Putting a 1968 BMW R50/2 Back On The Road

Published Friday, June 14, 2024 by Bryan

This post is long, so here is a table of contents to help you return to wherever you leave off later.

2021🔗

Three years ago, in that sweet period between when the initial COVID-19 vaccine was super effective and when the Delta variant emerged, we leaped at the chance to finally visit friends in New England we hadn't seen since at least my college reunion two years before that, maybe longer. As we bounced up the hill to their rural farmhouse, we found Becky chasing chickens around a small red shed that Peter was perched atop, nailing down fresh rows of shingles. I walked over to hand up tools and the next row. I quickly got wrapped up in helping complete the roofing as Becky and Amanda wandered off to catch up.

We finished the new roof over the next couple days. One evening, Peter led me to the basement. “I have something down here you might be interested in,” he said.

In an unlit corner across from the stairs, under a coiled hose, several boxes of miscellaneous bits of machinery, and some plastic dust cloth (not to mention the layer of dust the cloth was meant for), was a black BMW motorcycle. I'd love to share a picture of that first view, but believe it or not, I didn't take one.

I didn't really know exactly what I was looking at. I learned to ride motorcycles right as it became an hipster trend to "cafe" a retro motorcycle. The roundel on the tank, not to mention the opposed cylinders marked this bike as obviously BMW, but the other shapes were not those of the 70s and 80s bikes I had seen in blog posts. The valve covers were much rounder. The tank was more teardrop than toaster.

I begged off. I was interested, but this was the first time we had really traveled purely for leisure since the pandemic began, and I wasn't sure how committed I could be to more motorcycling yet. I also needed to do some research to find out exactly what this bike was. Peter told me the model, but I had no context to place it.

2022🔗

When the next summer rolled around, though, I found myself returning to much more motorcycle travel. I had also done my research, and learned that what I was looking at was a "/2" (slash two) series. These started production in the 1950s and ended in the early 1970s when the "/5" introduced the iconic BMW designs most motorcyclists are familiar with today. The particular model in Peter's basement was a 1968 R50.

Three images of three different motorcycles, taken from the side, focused on the front tire.
Three types of forward suspension. Left to right: Telescopic, Telelever, Earles.

What makes this motorcycle so interesting to me is how different it is from everything else I have owned. Even its visual, "spiritual" descendent, my R1150, is completely different the closer you look. Take, for instance, the front suspension - something the R1150 did differently than every other motorcycle on the market during its time. The R50 also has a wildly different suspension, called "leading link" or "Earles-style forks". This was an early design to combat the effects of "brake dive". Its strength also made it well-suited for …

A close-up picture of the side of a motorcycle. Arrows point to three bolt holes and a knob connected to the frame, and currently not connected to anything else.
This frame is prepped for connection to a sidecar!

Sidecar mounts! This was the last BMW series to support use of a sidecar from the factory. There were a few extra parts (alternate rear tire and alternate gearing, mainly) that needed to be changed out as well, but the potential was there and installation is documented in the owner's manual. Of course, the actual sidecars are even rarer than these bikes, but I have been meaning to learn how to weld.

A black-and-white photo graph showing a close-up of the left side of a motorcycle. A person stands next to it with one foot on the center stand, and one hand on the frame. The person is wearing dress shoes and tall socks, with loose-fitting trousers gathered at the knee.
Model of appropriate rider apparel, late 1960s Germany. Also note placement of the kicklever and use of the center stand. (Page 85, R50 Instruction Manual, BMW)

This would also be my first time using a kick-start. This machine is kick-start only, in fact - there is no electric starter. Extra novelty point one is the fact that the kick lever is on the left side, because clearly any civilized rider would start their bike while it is on its center stand, and not after they had already mounted the vehicle. Extra novelty point two is that, since the only remaining electrical draw is lights, the rest of the bike runs on 6 volts, not 12V.

A two-column, three-row diagram, explaining how all turn signal controls for a V-Strom (top) are on the left grip, while for an R1150 (middle) they're split across both grips, and on an R50 (bottom) they're on all on the right grip.
Comparison of directional signal controls across three motorcycles.

In my post about the R1150, I called out how different its turn signal controls were. Guess what - these controls are different still! This time, all signaling has moved to the right grip. I've had less trouble adapting to this one, but that may be partially because I've mostly been using hand signals.

And speaking of the right grip, the throttle is different too. A lot of people get excited about the gear-and-chain mechanism it uses to reduce cable wear. But what's at the other end of the cable is also interesting. This is not my first carbureted motorcycle, but it is my first slide carb. Basically every carburetor you'll find after 1980 or so is a "CV" (constant velocity) carb. When you turn the throttle on a CV carb, the cable opens a butterfly valve. The vaccum of the engine's intake stroke causes air to push the slide after the butterfly up. That helps keep the engine's demand matched to the carburetor's supply. Turning the throttle on this BMW's slide carb directly moves the slide - there is no butterfly. If you've ever read advice about not opening the throttle too quickly, because it might stall the engine, this is why. Open the throttle wide on an engine that's barely idling, and the slow-moving piston won't produce enough vaccum to move the air over the jets at the right speed to pick up enough fuel, and you end up with too little fuel to combust on the next spark.

But even this bike's futuristic features feel foreign. Spark advance is something you'll see me talk quite a bit about later in this post, and is something most people have never thought about in their vehicles. It takes gas a little bit of time to burn. Because of that, when the engine is spinning faster, in order to get the most power from an ignition, the spark to light that ignition needs to happen sooner. Motorcycles (and other vehicles) built not too long before the /2 included an additional lever that the operator used to manually advance the spark timing. This BMW includes a neat contraption attached to the camshaft to do this automatically. As the camshaft spins faster, centripetal force causes small arms on the contraption to fling outward. Those arms are connected to the cam that opens and closes the points (points! another new thing for me!). When the arms open, they rotate the cam so the lobe to open the points sits at a different spot in the shaft's rotation. Very soon after this 1968 model, vehicles would move to electrical timing via various sensors and computers. But this was the year before humans first landed on the moon!

There are a dozen other oddities I'm sure I'd point out if we were standing around gawking at the bike together. I'll leave them for that time, but suffice it to say that this motorcycle became more intriguiging even purely as a curiosity of its time the more I learned about it.

Mid-summer, we began to plan to trip back to New England again. When telling friends about the trip, I occasionally mentioned that I planned to buy, “this old BMW motorcycle a friend has on the east coast.” Alas, just as we were about to make the journey, sudden events caused us to scrap the plan.

Strangely enough, the next month, another friend on the west coast started telling me about another old BMW motorcycle he thought I would be interested in. I ended up buying that one, to the complete confusion of every friend who had heard stories about the other.

2023🔗

And of course when the next summer (2023 now) came around, we had to ride the BMW I had just bought to visit New England friends. It was thus also impossible to bring the R50 home that summer.

2024🔗

So when we started planning this year's visit, I knew what plan I wanted to set.

One of the big questions of acquiring this R50 has been how to get it home. Moving the R1150 from California to Wisconsin was a stressful confusion of supply chain. The pick up happened a month later than it was scheduled. The delivery happened even later, in the dead of winter, on hours notice, while I was in California. (I had informed the company that I would be unavailable to take delivery those few days. They didn't care.) The bike did arrive in the expected condition, but I was a nervous wreck about it by the time that happened. It was a major relief when I actually enjoyed riding it later that spring.

I didn't want to use that same motorcycle shipping company for the R50. I'm not a huge fan of U-haul either, after several frustrating experiences with them as well. Our car isn't rated to pull a trailer, though many claim it can deal with light ones just fine. Should I borrow a pickup or van?

No! I knew what I wanted to do. I wanted to ride the R50 home.

One problem: the R50 hadn't run in over 20 years. It had been parked inside the whole time, so the seat, tires, and other non-metal bits hadn't rotted off. Someone had also oil-misted the cylinders, so the kick-start lever still turned the crankshaft smoothly. But Peter's son had also begun, and later abandoned, some maintenance between then and now. Carburetors were bolted to cylinders, but not connected to fuel lines. The petcock attached to the fuel tank was obviously a replacement. Spark plugs sat free of spark plug wires. The battery was missing.

Last winter I found a new YouTube channel to enjoy: The Bearded Mechanic. I found myself energized by Craig's enthusiasm in video after video as he looked into the camera and asked the audience, “Can I make this 19xx classic run, and then drive it a few hours home?” Sometimes he could, sometimes he couldn't, but he always had fun celebrating the progress he made along the way. (Seriously, if you need a moment of joy, watch Craig and his camera man, Dan, react to hearing an engine fire up for the first time.)

But could I make this 1968 BMW R50 roadworthy for a 1300 mile trip home? I, unlike Craig, am not a trained mechanic. I do lots of my own basic motorcycle maintenance, but I have never torn apart an engine. I once fixed a small Honda by removing, disassembling, cleaning, and reassembling its carburetor. But that's a Honda - we all know it would have run without any work if I just pushed it hard enough. It was also half of this bike's age.

So I watched every video I could find about these motorcycles. Seroj Terian rebuilding the engine. The BMW Guy doing basic service. Chris Harris doing more technical service. I read Jeff Dean's page devoted to the /2. I downloaded manuals from Vintage BMW and read them. I ordered a Clymer manual and read it. I wrote back and forth with Peter about what parts he had, and what state he remembered various bits being in, based on what I had learned.

And then I started ordering parts. I over-ordered, for two reasons. The first is that everything I ordered were things that if I didn't use them to get the bike back on the road, I would use them in a future service to keep it on the road, so no value would be wasted. The second reason is that our visit would be over Memorial Day weekend, so if I didn't have it when I arrived, I wouldn't be getting it for several days.

As the trip approached, I also prepared a toolbox. Peter is also a handy person, so he would have every tool I needed … while I was there. For the four-ish days I was planning to ride back, I would be on my own. Amazingly, the original toolkit was still with the bike, but I also wanted tire repair utilities in case of a flat, various sockets to make bolt-spinning easier, a multimeter to chase wires, a good light in case any of that had to be done in a dark parking lot, etc.

Wednesday🔗

So it was that we pulled up Peter's driveway on a Wednesday afternoon with a hatchback full of tools and parts. After some catching up, we made our way to the basement and started preparing the workspace.

A black vintage motorcycle, dusty and dirty, still looking great.
The earliest image I have of the 1968 BMW R50, taken just after we moved it into the workspace.

I should have taken a much more measured approach. Cleaning first would have been a good call. Maybe even waiting for morning to break out tools. But I was so anxious to dig in and find out what the state of things was. We started pulling bits off almost immediately.

Channeling the Bearded Mechanic, I wanted to look at the fuel tank first. I opened it and peered inside. Spotless! The red liner common to BMW tanks seemed completely intact with no obvious rust breaking through. The fuel, though, did not smell right - sweeter, maybe pine-y? Peter found an empty gas can and we drained it.

The air filter was the second place I knew needed to be checked. If anywhere was going to contain a mouse nest, it was there. It took the penetrating oil a few minutes to loosen the rust holding the filter enclosure together, but when Peter separated the lid from the body, we found … a dirty, but otherwise intact filter. No sign of mice at all - hooray!

I turned my focus to the carburetors. I had already planned to take them apart for cleaning, but while going through nearby boxes of parts, we found a rebuild kit. Obviously someone had already planned some carb work. When I got the right carb stripped, it was obvious why - every jet had some bit of gunk or corrosion clogging it. I laid out the old parts next to the parts in the kit and found that the only part we didn't have a replacement for was the float needle. That seemed reasonable - we didn't have a replacement for that needle's seat either. Luckily, it also looked in reasonably good shape.

We broke for drinks and dinner before I could reassemble the first carb. That was a good idea - coming at a delicate assembly fresh would reduce the likelihood of errors.

Thursday🔗

Once the carbs were each reassembled and reinstalled the next day, I got curious about spark. The spark plugs were laying loose in the recesses leading to their ports in the upper sides of the cylinder heads. One had a quarter inch ring around it that had detached from the boot at the end of its wire. I decided to ignore the old spark plugs, and give myself the best chance for success by just using the new spark plugs I had brought with me. I plugged them into the boots, and for the first time pushed down the ignition key and gave the starting lever a kick. We had spark! That was a fantastic sign. I replaced the boots anyway, to keep a better weather seal, but I wouldn't need to worry about the points, condenser, coil, etc. right away.

I ended the day prepping the other half of the electrical system. This bike technically doesn't need a battery to run - it's kick-start only, so there is no starter motor to draw on a battery! But for lights while the engine was not running, a six volt battery is required. Yes, 6V not 12V as is standard in most vehicles today. I had picked one up on our way in, but because I had ordered it online, they hadn't included the acid for it (they can't ship that). Luckily, Peter had acid leftover from a battery they hadn't used. I sat for several minutes with a small syringe moving acid a little at a time from the pre-packaged six-port applicator to my battery's non-matching three filling ports. When the battery had cooled down again a couple hours later I attached a six volt trickle charger, and in the morning the charger reported full power.

A close-up of some grey denim. Many small holes speckle its surface.
My pants suggest I was not quite as careful with the battery acid as I thought I was.

Friday🔗

Instead of diving right back in in the morning, I ran out to an auto parts store for fuel filters and fresh oil. I would need the former to run the machine, and the latter shortly after its first run. And that first run felt like it was getting close.

I knew I wanted to check one more thing before our first attempt at starting this motor: valve clearances. I'm glad I did. According to the feeler gauges that came with the bike's toolkit, every valve rocker was too tight. I carefully adjusted them and began putting the valve covers back on.

That's when disaster struck. The center of each valve cover is secured by a cap nut on the end of a threaded rod, the other end of which is screwed into the cylinder head. As I tightened the cap nut on the left cylinder, I felt it tighten down … and then suddenly get loose again. At first I thought my socket had just bound on the wall of the recess the cap nut lives in. But when I withdrew the socket, out came the cap nut and the threaded rod. The rod had stripped out of the cylinder head.

I swore and went upstairs for lunch. We talked over a half dozen fixes. Was that securing point actually necessary? It should be a lower-pressure zone, so could epoxy hold it? Would epoxy melt at cylinder head temperature? Could the hole be made deeper or wider and retapped for a new bolt? What color locktite should we use to thread it back in?

Fed and recaffeinated, I returned to the workspace to look at the problem with fresh eyes. Interesting note number one was that the hole into which the rod threaded was open at the far end. There is a space for air to circulate immediately above the cylinder. That meant that we wouldn't have to be worried about damaging the actual head if we needed to drill. It might also mean that the rod's connection point might have a slightly lower temperature than the rest of the head.

Interesting note two was that the threads weren't completely gone. After cleaning aluminum out of the rod's threads, it still found something to grab in the head, and it grabbed better deeper in the hole. I found a tap that matched the rod and carefully threaded it into the hole in the head. Clearing out detritus, I was able to add a couple more revolutions to the bottom of the hole.

Interesting note three was that the threaded rod in the right hand cylinder didn't look at all like the threaded rod I had pulled out of the left. Someone had stripped and/or replaced one of these before!

I decided that the rod was holding well enough to just be screwed back in, but also decided that I wanted to apply red "permanent" locktite to it. Unfortunately, we only had several tubes of blue "removable" locktite. I'd have to wait for the next day to acquire some red.

I used the rest of the day to finally install fuel line, to install the battery and check lights (they worked!), and to have a look at the points even though I already knew we had spark (they looked near perfect, and were spaced great too).

Saturday🔗

We had met friends of Becky & Peter's for dinner the previous evening. Among other things, we had discussed my work on the BMW. Charlie, a long time friend of Peter's, had been excited to hear about it, remembering Peter riding the motorcycle to work in their early careers. Charlie being another handy fix-it person, also happened to have red locktite on hand. We visited his place in the morning, and picked up a tube (as well as a ground-penetrating radar that Charlie and Peter were fixing and using for various land-improvement projects - another story for another time, but more flavor of what I really mean when I call these two "handy").

With the threaded rod secured in place, and valve covers bolted on, the moment of truth arrived the next day. We laid a piece of plywood on the grass outside of Peter's basement shop. We rolled the bike out and popped it up onto the plywood. We added fuel to the tank. I flipped the petcock to reserve, then gave the starter lever a couple of priming kicks. Finally I reached over and popped the engine key down into position, and kicked it over several times assertively. Half a dozen kicks in, and we got a short putt, putt, putt. Excitement all around!

But that was where it stopped for the moment. It would almost catch and run, but just couldn't maintain idle. A bit of inspection revealed that the right fuel filter wasn't getting fuel consistently. We're all scientists and engineers, so we went through stage by stage - we got fuel from the petcock, from the upper bit of hose, through the filter, and out the bottom end, but only when we had each of those points disconnected from the rest. All together, fuel wouldn't flow. We disassembled and cleaned the petcock. Indeed, there were a few bits of crud in its screen, as well as a bit of silt in the tank. I reassembled the double-banjo-bolt setup so that the nozzel for the right cylinder was below the left, instead of above as it had been earlier. It seemed like maybe fuel was flowing better.

We rolled it back outside, and I started kicking again. We didn't have the cameras rolling, but it wasn't too many kicks before the engine came to life! For the first time in nearly 25 years, it was running!

I quickly grabbed a helmet and gloves. It had to be ridden. I hopped on, and up and down the driveway I went. Once, twice, three times, I lost count. Eventually I pulled up next to Peter. “Are you coming for a ride?” I asked.

“Let me see if I still have a helmet,” he replied and disappeared into the house. When he emerged a minute later - I may have made another lap in the meantime - he had found a classic black motorcycle helmet. He hopped on the back, and we took off around the house.

Two men on a black classic motorcycle riding down a gravel driveway.
Running and riding!

With smiles all around, and excitement at a real milestone of progress, I thought the next best activity was to change all of the oils while they were warm and fluid. There are four separate oil compartments on this motorcycle: the engine, the transmission, the shaft drive, and the final drive. They use two or three different oils, depending on riding conditions. I decided that the forecast of 75-80°F combined with my plans for highway mileage constituted "extended sporty riding in warm conditions" and chose SAE 40 oil for the engine, over the SAE 30 suggested for more relaxed, colder riding. That meant I could use the same oil for the engine, shaft, and final drives, and needed only one other oil for the transmission (10W30).

Sunday🔗

The next day, I wanted nothing more than a real test ride, but knew that I needed to complete more maintenance first: tires and brakes. The wheels had held enough air to allow us to move the bike around the shop and toodle around the yard, but I wasn't going to trust 35mph or more on a public road to 25 year old rubber.

Changing tubeless street-bike tires is generally not fun if all you have is a pair of tire irons. It is hard work getting a tire on and off a rim. Add in getting a tube in and out between them, and you're in for a sweaty time. However, this bike uses tube-type tires. Tube-type tires are typically reserved for off-road use these days, but there are a small few treads designed to evoke the original look of a classic bike. Unfortunately, the last person to change the tires had installed tubeless style. So we had a bit of a struggle getting the old tires off. Getting the new tube-type tires that I had brought on was not easy, but it was definitely easier that the tubeless tires I had changed in the past.

The biggest mistake I made was being so happy and tired (ha!) about getting the new rubber on that I forgot to pull out the balancing jig I had brought along. I lined up the dots with the tube stem. It's probably fine. I'll check it another time.

I did remember to take a look at the brakes while the wheels were off. This bike uses drum brakes - two shoes up front, and one in the rear, housed inside the wheel hub. Peter had two shoe liners on hand, and I brought fresh rivets to install them. But with the wheel off, it seemed we didn't need to. There was still plenty of material left, and no oil or grease fouling that we could see. I readjusted the free play in the cables after I reinstalled the wheels, to make sure I had plenty of travel to give them a good strong squeeze when needed.

After also lubricating all of the control cables, I quickly claimed the last of the afternoon for a more serious test ride. I backed the bike out of the workshop, gave it a kick, and it started, first try! I was amazed. Did it really just need fresh oil to loosen up?

I set off down the driveway, and turned onto the road. It felt good. The engine was running pretty smooth. The suspension and handling weren't perfect, but they were perfectly acceptable. I motored past the post office, and over the next hill.

It felt like everything was going well until a loud POP sounded from the exhaust. The engine stumbled. I pulled over in the next driveway I passed. As the bike calmed to idle, it seemed to restabilize. But as I got back on the road in the direction home, I found that I had very weak acceleration power. With the throttle wide open, the engine would barely pull me up a hill in second gear. Finally, as I throttled down to make the turn into the driveway, it quit.

Hopping off, I knew exactly what to check. The fuel filter leading to the right hand carburetor was dry again. I pushed the bike a few yards up the driveway and stopped to think. I wouldn't be able to push the bike all the way up the hill. I could call Peter and ask him to bring a tractor down to fetch me. But what I did instead was pull the hose off the top of the fuel filter. That got fuel flowing again, which I was able to trickle into the fuel filter. Once primed, the filter passed enough gas through to restart the engine, and I was able to ride to the top after all.

A hand holds a fuel filter on the left, inside of which is a pleated paper element. A smaller, flatter fuel filter is attached to hoses on the right.
The right-hand carburetor was starved by the fancy fuel filter on the left, but ran happily with the fuel filter on the right.

When I reached the top, Peter appeared with an alternate fuel filter. This one was the style I was looking for in the first place - not a cylindrical paper filter, but instead a pancake with a screen in the middle. Autozone just hadn't had any the morning I went shopping. The combination of a freer passage, with a slight change in the angle of the hose leading from the petcock to the filter, has led to never having fuel starvation problems with the right carburetor since.

Monday🔗

The next day it rained. Just a steady pour all day long. I think we all welcomed it. We embraced the forced down time by reading books and taking naps.

We also accidentally watched one of the funniest movies I've seen in a while. Peter was trying to figure out what had gone wrong with his DVD player last time he had tried to use it. He put in 1966's "The Wrong Box". There are a number of well-known comedic actors in this movie (Peter Cook and Peter Sellers, to note two), but Michael Caine (best known to my generation as various forms of stern elderly gentleman) in such a role was completely new to me, and absolutely wonderful.

Tuesday🔗

But the day after that was our last full day in New Hampshire. I needed to get out for another serious test ride. If the bike couldn't stay running for several hours, I couldn't ride it home. I charted a test plan:

  1. Ride to the gas station, another couple miles from where I turned around last time. Fill the tank.
  2. If the bike started again, ride a short loop staying within a few miles of the farm.
  3. If the short loop went smoothly, ride a longer loop.

Check. Check. Check. I spent nearly four hours out riding that day. Something like 120 miles of fun backroads. It was glorious. I stopped and started a few times, as nature called, and just zipped around without any issue at all. Maybe this was going to work.

A classic black motorcycle parked in front of a dense mountain forest.
Cleaned up a bit, and out on the road.

We put away the tools that night, and I got the spare parts boxed up for the trip home.

Wednesday #2🔗

The next morning, we packed it all back into the car, and I hopped on the bike. I followed Amanda as she led me toward Boston.

My original plan had been for Amanda to follow me. She could help keep aggressive and distracted drivers off my tail. But there was one thing that I hadn't been able to fix: the speedometer. I had learned it didn't work on my first test ride around the yard. After some poking, we learned two things: the speedometer cable had snapped internally, and the speedometer-odometer unit was frozen. We imagine the latter caused the former, but it's all a bit odd because that speedometer was not the original. The original was sitting in a nearby box, in apparently perfectly working order. I swapped the working unit back into the headlight nacelle, but we had no replacement cable. That was a part I hadn't ordered beforehand, and couldn't be acquired over the holiday weekend.

The silver gizmo with the neon string attached to the handlebars in the upper right is an airspeed indicator.

So instead of a cable-driven speedometer, what I had taken my test rides with was an airspeed indicator. Peter had one on hand from a windtunnel project he had done a few years before. We strapped it to the handlebars, and I used my common sense to determine how much I trusted the reading on my longer test drive. On this drive to Boston, though, I could know exactly what speed Amanda was driving (she obeys the posted limit strictly) and compare that to my readings. It turns out that setup wasn't too far off up to about 40mph.

An hour or so into the journey south, we stopped for a bio break in Rochester, NH. When we had finished our coffee, I suited back up and worked at getting the bike restarted. It was being stubborn about it this time. After a number of kicks, I suddenly noticed Amanda leaning out the car window as she said, “Is it okay that there is smoke coming out of the headlight?”

No, it was very much not okay. The smoke increased. “Uh, oh. We have a fire. I need the toolkit. Now,” I replied. As I pulled the ignition key to cut power, Amanda jumped out of the car and extracted the toolkit from the trunk. I unscrewed the headlamp's retaining screw and pulled it off the nacelle. Smoke puffed out, and I found several wires melted to each other.

There was no active fire, though. I decided the smartest thing to do would be to disconnect the battery before probing around. While I got into that process, Amanda headed off to a Staples across the street. Believe it or not, one thing I hadn't put in my toolkit was electrical tape. I'm still not sure how. Luckily, Amanda found a rainbow selection of Scotch's finest at that Staples.

A hand holds a brass-colored cylinder. A wire terminal protrudes from one edge. A charred whole in the other edge indicates where a similar wire terminal used to be. The headlight hangs from the motorcycle, out of focus in the background.
The turn signal flasher unit, after its magic smoke was released.

Once I dug into the tangled mess, I learned some of what had happened. Somehow the turn signal flasher unit had found a way to short its contacts across a grounding wire. Whether this was the result of my speedometer work, or of work on the mirrors that I haven't even told you about, or just an inevitability of shaking an old machine, I may never know. The smoke had been mostly the internals of the flasher unit, so I disconnected it and stored it away in the toolbox. I would just make hand signals for turns the rest of the way.

The conducting bits of the wires seemed to be in fine shape, but the rest of the smoke had been their insulation. We rewrapped the conductors in plenty of color-matched electrical tape, and then carefuly tucked them into safer places. I reattached the battery, and tested power. Hooray, the headlight and tail light still worked! With the seat reattached, the bike mostly started without complaint and we set off again.

As we crossed into Massachussetts, we joined slower and slower traffic. I had been comfortable covering miles through New Hampshire, but now I was starting to sweat. As we neared Woburn, MA, the bike stumbled leaving stop signs a few times. I attributed it to my own fatigue at the controls, but also flipped the petcock to reserve, in case fuel was burning faster than I expected.

We made it to our hotel in Woburn just fine. But an hour later, we were supposed to drive over to Waltham to meet friends, and I just couldn't get the bike started. Several minutes of kicking passed. Occasional putts never made the transitional to running. "Just one more kick" later, it finally did start. I hopped on and headed for the parking lot exit. The engine stalled again when I pulled in the clutch to stop at the light. Running late for dinner, I hustled the bike to an empty parking spot, locked it up, and hopped in the car with Amanda instead.

Thursday #2🔗

I had hoped to do some troubleshooting the next morning, but it was pouring rain again. We left the bike covered where I had parked it, and set off to run errands and meet other friends. By the time we returned, it was already getting dark.

Friday #2🔗

The next day I woke up early. In the parking lot, I once again broke out the tools. I pulled the spark plugs - were they maybe a little looser than I remembered tightening them? They looked "fine" - a little brown, maybe, but I've seen worse. I laid them on the cylinder heads and gave the bike a couple kicks. They still sparked. I screwed them in, snugging them up just a hair more.

I checked the fuel supply. It seemed like gas was getting to the carburetors just fine. Since the spark plugs had seemed loose, I checked the carburetor mounts. They also snugged just a bit more.

Running out of easy things to check, I gave the bike a couple kicks. It started! It sounded a little rough, but it started. I quickly rode it over to the nearest gas station and topped off the tank. It restarted easily, and I rode it back.

After tooling around the parking lot for a bit, I set it on the center stand to idle. It was still running rough. I broke out a wrench and a screwdriver and decided that tweaking the fuel-air mixture might be a good idea. I had been thinking about the hot day, and how it is often noted that a lean mixture will run hot. Would a richer mixture help?

I twiddled the right-side mixture screw a bit. With the fuel supply trouble we had had on that side, I wouldn't have been surprised if its mixture was wrong. But by ear, it still seemed about right. On to the left side. A half turn farther in, and suddenly the engine was running smoothly again! I revved it up and let it settle a few times, and it seemed to once again be happy. This was the opposite of the way I expected to turn the screw to richen the mixture, but I couldn't argue with the results.

Saturday #2🔗

The bike had to sit still for another day. Part of the reason for this trip was to attend my college reunion. We had a great time catching up with old friends, and they all wished me luck on my journey home.

Me posing in front of a red photo backdrop that says 'MIT ALUM' in several places. I'm wearing a baseball cap and a grey T-shit promoting 'Hodag Curling'.
Maybe time for a new profile picture.

Sunday #2🔗

When Sunday morning rolled around, I once again had some maintenance to do. The friends we had seen in Waltham had helpfully been my local mailing address, to receive my order of a new speedometer cable. I had to remove the seat and unmount the gas tank to do it, but I unthreaded the old broken cable and threaded in the new one. Shifting the bike into fourth gear and kicking the starter made the needle move!

I unstrapped the airspeed meter, and replaced it with a generic clamp-on mirror. Maybe I'd be able to watch my own tail while also being sure of how fast I was traveling!

Amanda got the rest of the luggage packed and into the car. We added the tools, and I suited up. Fuel on, primer kick, key on, slight crack of the throttle, and the R50 started on a single kick! We made our way to the parking lot exit, and the speedometer told me we did that at 15mph! Everything was coming together perfectly.

We couldn't dawdle on 40mph backroads the whole way back, due to future schedule commitments. But I also wasn't ready to attempt a long 70mph stretch on I-90/Mass Pike. So we compromised on MA-2. The R50 hummed along at 55mph happily. I took it up to 60mph for a bit just to pass Amanda. We pulled off around Devens (34 miles later, thank you working odometer!) to refuel the car.

We decided that things were working well enough that we'd give Mass Pike a try. Back onto MA-2 we went, before merging onto I-190 near Leominster. Sixty miles per hour had been okay. Sixty-five took some work to maintain. It was taking me a little extra work because the right turn signal at the end of the handlebar had rattled loose. I was happy that the throttle didn't automatically close itself, so I could mostly leave it twisted open while holding the turn signal assembly.

I had been planning to signal Amanda to pull off around the I-90 interchange so I could address the turn signal issue, when suddenly the engine started running rough. I could no longer maintain 65mph. Even 55mph was slipping away. I started flashing my headlight and took the next exit. The bike threatened to stall if I rolled off the throttle too far, but wouldn't run smoothly when I rolled on the throttle. I somehow kept it going through a couple stoplights and eventually parked in a school lot.

I texted Amanda, because she hadn't been able to make the exit I took. She had seen me take it though, had gotten off at the next exit, and was routing back to me.

When she found me, we once again broke out the toolkit. First I removed the loose turn signal. I was very happy that Peter had shown me how to do this while we were lubricating and adjusting the throttle. It's not an obvious process the first time. I used more electrical tape to insulate the loose wire (which was probably already neutral without the flasher unit installed, but better safe than sorry) and stuffed it back in the open end of the handlebar.

The rough running felt something like running out of fuel - like one or both cylinders were occasionally missing. I had only ridden about 60 miles since last filling, so it would be a major surprise to be low on fuel. I opened the tank to check, and it was more full than I had seen it on other successful rides. But, given the fueling problems I had been chasing, I thought that more fuel couldn't hurt, so we limped to a filling station a half mile down the road.

With a tank full of fuel, I moved the bike to the edge of the lot, and got it restarted and idling. Adjusting the mixture had settled it down last time, so I got out the tools to do that again. It was over 80°F outside today, significantly warmer that the last time I had adjusted it. Maybe a hot adjustment would keep it happy.

After a few tweaks, it did seem like the engine ran smoother. We loaded up and rolled out. But the bike stumbled again as I tried to accelerate on the street. I swung into another parking lot just a couple blocks on.

As one last-ditch effort we left the bike and drove to two different auto parts stores to find the last piece I had really meant to install: another simpler fuel filter. Peter only had one, so we had used it to replace the troublesome filter on the right side. The left side had been, so far I thought, just fine with the paper filter. I wasn't going to change it if it was working, but now maybe it wasn't working.

With the new filter installed (thanks, O'Reilly), I played with the idle screws and mixture one more time until things sounded okay. We rehydrated, recaffeintated, and boosted blood sugar at the Dunkin's next door before setting off one more time.

But sadly, it was the same story. The engine stumbled any time I tried to accelerate. Into another parking lot we went after another couple blocks. Out of ideas of what more I could test and fix in a parking lot, it seemed time to enact the backup plan. Amanda pulled up the list of U-haul locations she had assembled that were willing to rent us a 10-foot truck for a one-way trip. “I was prepared for this two hours ago, but wanted to let you keep trying until you were as well,” she told me. That's not a dig at all - in fact, I had packed ratchet straps knowing that this was a potential plan.

We left the bike once again to go rent the truck. I thought about finding a Home Depot on the way back, to buy some 2x4s to construct a frame. But Amanda came up with a plan for wedging the tire into one corner that worked perfectly. The only hard thing we had to do was get the bike up into the back of the truck. Ten foot trucks have lower decks, but no ramps.

Along one edge of the parking lot, the ground sloped up a couple feet. I backed the truck over to it. The bumper would be an easy lift. The deck would be another eight inches or so. I got the bike in position, and with me on one side and Amanda on the other, we popped the front tire onto the bumper. “One, two, three,” and we popped it up onto the deck.

Bang! The oil pan hit the deck. Or maybe the cylinder head hit the edge of the door. I'm still not sure, but the sound was like the Bat Signal for an amazing stranger who had been picnicing with his family a few yards away. He came running. We maneuvered the bike forward and back until the cylinder cleared the door, and then I had Amanda get up in the back of the truck to stabilize the steering.

“One, two, three,” and the stranger and I lifted the rear of the bike, rolling it forward into the truck. I thanked the man profusely and pressed cash on him to make sure the sentiment registered sincerely.

Me, in the back of a box truck, attaching a classic black motorcycle to the walls of the truck with yellow ratchet straps.
That's not going anywhere.

After a few rounds of ratchet strap experimentation, we found a configuration we liked and set off on the road once again. Amanda continued to lead in our car, and I followed in the U-Haul. We tried the other way around occasionally, but it was so much easier for her to pick out my white and orange box truck in her mirrors that it was for me to pick out her little grey hatchback in mine. I think I'm also happier playing catch up.

After being quite sad that I had to end the bike trip, I found that I was quite happy to drive the truck. There is just something about driving a big vehicle - a large van, a box truck, anything towing a trailer - that makes me the absolute chillest, most friendly driver. I started surfing the radio stations, settled into the comfy chair, and let the miles roll by.

Tuesday #2🔗

We arrived home two days later. We'd normally be more leisurely in our pace, but why keep a rental in our possession longer than necessary? It would also be nice to have a couple extra days to decompress before our next adventure. We rolled the bike safely down a make-shift ramp (a five-foot 4x8 beam a neighbor had thought to alert me to before it went in their dumpster). Our tie-downs had worked perfectly - the bike was upright and completely undamaged, despite the best efforts of Ohio's road surfaces.

Today🔗

This section has a companion video. Watch it on my YouTube channel: Putting a 1968 BMW R50/2 Back On The Road

It rained for two days after we got home. I finally got out on Friday to look things over. I strongly suspected that if I simply turned the gas and key on, and gave it a kick, that it would start without complaint. But I wanted to have a look at things in the cool comfort of my own garage.

I started with the spark plugs. They were definitely loose again. I was able to remove them with just the socket tool, no leverage bar required. This concerns me. I know that over-tightening spark plugs is a very common cause of engine damage - it's too easy to strip the threads out of the engine. So I've been tightening them the way I tighten every spark plug on my machines - just a bit tighter than hand-tight. Just tight enough that I can't loosen them without a little leverage. Is this not tight enough, or is there a problem with the threads that just won't hold them? I'll have to see if I can get a regular socket that will allow me to put a torque wrench on them next time, to make sure they're really tightened to spec.

But more interesting than being loose was how the ends looked. The left plug looked about usual - slightly brown, though maybe just a touch oil-glossy. It wasn't enough oil to worry me, especially as these engines are known to leak a touch of oil into the left cylinder if the bike is left on the side stand too long. The right plug, though, was completely carbon-fouled! A clear layer of black, sooty deposit. My maintenance books suggest this likely indicates too rich of a mixture, or poor spark (it's not the wrong temperature plug - these are the exact model recommended by BMW). I wouldn't be surprised by a mixture issue, after all of my twiddling. But spark was on my list to check anyway.

I cleaned up both plugs, stuck them back in their boots, and grounded them against the cylinders. With the key on, I gave the engine a couple kicks. Spark in both plugs! I don't have an easy way to tell if it's "good" spark, but it was blue and visible, so I checked the box.

I wanted to check on the rest of the ignition system anyway, so I disconnected the battery and pulled off the front cover. The points still looked great. The coil still looked old, but no worse than the first time I had seen it. I checked the safety gap between the high tension wires and the ground tips. One was perfectly in-spec, the other just a little wide. I bent it into spec and moved on.

The spark advance mechanism is one of the components I'm most suspicious of. It is a super cool little whirlygig, with arms that fling out as the engine revs up. Those arms are attached to the cam that opens the points, and they cause the cam to shift the opening earlier at higher RPM. If that shift isn't happening, my spark is happening too late when I'm trying to accelerate.

I've verified that the arms move, but I don't know if they move freely enough. To learn that, I need to attach a timing light and watch the marks on the flywheel under its strobe to see when the spark actually happens. This will happen soon, I just need to arrange access to the tool.

I attempted to add some grease to that area. It's probably the wrong kind of grease, but it seemed like anything would be better than nothing. I'm also not sure that the little bit of felt that's supposed to hang onto some grease is in great condition. When I order its replacement, I can order the proper grease to apply to it.

I put the front cover back on, reattached the battery, and turned my attention to the carburetors. I had decided that resetting the mixture screw to its recommended start point (a turn and a half out from bottomed) was a good idea, after seeing the soot on the right spark plug and losing track of where I had left them before hauling anyway. I did all that, and then turned on the gas at the petcock.

But before I could even kick, fuel started dripping from the carbs onto the floor! Apparently the float needles weren't seating right. I closed the petcock and thought about what to do. Siphoning gas out of the float bowls would be fiddly. Some people suggest flooding the float bowl on a cold start anyway. I decided to leave the petcock off, and just kick the engine over.

One kick. The bike started right up. Not super smoothly at first - a pretty slow putt that slowly became a lope. It eventually made it to an uneven purr about the time the float bowls emptied.

I removed the lids from the float bowls to have a look. Maybe I imagined it, but it seemed like the needles stuck a bit as I lifted the lids. I hope this wasn't damage from shaking in the back of the U-haul. The points of the needles looked about like I remembered them, so probably not. It's difficult to see their seats up in the supply spigot in the lid. But, I carefully reattached the lids, and when I opened the petcock again, no fuel leaked. Maybe I cleared some speck of junk.

Time to play with the mixture again. I set up some fans to move cooling air over the engine and clear exhaust fumes while I worked. Again, one kick and the engine came to life. It took it a while to warm up enough to respond well to throttle manipulation. But eventually it did, and I could rev it up a little and then let it settle back down to idle without worrying it would stall.

I fiddled with the mixture screws. The right carburetor really seems to like the standard 1-1/2 turns out. A quarter turn farther in, and it starts loping. A quarter turn farther out, and the idle picks up speed. I believe that right in the middle of those is where you want it. The left carburetor needed its idle screw backed out a half turn or so before any adjustment of the mixture screw had a noticeable effect. I think the left exhaust still sounds more rumbly (not "poppy", but "burbly") than the right exhaust. The few times I've adjusted the mixture before, it seemed like I was able to tune that burble out. This time, I think I'm still hearing it.

I played the idle screws a bit more. That did seem to even the sound out. Carb tuning may be something that I need to ignore for now, and return to after checking other issues.

With the bike running again, I suited up and took off for a test ride. As I pulled onto the street, I rolled on throttle. I couldn't have gotten above 3000 RPM before the engine started coughing. Almost acting like it was out of fuel. I rolled off and turned around. Low RPM was fine. I shifted into second, and was able to accelerate, but as I got up to 3k or so, it coughed again.

I decided it would be a good idea to run it a little more, to see if some warmth and movement would loosen things up. I set off toward town, keeping the engine speed low. A nice thing about these boxer engines is that they have enough torque that they will still accelerate, even at RPM you'd consider lugging on any other twin. I put about 17 miles on the clock by the time I returned home. Third gear would happily bob me along at 35-40mph, and fourth gear could carry me alright at 45. If I had had the time to do it, I think this bike would have successfully carried me all the way back to Wisconsin at 40mph.

A person wearing a yellow motorcycles suit and a white helmet sitting on a black classic motorcycle.
If you'd like to hear the R50 start and watch me ride it away, skip to time code 27:12 in the video.

The Future🔗

I'm not going to leave the engine struggling at high revs. I have a list of things I'll be checking in the near future:

  1. Carburetor cleaning. These float needles shouldn't stick. I wonder if the float bowls are often flooded, causing the level to be wrong at the main jet. Or maybe the main jet has some restriction. I was hopeful that the fuel filters I installed (as well as the one in the petcock itself) would keep grime out. But there might have been some already in there that I didn't properly clean out last time. I'll disassemble them to look, and give them another thorough cleaning while I'm at it.
  2. Spark timing. I mentioned this earlier - that spark advance mechanism might be sticking. It's an easy thing to check, once I have the tool to do it.
  3. Spark strength. History with my V-Strom taught me that magneto and coil windings can behave in odd ways - operating completely normally at "low" temperatures, but shorting at high ones. Of all the things, I knew that this was one I would be completely unable to test in a parking lot. Another special tool is required to check the coil, though. I wonder if a friend has one.
  4. Compression. This one's an outside chance, but it's another thing I haven't measured. This is a relatively low-compression engine. I checked that there was "some" compression by holding my thumb over the spark plug hole. I felt positive pressure as I turned the engine over. It wouldn't surprise me at all, though, if the amount of compression in each cylinder is different, or if it changes as the engine heats up. Maybe it even changes as those spark plugs loosen?

I could be completely wrong. As I said at the top, I'm not a trained mechanic. But I've gotten at least a, “Those are good hypotheses,” from someone who is. And carb cleaning isn't too difficult on this machine, so why not try it anyway?

I also haven't decided exactly what to do with this machine other than enjoy riding it. Someone asked me along the way what my plans were. “Are you going to do a full restoration? Or a resto-mod?” I really don't know. It definitely needs some restoration. I haven't even told you about the exhaust leaks that we treated with asbestos and band clamps, for example. I'm going to try riding it for a season, and see what sorts of rides I enjoy on it before considering any changes, though. As a member of my "stable", it has a very different character than either the GSA or the V-Strom. I expect it will be loads of fun just bopping down a backroad to the farmstand or the coffee shop or the ice cream parlor.

But I absolutely intend to ride it. Part of this is that I'm not much for display - if I own something, I expect to use it. But also, I have already learned how much other people enjoy seeing it. Across the few days I rode the R50, I did not make a single stop where I didn't end up talking to at least one person about it. Literally the first gas stop, someone yelled from the next pump over, “Hey, what year is that?” I heard the same question from the park ranger as I headed for the restroom in the middle of my test ride. Every person that walked by as I was fixing the headlight wanted a picture. The contruction workers behind the hotel were eager to move a pickup out of the way for me. The U-Haul employee that saw my motorcycle-related apparel wanted to see pictures. In fact, the only person who didn't really talk to me about it was the guy who helped us lift it into the truck, and I'm pretty sure that was entirely language barrier-related.

I began to recognize something a very good friend told me. We took his Ferrari (one of the actually-a-race-car-but-street-legal models) out driving one day. At the base of a well-known drivers-delight mountain road, he pulled over and put me in the driver's seat. I had never driven a vehicle like that, but he was insistent. He told me as I carved corners that he had come to believe that the point of owning such a special vehicle was sharing the experience with others. He loved driving the car, but got as much, or more, enjoyment out of watching his friends enjoy driving it.

I was experiencing a similar realization. The R50 is absolutely fun to ride, but it's also a ton of fun to watch people get so excited about seeing it ridden. I was bummed not to be able to ride it across the country for my own enjoyment, but also a bit sad to miss all the folks who we would have met at stops along the way. People are genuinely happy to see a machine like this taken care of, still running, out enjoying what it was built for. And so that's what I plan to do with it.

Acknowledgements🔗

Getting this motorcycle back on the road, and all the way home was a huge project. Many people helped along the way, and because I'm sure I haven't recorded their contributions well enough in the story, I'm going to thank them here.

First up is Peter, the original owner of this BMW. Thanks are due not only for offering me the motorcycle, but also for his help in getting it running. Peter has maintained far more engines than I have, and his natural sense about what tools I would need next, as well has his quick solutions to problems I had no idea how to solve, were invaluable. Add to that a perfect sense of when and where an extra hand would be of use - something I am terrible at recognizing after spending so many hours alone in my shops - and you get an ingredient that made this six day restoration possible.

Second thanks goes to Becky, an absolutely wonderful host. From entertainment to nourishment, she kept our spirits high all week. Seriously, I wish I had written down all the delicious meals she prepared for us, because I would have loved to brag about just how well we ate!

We got by with more than a little help from other friends, too. Thanks to Charlie for sharing his locktite and enthusiasm. Thanks to Justin & Shannon for being so helpful and flexible with temporary storage plans for the bike and its parts - and for a wonderful evening catching up. Thanks to Adam for a brain dump of so many small-engine repair ideas - from problems to watch for to tools to have on hand - and for the little green screwdriver with the magnet in the end, that saw more use than any other tool!

I can't thank them by name, but the strangers along the way get shoutouts too. I think especially in these days of political divide and pandemic isolation, it has been hard to see strangers without heavy skepticism. In fact, I was quite worried about leaving the motorcycle parked in a hotel lot while we went to reunion for three days. But despite story after story online about this being the exact scenario most likely to result in damage or theft, as far as I can tell not a single person so much as leaned on it. Everyone we met along our path was the most helpful, friendly sort one could imagine.

None of this would have been possible without people that have kept these machines running for decades already. MAX BMW and Vintage Beemer Parts were my sources for classic parts, and delivered on-time and within budget. Shoutouts to the likes of O'Reilly, Autozone, and Clymer as well, for continuing to stock general automotive supplies and information in an age when doing your own maintenance is becoming a radical act. Vintage BMW is a wealth of knowledge - from old manuals to notes on which modern oils fit vintage specs best, and people on the forums still around to guide us newbies. All the Youtubers I called out earlier provided hours of information, inspiration, and entertainment.

Thanks to the U-haul depot staff. I mentioned that I'm not a fan of U-haul, because of past experience. But the negative experience has always been with the corporate network as a whole. The people working at the local depots are always the most helpful people, who are actually quite good at the on-the-ground operations of renting equipment. Those folks, I thank very much.

Most of all, thanks to my wife Amanda. I've mentioned a couple of the times that she jumped in and physically helped me fix and move the bike. What I didn't mention was the dozens of times she supported me mentally and emotionally. Days of, “Should I really do this, it's really a bit of whimsy?” met with, “Of course you should. Whimsy is fun!” Hours of listening to me excitedly spewing nonsense about the latest oddity I had researched. And the calm, “We'll figure this out, or we'll figure out another way,” when sudden setbacks challenged my confidence. We married well.

Categories: Motorcycle Travel