Repair Stripped Cylinder Head Stud Threads in the Engine Block

The first sign of the problem was this bike would not idle well. I thought the carburetors got dirty and all I needed was to clean them. But, before I started on that task, I decided to check the valves and I found the left intake valve lash was 0.012 inches instead of 0.004-0.006 inches. Hmmm …. how did that tappet get so loose?

Before I reset the valve clearance, as I always do, I torqued the cylinder stud and head bolt nuts to 25 Ft/Lbs. But, one stud just spun.  Bummer. That means the threads in the engine block are stripped.

It turns out a friend of mine, Dick, had the same problem on his 1972 R75/5 a couple of weeks earlier. I contacted him and learned he made arrangements to rent a jig to repair his stripped threads from Northwoods Airheads. So, we jointly repaired our stripped threads in “Brook’s Airhead Garage” when the jig arrived.

This write-up is based on the work we did on both bikes.

Here is a link to a video of how to use the Northwoods jig to drill out the damaged threads, tap new threads for a 20 mm long M10x1.5 Heli-Coil insert, and install the insert.


“Motorcycles and Other Musings” is Now “Brook’s Airhead Garage”

I started this blog back in 2009 as a general blog space with the original name “Motorcycles and Other Musings” to cover the expected content. As is often the case with an idea, it takes it’s own course and becomes what it is meant to be.

This blog is 90% about BMW Airhead motorcycles I’ve worked on in Brook’s Garage which I had built in 2012. SO ….

I changed the name of the blog to better reflect what it has become over the past 10 years.

Same content, same author, same passion for helping amateurs keep their classic BMW airhead motorcycle(s) running smoothly.

I also updated my YouTube channel to use the same name.

–> Brook’s Airhead Garage-YouTube Channel

I have created over 50 short videos that are used in the documentation of the various rebuilds I have done. The number of subscribers for my YouTube channel is just about the same size as for this blog.

And, I’m starting to plan for another restore/rebuild project soon. The bike is a 1983 R100RS. I may do a “resto-mod” on this bike, or I may not. I’m still thinking about the direction I want to take.

Stay tuned …



Musing: The Luxury and The Misery of Time

Shortly after I started riding motorcycles, my bike became my only motorized transportation. Consequently, if I had to work on the bike, I had to finish the work or I got to walk. For awhile that work was done on the street by the curb in front of my apartment. It was never much fun, particularly when it was cold and windy.

Any work I did had to be completed “sooner rather than later”. If I hadn’t gotten all the parts I needed to do the work, because something unexpected was really the problem, or I broke something, I had to find a way to get to the dealer. More than once, I put the bike back together, rode to get the part I needed, then rode home, took it apart again and installed the part. The misery of time is nurtured by the need to “be done” and invigorated by having to work in the cold.

Another way to experience the misery of time is when the bike dies in the middle of nowhere. It was a cold Sunday morning on I-10 just past Wilcox, Arizona when the center cylinder of my Kawasaki S2 350 triple seized as I drafted beside a tractor trailer as I tried to get warm. The dead air cut the wind chill by 20 degrees so I could start to feel my fingers again.

A 1972 Kawasaki S2 350 Triple Just Like Mine

I avoided hitting the back of the trailer or going under it when the rear wheel locked up, so that was good. But as the truck receded into the distance, I was on the side of the road with no idea how I was going to get to work 200 miles away in Las Cruces, NM, by noon.

No cell phones in the 1970’s so I had no way to call the manager at Denny’s to alert him of my problem or to call anyone to come trailer the bike. Fortunately, after the engine cooled, the center piston ring broke free when I kick started the bike. I rode on the shoulder of I-10 for a never ending 200 miles to get home. All the while, I listened to every noise the engine made for signs of another impending seizure. This form of time misery is akin to slow, never ending Chinese water torture. Every second seems like a minute.

It took a week for the dealer to get the bike running again, so I walked the 1.5 miles to work and back. Being a starving student, I didn’t know if I could pay the bill, but I got lucky as it only cost $25.00 for a hone and new rings on the center cylinder.

Moving forward about 45 years, I’ve completed three airhead rebuilds so far. The first two took as long as they took with no pressing need to be done. I greatly enjoyed the experience and indulged my curiosity so I could learn what I didn’t know. I could take things apart and reassemble them a second time, if need be, in order to get it right.

I have a heated shop so cold and wind aren’t a factor. When I need parts, I can wait for them to arrive. And I don’t have to walk everywhere until the work is done 🙂  These rebuilds had the luxury of time so they were invigorating and joyful experiences.

But, the last build, a 1977 R100RS, had a deadline. I had no more than one year from the date I started until I had to be done so I could ride the bike to the 40th RS anniversary in Pennsylvania. When I found problems I hadn’t anticipated, which is par for the course, they added to the anxiety as several of them required outside services I didn’t control to do the work for me. Their schedule was not my schedule.

My Last Build, 1977 R100RS, on a Shake Down Ride to the Coffee Shop

A Shake Down Ride to the Coffee Shop on My Last Build, 1977 R100RS

I made the deadline, but in all honesty, for much of that build, the work was not very joyful. Many times that year, I had an old, uncomfortable feeling I couldn’t put my finger on. Then it dawned on me. I inadvertently invited the misery of time to come join me in the shop as soon as I set the deadline.

This is a good reminder to me to let the work proceed at it’s own pace and not worry about hitting a deadline. This is how you train time to become a joyful luxury instead of a misery.


Musing: The Joys of Being A Minimalist

A minimalist is someone who follows this creed,

“Everything should be made as simple as possible, but not simpler.”, A. Einstein.

It is a “scientific” creed similar to Occam’s razor summarized as, “The simplest explanation is usually correct.” These two guiding principles provide direction when you are looking for explanations and aren’t sure how to proceed. But, they also underpin a philosophy of design that creates unadorned, straightforward products that are a delight to experience.

My appreciation of BMW airhead motorcycles is a practical expression of Einstein’s prescription of what the result of science should look like. Airhead design is functional, not elaborate nor flamboyant. The styling relies on form following function for its appeal, not on plastic panels and extraneous amenities that distract from the direct understanding of how the machine works. Even when BMW introduced the first motorcycle with a manufacturer integrated full fairing in 1977, the R100RS, the shape of the fairing was defined by aerodynamic necessity and the requirement to protect the rider from adverse weather. I think the RS fairing is a design that solves several hard problems as simply as possible, but no simpler.

For BMW airheads, the art in the design lies in engineering control of material properties and precision machining during manufacture. For example, machined tapers with press fits are preferred to castle nuts with tab washers when connecting driven components on a turning shaft. Parts inventory is minimized and the assembly procedure is simple.

Another example is the tool kit that comes with the bike. With it, you can disassemble just about anything on the motorcycle. I’ve used the tool kit to remove the top end to replace rings and then reassemble it. I have removed the transmission, the drive shaft, the entire rear sub-frame and the rear wheel with it. Nothing else in my tool box was required. That lowly, hidden tool kit is an elegant expression of the minimalist mindset.

The joy of motorcycling comes from a direct, frictionless connection between mind and action, but that is deepened when the machine you are riding is an elegant execution of the minimalist creed espoused by Einstein.

I think that’s why I got so involved in airhead wrenching over the last decade.

Airhead Electrical Systems Documents

I put together a series of pages about BMW airhead motorcycle electrical systems. It strikes me that electricity in general, and motorcycle electrics in particular, are dark mysteries to many, so I thought I’d shine some light [puns intended 🙂 ].

Lack of understanding hinders confidence when diagnosing and working on electrical projects. As these bikes age, the electrical system is prone to problems as corrosion and neglect makes them behave badly. More owners are having more electrical problems but seem less able to get to the root cause of the problem.

I think one tool that many avoid using is the wiring diagram. The spaghetti of lines, symbols and notations makes the eyes glaze over. “Oh goodness, where do I start?” is the common response to the advice, “Look at the wiring diagram.”

5 Series Wiring Diagram (1970-1973) (Source: Haynes Manual) –> CLICK TO ENLARGE

I’m not an electrical engineer, but I have taken time to learn the basics, have collected comments and input from well respected airhead mechanics and dug into how BMW applied electrical theory when they designed the /5 electrical system. I’ve learned a lot from various reference sources that are scattered about the internet, so my articles include a bibliography of various useful resources. That way both you and I have a nice set of reference materials to consult when problems come up.

I have published three articles (so far), Basics and two about the /5 series: 5 Series Electrical Circuits and, 5 Series Electrical Components. I chose the /5 series to start with because I believe it’s the most popular airhead series for restoration.

I hope to write an Electrical Circuits and Electrical Components document for the /6 and /7 series up to 1984.

Here is the table of contents from the first three documents.

Airhead Electrical Systems-Basics

Airhead Electrical Systems-5 Series Circuits

Airhead Electrical Systems-5 Series Components