltage Regulator section.