Ross Kowalski's Beemer-Chang
I purchased a BMW-powered CJ recently. It is really nice with an R75/6 engine, electronic ignition upgrade, LED lights and flashers, M5 wheels with aluminum rims, Avon sidecar tires, a leading link fork, powder coated frame and more. I am redoing it to my taste. (FYI, this isn't one of Jim Bryant's conversions.)
Here is the bike dressed out by the previous owner.
A friend and I went up to Cambridge to get the bike. It was supposed to rain so we took his van.
My friend helping disassemble the bike for transport in his van.
The bike stowed against the front seat and strapped to the sides.
The sidecar was full of all kinds of goodies - manuals, spare parts, helmets, oil. A pleasant surprise.
We wheeled the hack up a wooden plank with plenty of room to spare.
A shot of Bob and me with the bike.
The bike out of the van and reassembled back in carver.
Bob test riding the bike. See it on Youtube here.
The spring mount on the new bike, notice it is a weldment and has only seven leaves.
For comparison, here is the mount and spring pack from my black sidecar bike.
I noticed a crack in the dust cover behind the sidecar hub.
Conveniently, the welder was already out because it is harvest time for cranberries and the equipment is getting prepped.
I cleaned the paint from the crack with the needle scaler.
A shot of the completed weld.
There was some sandable gray primer, so I used it, though black paint would have been my first choice.
I took it off later becuase I noticed that the spring bump stop was at the end of its traverse.
Here is the bump stop bottomed out.
I pulled the spring pivot arm and found that the problem was that there was no torsion bar.
Adding a new fender support at 90 degrees to a fender freshly stripped, frenched, and primed.
The rear fender pulled and stripped.
The package rack mounting holes.
The package rack holes welded over.
The sidecar, rear fender, and sidecar fender, stripped and the front fender stripped and painted, and the gas tank stripped frenched and painted.
Part II
The sidecar tub with all the bondo removed. I welded the holes and dollied the metal flat again. I also rewelded any seems that looked questionable or incomplete.
Here is a picture of the sheetmetal primed and ready for sanding.
Part III
The pivot shaft for the sidecar was seized so I pulled it, cleaned it up, and greased it. It moves flawlessly now. I didn't get pictures because I didn't want to touch my camera during the greasy and nasty proccess.
I put the replacement sidehack suspension torsion bar in last night. Went perfectly which is more than I can say for the pivot arm.
Part IV
Sidecar toe-in was 3" out but it was adjusted as far in as it could go. The tires were centered and the frame straight. Hmmm.
I checked the axle and it was in plane with the sidecar frame. I pulled the rear mount and found that the rear adjuster was actually bottoming out in the frame against the torsion bar mount. Hmmmmmmm.
I took a break to finish welding the ignition and light holes on the headlight and fillet the mounts.
I cut 1.25 inches from the end of the rear sidecar mount. It is some seriously thick wall steel tube.
After putting it back I could adjust the sidecar toe-in properly.
The rear strut was adjusted all the way in when the bike was at the proper lean so I ground the weld off of the bottom end.
I twisted the pipe off of the fitting with a pipe wrench.
The fitting removed from the strut.
The length of the tube was 11 inches.
I cut a slug off of the end with the bandsaw.
The walls of the strut pipe are thick wall as well.
The strut in the lathe.
I cleaned the baked coating off of the outside, beveled the outside in preparation for welding, and counterbored the inside to fit the fitting.
I used the giant brass hammer to "press" the fitting into the rezied strut.
The strut 1.25 inches shorter.
Welding the strut with the mig welder.
The strut after removing the powder coat burned from the welding.
The bike now easily adjusted to the proper lean.
Some battery strap brackets bolted to the rear sidecar mounting bolts.
Part V
I never liked the idea of venting the transmission out of the speedometer hole so I made up a plug for it using an o-ring from some kind of fitting in the air fitting drawer.
A sketch of the electrical system.
A sketch of the charging system for the BMW R75 engine
I didn't like the rear profile or general design of the OEM BMW engine top cover so I am making up a replacement out of an old 6" aluminum water pipe. The OEM design had the air intake pulling in some air from the alternator cover to help cool it. I might add a little fan in there later.
It would be nice to package the coil on the engine so as to minimize the wiring from the engine, but it is nicer to keep the coil cool. I am making up a mount from " aluminum to mount the coil on the frame electronics box mount.
Part VI
The stainless bolt that was used on the brake lever was threaded it's entire length so that it would wear quickly. I cut down some 1/4 x 20 bolts and drilled out the mounts and levers.
The bolts installed on the brake levers.
I installed two 15A circuit breakers, one for the ignition and one for the lighting. I added the second breaker so that if there was a short in the lighting circuit the bike wouldn't stop.
I made up a short rachet strap for the battery case.
The left switch assembly for the cj is pretty odd and cheap. I got a 2007-8 Honda switch off of eBay.
To open the hole up from 7/8 (I think) to 25mm, I made up a knurled shaft to use as a ream.
The modern left hand controls fit to the left bar. I might put a set of Grand Turismos on if I can find some.
The coil bracket getting fitted up.
Part VII
I missed a few days of documentation in the BMW-Chang refit. Not documented: taillight and sidecar marker light installation and wiring, ammeter installed in headlight nacelle, 12V and ground bus bar installation, rewiring left grip, high beam relay install, rear brake switch installed, final charging circuit wiring.
The end of the main grounding wire for the headlight bucket.
Cutting a clean end.
Scoring the insulation .
Pulling the insulation off of the wire.
Notice the wire is tin plated copper. I use this because it will not corrode even if the insulation is compromised. It is slightly more exotic so if you buy it the cost will be greater, and if you scrounge it you will only be able to find it on higher quality machines. I rewired the left switch because it only had insulated copper wires.
Pulling the insulated collar off of the terminal. I didn't have a "yellow size" fitting which would have been the "correct" one, but it won't matter when it is soldered.
Adding a little water soluable flux to the end of the wire only. It gets wicked through when the wire gets hot and makes less of a mess. Also, tin plated wire almost does not need to be fluxed.
After crimping on the terminal, it is soldered. Though not pictured because I couldn't hold the camera and solder.
The heat shrink tubing being shrunk in place. I normally use the clear stuff. My wife makes brass and steel mounting hardware for art at the gallery where she works and has a giant roll of the stuff. It is much thicker than the standard small gauge electrical wire heat shrink.
Airplanes use high quality terminals, crimped, checked with a go-no gauge, wired into a professionally designed loom, laced, inspected, maintained, run in a plane that turns int a narrow RPM range, and enclosed from the weather. None of that's true for the things I usually work on. Badly terminated wires are a source of trouble so make them solid.
The ground bus bar installed in the headlight nacelle.
The headlight relay wire is too thin to get reliably connected to the power bus bar.
Crimping a splice tube on the end of a fluxed wire to give it some meat.
The serious dimple in the middle of the crimped connection. Next it will get heated to flow the tin from the tube with the tin from the wire "soldering" it together as well.
I started cleaning the headlight ring only to find it was made out of copper! I stopped and threw it on the scrap pile. I looked closer and saw that it was hand formed. I have a hooded steel one left over from the LED project that will get installed. Maybe I'll add the 1800 lm LED headlight to this bike. Hmmm.
The mounting tab at the bottom was steel and spot welded on. I didn't even know you could spot weld copper to steel. It broke off so I guess it doesn't weld very good.
Out came the the side plate casting stuff box. This bike is going to need some sideplates. This is a good excuse to make some more because I still get requests from time to time and don't have any around.
The old pine 2 x 4 mold backing.
Two newly surface planed oak mold plates. The oak had to be ripped and planed because it was a broken 2" x 3" trailer stake.
The surface planer apparently has met some nails in its lifetime. Nothing a little sanding won't fix. The faces of the mold plates get heavily reworked anyway before use so no problem.
The mold plates drilled and cut.
The hold and parting lines singed to remove water from those areas.
The silicone mold for the left sideplate.
Brush out the sawdust and accumulated dirt.
A little talcum powder. I didn't have the "real" stuff (pure) so I used J&J baby powder even though it is heavily perfumed. The talcum gets brushed out over everything especially the the air vents, the pipes, under the gate, and the flats.
The mold on the cookie tray to collect spilled pewter.
The oak/silicone seam. It must be perfect to prevent metal from flowing out.
The oak/silicone seam has a little help being closed by some heavy steel bars on the top of the mold plate.
Skipping a whole bunch of steps because I was busy melting and pouring metal, here is the gate filled with pewter. I'll be casting more and will get some shots of the missing steps then.
A shot of the brake light switch (industrial limit switch) I installed on the right rear footpeg mount the other day.
These switches allow you to change the orientation of the head after installation so I changed it to vertical after this picture was taken.
The brake lever unscrewed for a minor adjustment. The lever apears to be forged so I will have to heat it pretty seriously to move it and I don't want to heat the shaft as I suspect it is heat treated.
The weather has been nice so I have been away from the bike, but I did get the bike wired, the lights finalized the sideplates cast, and a few other things.
One of the seat bolts did not line up with the mounting hole in the hack.
With the old bolt removed a mark can be made for the new hole.
The sidecar light is a blueish LED. The covers are canvas. I may take the sidecar cover apart and make up a set of plans.
The gas tank is not the final one but a primed spare I had around from another project. I have it on there just to hold gas, which it barely does having a crack along the back of the tank This is why I removed the toolbox from the tank that I am using on th bike.
My "new" ammeter. The speedometer is a custom digital affair which will be documented by itself for the toolbox.
The horn is mounted to the headlight nacelle with access to the wires and adjusting screw. The turn signal stalks were shortened.
The rear turn signals were relocated to the stop light bucket. Also visible is the wiring bundle running along the outside of the fender.
A close up of the avon sidecar tires which are very square in profile.
The square profile really does seem to work better with the sidecar, though I might change my opinion after I put some hours on the bike.
More to come......
Part IX
A new hole for the sediment bowl/petcock.
The reinforcing plate is 1/4" thick to accept some threads.
The original hole plugged. I normally would have welded it closed, but I might use it for a quick drain.
The fuel petcock hole temporarily plugged for tank sealing.
The original filter hole diameter.
The outlet hole with flare fitting.
The inlet hole diameter after removing the inlet tube.
The filter hole enlarged.
The outlet hole cleared.
The enlarged inlet hole.
A test fitup of the petcock/sediment bowl.
The front brake mounting post. Note the dimple which is all that secures the post.
A shot of the new mounting post mounted on the sideplate.
The brake cam spaced inwards.
A shot of the brake pads spaced inwards for the M5 wheels. It looks like the pads will need a sanding as well.
The locating post now has a hole in it that will secure the new brace.
The almost horizontal angle of the leading link suspension "fork" rotates the brake backing plate almost 90 degrees. This makes the stock brake cable barely reach.
A brake locating post locking arm layed out on some 3/16 inch steel.
Making the ends rounded.
A .56 hole fits the .550 mounting post perfectly.
The new brace sitting on a layout sketch.
The brace in position, notice that the brace is attached to the shock mount and pinned with a spring clip.
The new brace rotates the brake backing plate to almost it's original position putting a little slack back into the brake cable.
Part X
Getting back to the bike after a few busy weeks was a chilly but refreshing change. Some electronics came in so I figured I would get to the turn signal indicator LEDs.
Some electronics for the digital speedometer and the indicator lights.
Drilling the pilot hole for the led turn signal indicator.
A little silicone on the LED holder to keep the rain out.
The bulb ready to install. I used white LEDs for visibility.
The sidecar marker lights are attached with metal tabs bent under the edge of the bezel and then extra secured with silicone. The fusion tape on the back of the bulb holds the wires out of the way for easy installation.
The tank, while dented and far less then perfect, has no bondo on it whatsoever. I'm not sure I can fit the sideplates unless it warms up.
Part XI
Got a few things done on the bike today and did have a chance to make up the final list of things that have to be done.
  • make speedometer and tach
  • oil pressure light
  • charge light
  • highbeam indicator
  • mahogany duckboards
  • front brake arm 9mm nut
  • reshape rear brake lever
  • rear fender lower bolt
  • paint rear shock covers
  • air cleaner

I hope to knock a few off of the list tomorrow.

Cutting the flattened reverse lever.
Reverse lever temporarily mounted, but more to happen there.
The petcock in position with the gas lines back on.
Shot of the bike with the tank on.
New sidecar fender taillight mounted with hole to be filled in fender.
A Walmart fishing dry box for tools in the trunk.
Part XII
Finally got back to the BMW-engined Chang today. I am fitting a steering damper so I did some measuring to see where best to put it. Of course I noticed a few other things so I got started on those as well. the wheel.
The steering damper length is 10" eye to eye.
The steering damper extended length is 13" eye to eye.
One end has a Heim joint with a metric bolt of some kind.
The other end has a fitting for a 10mm ball stud.
The damper will fit the lower triple tree plate.
With the steering centered and the damper centered, the locations look good. I'll have to make up a ball stud and bracket to do the mounting.
Two holes marked for the engine top cover hold-down system.
Checking the location of the clip for the top cover.
Some rivets poking through the top cover. It is made from old 6" bog irrigation pipe that gets pitted from the acidic iron rich water in the area.
A copper hammer stood in for a riveting buck.
The formed rivets on the clip.
Drilling the mounting holes for the lower part of the clip.
The left top engine cover hold down.
A little look at the steering geometry. There is some measurable trail in the system. Not much there, but trail is like money. You need at least some. Also, the fender is not doing much for me. I think I will take it off and tighten the radius to more closly match the wheel.
I found some 10mm ball studs for the steering damper this afternoon on a 250lb nitrogen cylinder in the shop. I figure they should be stout enough for the job. My plan today was to figure out what to do about the no steering trail issue so I pulled the front wheel and fender to get a better look at the forks. I need to throw more thought at that problem so I figured I would mount the steering damper.
I found two ball studs so I have an extra if I decide to mount a damper on the other bike.
I decided to mount the damper with the piston end up to keep sun and rain off of the seal. The upper mount was drilled through and bolted.
I rechecked the location for the mount before filing off the powder coat.
The bracket was made from 3/16" steel sheet.
The final shape layed out in pencil on the sheet.
Roughing out the mounting bracket.
Checking that enough powdercoat was filed off.
The leads from the welder just reach across the Clydsdale-proof barn door being assembled in the main bay.
I had to steer the bike into ground clamp range with the jack on the front hack mount.
Pulling the ground from the battery and turning the battery isolator switch as a precaution.
The lower bracket tacked into place to check for proper movement of the damper.
The bracket welded into position.
The damper in position.
The position of the damper with the front wheel back on. I'm not sure what the best damping level is, but you can definitely feel the damping action.
More to come...