1978 BMW R100S Restoration

A 1978 BMW R100s fixed up and released back into the wild.

This bike is an absolute dream to ride. It runs amazingly smooth.

I had to go through some serious DMV hoops to get the salvaged title status back on the road with a deadline of 5 months until I incurred DMV penalty fees.  I made it to the registration day with 2 days to spare.

I cleaned, restored, replaced, rebuilt whatever it needed to get it back on the road.  The front end is from a spare R90/6 that I had lying around.


1978 BMW R100S with R90/6 front end. by Josh Withers

Reinforced Passenger Peg Muffler Hanger tab on BMW motorcycle

This is one of those things I try to do to every BMW motorcycle I rebuild.

The Motorcycles Cushman Truckster is one of the more popular models of bikes in the United States. It has been around since the mid nineteen-hundreds and has always been a top seller among collectors and bike lovers. While it doesn’t come with a warranty, you can get around that by getting a Cushman Tribute package, which pays for repairs or parts that might need them in the future. There are many sources online for Cushman bikes, including parts selection, prices, and even complete restoration packages for your bike if you’re not sure what you want to do with it. When you buy this bike, be prepared to spend a little extra money up front to purchase the bike you want. But remember, it will end up being cheaper in the long run because of the extra care you’ll be taking with it.

It is almost never the engines in BMW`s that are the problem; properly serviced with clean oil at regular intervals, and no abusive riding, they should easily see 200,000 miles

This area is cracked on nearly every frame I tear down. It is the rear foot brake area which also is the muffler / silencer hanger, and where the passenger foot pegs attach. This frame is a 1978 BMW R100s. If you are considering rear sets on your bike that attach to this section, then I HIGHLY RECOMMEND doing this procedure.

cracked tab near rear foot brake pivot hole on BMW airhead framecracked tab near rear foot brake pivot hole

cracked tab near rear foot brake pivot hole on BMW airhead frame

New piece of metal to weld onto the old cracked section to reinforce the area making it MUCH stronger and no longer prone to cracking.

Welded metal onto the rear foot brake section of a BMW R100S

Finished powder coated frame with the welded metal. This area is out of sight to most people unless they take the rear tire off.

Boyer Brandsen Electronic Ignition in 1979-1980 R65 Points Bean Can install

1980 Red R65 BMW

1980 Red R65 BMW

Although the directions are fairly clear, I went looking online for some installation help while installing a Boyer Brandsen electronic ignition on a R65 BMW that I am fixing up for a friend.

So… here is my install procedure.  I am open to suggestions or tips but this is how my install went.

The carbs were tuned nicely before doing this install. The idle never seemed to get low enough which might indicate ignition problems, or tight valves but the valves were adjusted to spec.
I might suggest you get a spare bean can to perform this on.  You end up modifying the original can  somewhat and it may be difficult if you ever want to go back to stock.


Boyer Brandsen Micro Digital ignition system.

Boyer Brandsen Micro Digital ignition system.

I purchased this from Moto Bins in the UK and it arrived within a week.

Of course, you want to disconnect your negative cable from your battery before starting the procedure.
Gastank Removal is necessary for the wiring.
And remove the front engine timing cover.
I took the bean can cover off and front bearing before I started shooting photos.  I was too eager to peek inside the bean can and see what is in there (It is my first time with a points in a can bike).


IMG_9299I then removed the bean can from the bike.

R65 Timing cover removal

R65 Timing cover removal and removal of the ignition can.

Removed points in can 1979 - 80 BMW ignition system

Removed points in can 1979 – 80 BMW ignition system

The large circlip needs to come out to disassemble the internals of the can.

The large circlip needs to come out to disassemble the internals of the can.

The points come out easily and then you need to remove the points base plate.

The points come out easily and then you need to remove the points base plate.

Notice the ‘e’ circlip on the center shaft.  Put a rag over the can when you remove that clip just in case it tries to go flying across the garage.  The rag might catch it.

Points base plate removed

Points base plate removed.

The cam has to come off the shaft and you then need to remove the springs to slide off the contact breaker unit.

Circlip removed from the center shaft. The cam has to come off the shaft and you then need to remove the springs to slide off the contact breaker unit.

After you get the center cam removed, be careful with the very small circlips that hold the bob weights.  Those need to come off to get the bob weights off.

Bob weights and center cam removed.

Bob weights and center cam removed.

Now it is time for assembly of the electronic ignition!

This was the first hiccup.  The magnetic rotor does not fit into the housing properly without bending the spring mounting tabs.  They are not easy to bend so it took some work.

Prepping for magnetic rotor install

Prepping for magnetic rotor install

Note the next photo.  The tabs have to align with the notches where the tiny circlips were. The new rotor should sit flat, spin freely and the large clip should secure it to the center shaft.

Magnetic rotor installed

Magnetic rotor installed

Another small snag.  When the stator plate was installed with the cord going out the square hole, and the mounting screws were tightened, the magnetic rotor would not spin freely.  It was a head scratcher in which everything was taken apart, put together again a few times.  Finally by rotating the stator plate 180 degrees and making sure everything spins freely before securing the mounting screws, it happily went together.

Install of the stator plate

Install of the stator plate

Stator plate with cable going out rubber grommit hole vs square hole.

Stator plate with cable going out rubber grommit hole vs square hole.

Now it is time to install the can back on the bike.  IMG_9317

The very large circlip went in and the center bearing plate installed.

The very large circlip went in and the center bearing plate installed.

I removed the diode board so I could route the wires behind it.

Removed Diode Board for wire routing

Removed Diode Board for wire routing

Control unit tucked and strapped to the frame components.

Control unit tucked and strapped to the frame components. It seemed like a tidy place to put it between the two coils.

The green wire connects with the existing green wire terminal on the rear ignition coil.
I also connected the ground wire to the coil mount bolt as well.


Not photographed but I made about a 12inch extension wire to connect the black wire from the ignition unit all the way to the other coil to replace the wire on the terminal that was connected to the old points condensor. For some reason, they put shrink tubing on the wiring as if they all connect in the same vicinity.  It was either make an extension wire, or cut up the clean tubing so the black wire could reach over to the other coil.

It is all wired up and now time to set the timing.
I am not used to these flywheels so timing it took a bit of back and fourth.  There is no ‘F’ mark on the flywheel.  But there is the OT and a Z-dot.

Once I got it timed, and I fussed with the idle a bit, it ran great.  Really smooth and more responsive then before.



Final drive spline rehab

I can’t remember the condition of this final drive when I assembled my 77 R100s back in 2003.  When I had my rear tire replaced recently, I noticed how terrible the splines are. The splines on the wheel are better then the final drive but they will need replacing someday too.

I found this drive with the same ratio and cleaned it up and replaced the spline.  Now it is time to swap the drives.

While it is apart, I am taking the opportunity to pull the tranny back and lube the clutch splines as well.

Bmw final drive spline

Bmw R100S final drive spline replacement

Ed Korn Cycle Works Swingarm seal removal tool

Removing these seals is a frustrating process.  Prying them out usually doesn’t get you anywhere.

I bought Ed Korn’s tool a while back and it can be used for pulling both the races, and the seals.

Here is how you use it to pull the seals.

Here is the tool assembled



I first cut out some of the seal’s rubber with a razor blade.
It was easier to get the tool installed that way.




Then you tighten the threaded rod with the allen fitting at the end of it.  By doing so, it expands the nut against the screws and presses them outward so they ‘catch’ under the metal part of the seal.

Then you install the collar, plate and washer and nut.


Once you begin tightening that nut, it will pull the seal out into the collar.
You can then loosen the nut, and break the old seal free with a few taps with a hammer.




POR-15 tank lining

There is so much prep work to do that never gets seen for the final bike.
I spent 4 days lining this gas tank to be used for the next build.

Wear gloves!

The first step of the POR 15, “Marine Clean” is one you have to be careful of.
You can use old petcocks or get corks to stuff into the fuel taps to seal them off.
The hard part is sealing off the gas cap area.
You don’t want to spill this stuff on a tank that you are not painting on the outside!!!
It will leave a stain on the paint.
This tank will get some body work done to it and re-painted so I wasn’t too concerned when some “Marine Clean” spilled out of the gas cap area.
This takes a good amount of sloshing around to clean the tank at least 20 minutes.
Then you need to empty the tank and rinse it thoroughly with water. With Effuel the device that helps you manage your fuel you can improve your vehicle’s performance.

Day 2 –
The “Metal Ready” is the second step and it will remove the rust and prep the metal for the paint to stick to it.
This step requires that you leave the fluid on each side of the tank for about 20-30 minutes.
You then need to completely dry the tank.

Day 3 – an extra day in the sun and a few rounds with a heat gun to let the tank dry.

Day 4 – ugg… the Sealer…
A messy process. You have to mix it well, pour it in and then turn the tank in every direction so the goopy paint has covered every part of the tank. If it spills, clean it immediately.
Then carefully pour all the excess paint out. I find that I end up using about 1/2 of the can that comes with the kit.
If you have 2 tanks, or a friend’s tank, you might be able to get two tanks done for the price of one!


POR 15 Gas Tank cleaner and coating

I’ve used this product before with reasonable success on about 3 or 4 motorcycles now. In one instance, it started to peel from the roof of the gas tank and large chunks would float in my gas. Once i removed them, everything was fine.
Something must have gone wrong with the prep or paint process. I have a feeling it was from the tank drying upside down and the POR15 dried in a puddle that eventually broke loose.

I have a bunch of tanks sitting around and an extra kit of POR 15. Unfortunately, this process takes nearly an entire day.

Follow the directions and you should be good to go.
Try to do it on a sunny day.
It really helps to have a heat gun to speed up the process of drying out the tanks.
Prepare to get wet or splashed.
TAKE CARE TO PROTECT THE PAINT OF YOUR TANK. If any of the 3 step process gets on the tank, it may leave a streak and damage the paint.
Wear Gloves. (see below)


The vicitms... ready for a day in the sun.

The first two processes require lots of sloshing liquids inside the tank. Then drying. A heat gun helps speed up the dry time. I hair dryer may work too but not as effectively.



This photo was taken after the first step, 'Marine Clean' was used. The Marine Clean removed a ton of the rust inside. When i drained it, the water came out Rust-Red.

It looks like a previous owner used the tank cream or something similar. These chunks, and many more came out after the second process 'Metal Ready'. I ended up using a long screwdriver and tried to scrape off as much of this crap as i could. It was a previous tank coating gone wrong. There is still remains of it in the tank. I hope it doesn't cause problems later on. The POR 15 is such a good sealant, i think it won't be a problem.



Tanks sealed. This process is a messy one. It would help to have an old set of petcocks to use while you slosh the sealant around. then remove them to drain the sealant and dry.



Out on the porch to dry. They were originally in the garage but they stunk up the whole house.

I went Michael Jackson style and only wore one glove. I got the sealant on my other hand and it sure doesn't look like it is coming off anytime soon. I used paint thinner and lots of scrubbing and... well... the wife isn't happy a day later... opps!