Don’t Eff With Electricity, Man

My R90S is, I am ecstatic to say, back on the road.

At the risk of further offending the motorcycle Gods, who have already demonstrated in no uncertain terms that they have both the tools and desire to use them to punish moto-hubris, the bike is running even better than it did before its little tussle with electricity.

A top gear blast up MD17 this a.m. had it pulling top gear with an authority that is downright shocking for a motorcycle of this age.

Folks may recall that when I found myself beside the road with a mass of smoking wiring, I briefly considered whether, had I been on a roadside in Tibet, I would have been able to effect repairs in-situ to save my own life.

Subsequent developments have illustrated that had this been the case, I would have made a lovely chewy snack for the Snow Leopards, and someone would have discovered my frozen bones come springtime.

This perhaps requires some further explanation.


I’ll admit that when I first got the bike back to its position beside the workbench in my garage, I had no desire to leap feetfirst into what I suspected was going to be a depressingly large and complex repair. The fact that much of the repair work needed to occur inside the confines of a badly lit 7 inch diameter headlamp shell working on tiny components wasn’t doing much for my enthusiasm.

So after a trip to the house of Manny, Moe and Jack to gather all of the things I knew would be required to repair existing or fabricate new wiring harnesses — flag connectors, heat shrink tubing, and several colors and gauges of primary wire — what became most important was to quiet my mind and achieve the inner peace required to remain calm and mindful in the battle that was to come.


Ordinarily, when any bit of mechanical kit belonging to me blows springs, I become temporarily insane.

This assumes, of course, that one believes I am not permanently so, but I digress.

The ‘I cannot rest until I fix it’ fugue state involves a sort of mono-mania. My mind at rest becomes filled with schematics and engineering diagrams. Where there might ordinarily be thoughts of poetry there are checklists of repair parts and UPS ship tracking data. More complex problems that don’t yield immediately to diagnosis manifest themselves in dreams. I become nervous and jerky, furtive, distracted.

I have, obviously, a more than understanding spouse.

It’s easy to understand why one wouldn’t want to welcome this state of being with open arms.

So I did what any self-aware, mature and responsible person would have done under the circumstances.

I embraced denial.

This, frankly, required all of the effort and self-control of which I am capable.

For 10 days, I didn’t go in the garage.

Other people had to take up the slack with taking out the garbage and the recycling.

The beer fridge sits on the end of the workbench next to where the S was waiting, so for those days we inhabited the Oat-Soda-Free-Zone.

Then, after those days of introspection and purification, I was ready.


One of my favorite new tech tools is an LED-based worklight. It looks exactly like the Halogen worklights of old, but is superior in a couple of major ways.

First, it generates absolutely no heat. Compared with halogen tubes of yore, which ran hot enough to be a source of ignition, and threw enough heat to limit their use in close to a work item, these lights can be placed wherever required — no matter how goofy — without any discomfort or hazard.

I set up a comfortable work area directly in front of the S. I positioned an old-fashioned 33 gallon galvanized steel trash can to my left. I have a field electronics repair bench made of a curved and tapered piece of 3/4 in plywood that I fabricated and used to great effect during the construction of my teardrop camper. The shape and taper allows it to be positioned in confined spaces to support the work during crimping and soldering. I placed the field bench atop the can and positioned my soldering iron, linemans pliers, primary wire assortment, connectors and heat shrink tubing where they were conveniently within reach. I also borrowed a camping chair of Doris’ that she uses for Plein Air painting — it’s a basic canvas folding directors chair but with an important twist — it has a 1 foot by 2 foot table that pivots up from the frame and locks into place on the right side of the chair.

With all of the tools, materials and shop manuals/wiring diagrams at the ready, I took a deep, cleansing breath, and began the work.


Anything that had been connected to the ignition switch had been effectively vaporized. I took a few pictures with my phone, made a few notes, and removed the switch connectors one at a time — fabricating replacements with the appropriate gauge, color and connector types. The main hot wire which carries juice from the switch to the rest of the bike — ignition, etc — was originally a 14 gauge wire — I replaced it with a heavier 12.

Some conductors that were not connected to the switch were also damaged. Ones where the wires were still ductile I reinsulated with heat shrink tubing. Where the wires had been mechanically or electrically compromised, I cut the damage out and spliced and replaced the damaged areas — insulating both the splices and new connectors with heat shrink.

All told, this portion of the work was proceeding far more smoothly than my initial anxiety had indicated. After a few sessions of 40 to 90 minutes, everything in the headlamp shell that had been damaged had been repaired or replaced. It was time to see if it was going to be that easy.


It wasn’t, of course.

I reconnected the battery, although I didn’t crank the negative terminal down given the statistical possibility I might have to remove it again in a hurry. The dashboard clock started. No explosions of smoke occurred.

I turned the key. The dashboard lights came on.

I pressed the starter. The right cylinder fired. I went to roll the throttle open slightly, as this bike does require slight throttle to start.

The throttle wouldn’t move. I heard a slight arc. I kill switched it and turned off the key and disconnected the battery.


My workbench has a holding fixture made of 4×4 that is used to support airhead tanks. The fixture allows me to place the tanks on the bench without having any weight resting on the fuel petcocks. I pulled the saddle and tank and placed the tank on the bench.

Upon returning to the bike, it became clear that the switch wasn’t the only return address for electrical havoc.

Sitting on the left side of the frame backbone is the Starter Protection Relay. The relay, in the /5 and /6 motorcycles sits in the middle of the positive power bus that energizes the entire motorcycle. The connections to the starter protection relay were all roasted — the relay itself has a masonite bottom which is sealed with vinyl — most of the vinyl had melted as well.

Trouble radiated outward from there.

The multiple layers of protection on the tachometer drive cable — a mechanical linkage in these bikes — both the cable jacket and a second layer of vinyl protective sleeve, were vaporized. It looked, to my eyes, like during the earliest stages of ‘the event’, that the relay had overheated, then melted through the tach cable — which then provided another route of conductivity — and the trouble kept going from there.

It was clear where the tach cable had touched the throttle cables — there were burn marks on their jackets as well, showing exposed metal sleeving. It was clear why my throttle wouldn’t open — the cables were welded internally to their jackets inside the cable.

My R90S does have a few non-standard performance modifications. One of the most important ones is an on-handlebar brake master cylinder to replace the weird alice cable operated under-tank unit that was stock on these motorcycles. Where the original master cylinder and brake light sensor sat, there is a hydraulic junction which uses the original sensor and wiring.

Although the dealer that sold these kits advertised them as a stainless steel brake line and master cylinder upgrade kit, for reasons I’ve never understood, they supplied a OEM-type rubber line to connect the master cylinder to the junction. Using rubber in this application turned the stainless steel lines that went to the calipers from performance kit into dress-up parts, as the resistance to expansion under pressure that steel provides was negated by an expanding rubber line upstream.

During the dance of the electrons, that rubber brake line had picked up a nearly dime sized deep burn. Although the front brakes were still working, the first time I was hard on the brakes entering an 80 mph corner that burn was simply my death waiting to happen. I’d need to obtain a replacement brake line.

Seeing how severe some of the second layer of damage was, I knew I needed to take a deeper look. After a brief peruse of the wiring diagram, I pulled the alternator and starter covers of the motor.

I’m so glad I did.

The wires coming off the starter relay go to the diode board and starter solenoid.

Those wires, as well, were in bad enough shape to warrant replacement.

The main wiring harness of the motorcycle, thankfully, didn’t show any signs of heat distress. These harnesses are not easily or affordably located any more, so it was some solace that I wasn’t going to need to snipe hunt up one of those.

I did have quite a list of things I was going to need though, so I cleaned up my work space, closed the garage doors, and took to my computer to locate and buy the next layer of parts I was going to need.


First order of business was the list of things that only the dealership network was going to be able to supply. A few moments with the online fische, and a new tach cable, set of throttle cables and the associated cable boots — which these days seem to have a life expectancy of about 4 months — were on the way. A few seconds of further contemplation added a complete set of headlight retaining springs — remember how this all started? — to the mix.

That was just the beginning.

Remember that the connectors on my diode board looked like they came from Salvador Dali Engineering? Stories, now suspect, relate diode boards that were reduced to useless slag by having a front engine cover graze by them while the main battery ground was still connected.

Surely mine was slagged, right?

My bike also has a period hot rod part in the form of what was then called an ignition booster. The ignition booster essentially uses the original ignition points as a low voltage switch and then puts the dwell and condenser functions into solid state stuff where the spark peak and duration is stronger and better controlled.

Of course, the unit sits right next to the melted relay and right between the Dali Rectifier and the melty stuff coming off the starter solenoid.

Given how my luck had been trending recently, I didn’t feel great about the likelihood this unit was not an ex-parrot.

I’m the sort of tech that wants to have every single part I’m going to need right at hand when I start a job. Now purchasing both a replacement diode board and ignition booster are easy, but throwing $200 at a problem I wasn’t sure I had seemed too much to appease my inner mental person.

My buddy Al, who knows a little about airheads, dropped by the garage and examined the patient, dropping a few “Hmmmmms” and “I sees”.

After consultation with Al, I resolved to fix everything we were sure was roasted — the folks at Euro Moto Electrics had a better than OEM quality engine electrics harness — and then see if these antique electronics still actually worked.

If they didn’t, replacements were just 2 Franklins and another 2 days away. I’d survive another two days, if need be.


I just didn’t like the look of my ignition switch.

While the switch was working, It had some sort of lube dripping visibly from the rear of the housing. The base of the switch, which I believe is Bakelite, was loose on the back of the lock housing — moving visibly.

It has been the one component that had taken the biggest blast of a dead short.

It was not the sort of thing you wanted to have to wonder about when running in the meat of top gear.


BMW motorcycle dealers cannot get you this switch.

BMW Mobile Tradition, the business unit set up to make sure you can get classic motorcycle parts that the dealers cannot get for you, cannot get you this switch.

Even the small population of European suppliers of ‘pattern parts’ don’t have this switch, or even reasonable facsimile thereof.

So I would need to find a used part.

Al had recommended Larry “Stoner” Stonestreet — owner of an independent California BMW shop.

Stoner was able to supply a fairly good condition used switch, and at a fairly reasonable price, especially considering the supply/demand thing.

I would need to find a skilled or adventurous locksmith, later, but was trying to break the overall problem down into single, bite size pieces.

That was going to be a different mouthful.


I didn’t really like the look of my headlight ring, either, come to think of it.

In the entire time I’d had the bike, it had always been kinda flaky.

My bike was an early 1975 — and it had the /5 type spring retaining clip at the bottom of the headlight ring. It had always had a propensity for not fitting as deterministically as I’d prefer — and either popping lose or rotating on the headlight.

BMW, of course, had redesigned the part to use a screw driven clamp, which pointed the way to he possibility that mine was not the only one that behaved less than admirably.

Add to its list of sins that this one had spit the spring that nearly incinerated the bike and one can understand why I might not have fond or confident feelings about it.

The nice folks at Wunderlich had an OEM quality part of the new design for almost half what the dealers were asking, so we PayPaled up on of those.


When the next group of packages were received and arranged on the workbench, I went back down for another dive.

I pulled the fairly crispy tach cable — it broke in half during removal — and replaced it with a new one and its matching rubber engine grommet.

The throttle cables were next. During the miniature spring wrestling match that is installing new cables in a DelOrto carb, one of the needle retaining clips popped loose. I quickly checked a few technical sources to see where it was supposed to be.

“Third from the top of four grooves.”

My needles have three, of course.

I went with the center groove. If I proved to be wrong, it would take 10 minutes to set right.

The wires on the rectifier and starter solenoid were replaced — the new ones all looked like they were one wire gauge heavier than the ones which had failed.

After everything was connected, I reconnected the battery and — using the old switch — turned the key. I checked the basic systems of the bike — no smoke leakage and everything I could test — turn signals, brake lights, horn — all appeared to be working. I quickly tested the starter and it spun over.

So I replaced the fuel tank, reattached the fuel lines and wished there was some sort of approved entreaty to a motorcycle deity.

I set the choke, pressed the starter and waited through what seemed like way too many compression strokes.

“Easy, mate. The fuel system had been dry, the carbs have been apart, it’s going to take some time to get the jets primed, it’s just going to take a bit longer….”

At this point, the left cylinder fired, and engine stumbled to life, then took throttle cleanly and revved. The alternator light went out, and the voltimeter swung reassuringly and deterministically to the right — a nice solid 14.2 volts.

We might not be there yet, but this was going to be all right.


With things coming back together, I needed to source and install a brake line for my suspect burned one.

Since this application was a non-stock one, I was resigned to contacting the dealer from whom I’d originally purchased the upgrade kit, figuring that was the path of least resistance. I called them on the phone to discuss it several times without success. I’d either be placed on hold and then dumped to voice mail or get routed straight to voice mail. Having left messages twice without a return phone call I concluded this was another sign from the MotoGods that said entity was neither interested in either me or my little problem.

The guys at Adventure Rider had, as always, the solution. They fingered Bud Provin, a very skilled tech that had formerly worked in my area, and his business, The Nickwackett Garage, as the best source for any kind of custom stainless steel brake or clutch lines. I shot Bud an email, and, true to his ADV-reputation, he knew the kit, the dimensions, and fabbed and shipped exactly what I needed within about 2 hours of the initial contact. Heck, as a former customer, Bud even shipped it before I’d made payment arrangements.

In a world filled with distrust, assholes and hacks, both Bud and his work stand out as examples of integrity and sterling craft.

At lunchtime the next day, I met the mailman coming up the driveway and took the box directly to the workbench.

Bud’s stainless steel line was a nice an example as I’d ever seen — small diameter, beautiful fittings, and a unique setup for rotating and positioning the main banjo fitting for the master cylinder connection. The entire stainless steel line between fittings was covered in a transparent vinyl jacket to keep the braided line from buzz-sawing anything it might rest against.

After about 20 minutes with the 12 and 13 mm box end wrenches from the bike’s stock tool kit, and my trusty 7 liter hand pumped beast of a MityVac fluid evacuator, the new line was in place. I could tell, even before any road test, that with the reduced line volume and expansion, that power and feel from the antique single piston brake calipers was markedly improved.



The next order of business was to get a trustworthy ignition switch installed. It would be better still if I could get it rekeyed so it matched my steering stem and saddle locks.

With my replacement used switch in hand, I started calling locksmiths around Frederick. Telling a shaggy dog story about an old german motorcycle, a fire and an oddball lock scared a few off them off. After a few calls, though, we had a live one.

The guys at Able Locksmiths are motorcycle enthusiasts, and they were able to develop a plan on the fly.

“Pull the damaged switch from the bike and bring both it and the new one up to the shop. We can use the burned switch to figure out how it works — its expendable — and as a source of lock wafers or mechanism if we need it.”

As a plan, it seemed pretty solid, so I pulled the suspect switch, threw the ziplock bag of parts into my topcase of my K bike, and scooted off for Frederick.

The guys at Able were better than their plan.

The smith that drew my job took the old switch and placed it on a no-rebound work mat. This work surface had little miniature trays to organize tiny parts and long rubber fingers that ensured that work stayed where one placed it, and if parts flew loose, they would be arrested and kept from bouncing free. The Smith had the old switch disassembled in 3 minutes or so — immediately lit up with a smile and then went after the good one. While he was working he talked with me about the 1947 HD Servi-Car he rode, and the Ural sidecar rig he planned to buy. Anybody that scores this consistently high on the Moto-wierdness scale is completely cool by me.

After 10 minutes, the undamaged lock of my burned switch had been transplanted to the new switch, and I was $15 dollars lighter and back up the road towards the garage.

After 10 minutes or so in the garage, the hybrid repaired switch was back in the bike and functioning perfectly.


A confident man might have begun thinking that we were in the home stretch of this job.

When it comes to vehicular electrical work, I am not a confident man.

I started out by looking for some good quality restoration pictures of BMW electrical systems of similar vintage. As they did many times during this job, my fellow inmates at Adventure Rider were able to shed light on what needed to be done. Factory and factory quality wiring had some qualities that were notably missing from my headlamp shell.

All of the harnesses that enter the shell are — in stock condition — routed around the outside of the shell and held in place with ductile metal clamps that are provided for that purpose. The connections to the circuit card which forms the core of the electrical system are the achieved by fanning out the individual connections from the harnesses and fastening them to numbered and color coded connections on the card. This arrangement makes all of the headlamp wiring easier to access and repair, but also opens up a needed void space in the center of the headlamp shell, and ensures that the headlamp wiring and associated connections are not pressed into the rear of the headlamp assembly.

In my case, where a non-stock LED headlamp’s heatsink needed about a half an inch of additional clearance, this arrangement was even more important. It is possible that some ‘negative clearance’ had helped the significant errant spring in its errant springing that had started the whole unseemly chain of events.

So I spent some time ‘grooming’ the existing wiring — inserting extra slack wire of the main harness through the bottom of the headlamp and routing the harness around the outside of the shell. I disconnected and reconnected wires where necessary to detangle what was there and instill a sence of general order that the S likely hadn’t seen since it left the factory.

It was time to knock off for the evening, so I closed up the headlamp shell and briefly road tested the bike.

It was immediately obvious that the change in the needle jet positions was significant. The bike had reverted to the wheezy, indeterminate operation at small throttle openings that it had exhibited back when I first purchased it. I rolled the bike back into the shop and resolved to fix it during the daylight tomorrow.


After work the next day, I grabbed my trusty offset straight blade ratchet screwdriver, and pulled the tops off the DelOrtos, removed the main jet needle and dropped it to the bottommost position. Making the adjustment on both sides took all of 10 minutes.

I took the bike for a short ride as the sun went down. If you ever find yourself thinking that a single millimeter can’t make a significant difference, you’ve never had a DelOrto carburetor. Throttle response was tremendously improved, and I began to think this really was the end.

I kept right on thinking that until, about 3 miles from home, a friendly motorist pulled up beside me at a light and told me my taillight was out. Now that he mentioned it, my instrument lighting — which had always been at least a tad indeterminate — could now been seen in the darkness to be MIA as well.

I skedaddled back to the garage, nervously toeing my brake pedal now and then to keep some light showing to the rear.


It seemed we had a world-class puzzle.

I hate those.

Upon reopening the headlamp shell, I slowed my breathing and started working my way through the various wiring diagrams and photos, and began to trace conductors one at a time.

Things got weird pretty quickly.

Starting with the ignition switch wiring, it was clear that the bike had been running with two of the switch conductors reversed. It was also clear that Good Old Ham Fist, the previous owner of legend, had, during his installation and removal of his Windjammer fairing, reconnected some things in decidedly non-stock configurations.

For example, where switched hot came from the ignition switch, Ham Fist had actually managed to wire AROUND the fuses on the board. He had taken the outbound connections from the switch, which should connect to a fused bus on the right side of the circuit card, and connected them directly to the distribution connections on the other side of the fuse.

After correcting this little surprise, I started to look to see how the tailight and instrument wires were supposed to be energized. The basic chassis lighting circuit in these bikes is made up of grey wires with black stripes, and those were all connected exactly as they are supposed to be.

These gray and black conductors are energized by three possible methods.

The ignition switch has a ‘Park’ position which can energize the lighting directly. The diagrams all agreed on this point, and when I turned the key to the first ‘Park’ position, the taillight lit, exactly as it should. The second method is another grey wire, also for the park position, that comes from the European-spec switch that allows one to turn off the headlamp, and that worked exactly as it should.

But turn the headlamp on, and the taillight would go out.

I stared at the wiring diagrams for more than a long time. I was missing something, but what? Every wire I could see was in the correct place.

That was when the flash of inspiration hit.

This flash of inspiration, I should add, for those of you that may come here just for your daily dose of irony, was delivered without smoke, ozone, and smell of burning insulation that characterized my previous flash of inspiration. Or flash of the gods punishing hubris. Or flash of whatever the heck it that was that nearly vaporized me and my favorite motorcycle in the middle of Northern Virginia rush hour.

This flash was a fairly simple, but significant thing.

I wasn’t looking for something that was there, but wrong.

I was looking for something that wasn’t there.

The wiring diagram showed a third conductor to energize the taillight coming off of the headlight relay. I looked at the headlight relay, and there was an unused terminal. The diagram listed it as number 87b — with a little convolution and light in the right place I could see the number — 87b.

After two frantic moments at the workbench, I fabricated a connector with a straight blade at one end and a flag connector at the other.

I clicked the connectors into place, and then turned the headlamp on.

Houston, we have a taillight.

Now observant folks will wonder — I know I did — how in Sam Hell the bike managed to work properly before all if this electrical havoc occurred.

And I’m forced to conclude that knowing this is one of those things I’m just never going to possess — its one of the mysteries of the universe.

I replaced the headlamp ring and screwed it firmly into place.

I started the bike and tried all of the electrical system — headlight, parking light, instrument lighting, turn signals, horn, tail and brake lights. This time, we were clean and getting 100% on the QA.

It was time to take the bike back to the road.



In old motorcycles, electricity, and the quality and quantity thereof really drives the performance of the entire system. Ignition coils, capacitive discharge ignitions, resistor spark plug caps and spark plugs all respond subtly but positively to any increases in available juice. It’s what moved the change from 6V to 12V electrics, and it’s what drove the increases in alternator output and better storage batteries.

The best and most recent example I can provide was after the recent replacement of the main ignition switch in my /5 and the upgrade of the battery to a high tech — for a /5, anyway — AGM Deka battery, the whole motorcycle was transformed. The motor ran noticeably smoother, throttle response was better, and the behavior of the motor at top end and its willingness to rev — not that I need to do that with the very bottom end biased delivery of the 900cc motor — were all noticeably improved.

Upon taking to the road, the R90S was similarly transformed. The motor was smoother, throttle response was better. One of the first motorcycle stories I ever wrote was called ‘Stronger Through Adversity’, which was a tale about how breaking things inevitably drove better performance, and that was clearly in evidence here.

The change to the new brake line was also a bonus — there’s much more power available and I’m able to one-finger brake on corner entrances for the first time.

I can only speculate about what may have been sub-optimal in the configuration of the motorcycle electrics before the catastrophe — the ignition switch may have already been compromised, either through worn or burned contacts. Some of the misrouted wiring may have been responsible for choking off the amount of available current to ignition components. The strategic changes I made — by increasing the wire gauges of critical hot feeds, both from the ignition switch to the main board and from the starter solenoid to the diode board, may have allowed more current to the entire ignition system.

What ever it was, though, the change was staggering. With my /5, there really is no top end. The small valves of the 750 cc heads and small carbs can’t really move enough mixture to snap that engine to redline.

This engine, though, is a different beast. The heads are set up for top end operation. The carbs are large and there are long aluminum intake venturies designed to move mixture at maximum load and flow.

After tiptoeing through several brief heat cycles and riding with my fingers crossed for a few days (really hard to open the throttle that way) I got out on one of my favorite stretches of straight road — Md 17 between Brunswick and Burkettsville, and coming out of the traffic circle, went up through the gears WFO. The top end behavior of the bike was transformed — the last 1500 rpms before redline had a brand new snap — there was clearly better fire in those big holes.

There’s a dogleg about 3/4s of a mile from the circle, so we didn’t grab top gear until the exit from that corner. Before the meltdown, it always felt to me that the theoretical top speed of the bike — roughly 125 to 130 mph — was a long way from the ton where I usually begin to lose interest.

It doesn’t feel that way anymore.

Throttle response used to be strong — but in top gear acceleration used to roll off around 90. Today, the calibrated butt accelerometer was pegged — no roll off even in top gear, as the revs came up, so did the power. It was a laughing inside the helmet moment of the first order.

So do I recommend or endorse bursting into flame as a motorcycle tuning method?


But it’s sure hard to argue with the results.


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