Over the Memorial Day weekend, I took on the task of rebuilding the carburetors.  The right side carb had a broken float pin boss and I had to get a used R75/5 carb body 5 years ago to get it running again.  The right side has not been happy and when the heads and valves were redone, the right side exhaust was in worse shape than the left which are signs of lean running on the right side.  With 103,000 and 35 years on the left side carb, and no full rebuild in that time (new floats and float needles of course, but no rebuild) it was time to get them back in condition.

To keep parts together, prevent confusing the parts from the left with those from the right side and to always have a correctly assembled carb to refer to, I rebuilt them one at a time starting with the right side.  Since I was going to reinstall the original 75/6 right side carb, I would be stripping all parts off the old 75/5 carb body, replacing with new parts in the rebuild kit, and reusing the other parts.  The R75/6 body had been sent to the Bing Agency to repair the broken float boss.  Here are the before and after pictures.

Although Bing cleaned the carb, I polished it up a bit more with aluminum cleaner, steel wool and metal polish while I waited for parts to soak in solvent.

The first step was to remove the enricher from the R75/5 body taking out the 4 machine screws.  As you can see in the picture, this is the Bad part — as in dirty.  But it gets worse.

Next, I took off the float bowl … and now you can see the Uglypart … a nice bunch of glop in the bottom … not a good sign of a healthy carb by any means.  I’m suspicious that the float was starting to dissolve which can happen with our methanol laced fuels.  Corrosion is also clearly evident on the washer underneath the main jet in the center of the carb and the gasket between the float bowl and carb body is complete toast.

I focused on the enricher rebuild first.  I dissembled it, and took pictures of the parts order so I wouldn’t make a mistake.  I also have the Bing Agency carb book with full exploded view diagrams which is very helpful.  I’ll refer to part numbers in this diagram in the following material.

I removed the old O-ring (pretty cracked) (#26) and soaked in parts washer solvent for several hours.I cleaned up the housing and lever using a wire wheel, aluminum cleaner and then metal polish.  I used some masking tape to cover the threads of the disk (#47) to make it easier to get the O-ring (#49) on and not tear it in the process.  I have some steel picks, one of which has a “C” shaped end that I hooked under the O-ring so I could pull it over the threads and onto the slot.

I found details in Snowbum’son-line BMW reference material on how to ensure the enricher is assembled correctly.  There are two articles as well as another on the R75/5 Bing carburetor.  As is the case with his writing, read slowly and carefully and be prepared to be told the same thing three times in different places and different ways.  The right side housing has the curved passage on the right.

You should confirm you have the correct disk.  The inside of the shaft is stamped with “R” for right and “W” for wrong … :-), actually, it’s “L” for left.

Then the disk is inserted as shown, with the slot at the 8:00 position and the little holes at the 1:00 position.

Then I assembled the housing putting the new gasket (#50) between it and the carb body.  I put a small amount of silicone grease on the O-ring and a tiny amount of antiseize on the threads of each of the screws (#51).  Note there is a dimple on one side of the shaft.  This should be closer to right side on the right carburator.

The handle goes on the shaft with the nut (#52d) to attach the choke cable facing you. The shaft handle goes between the two verticle pins and the shaft should be pointing to the fuel spigot on the carb.

I put a tiny bit of antiseize on the brass threads of the shaft and then tightended up the nut.

The next step was to remove the throttle linkage (#27, #28), spring (#35) and throttle linkeage bracket (#31).

Then I remove the throttle plate (#23) and throttle shaft (#24).  The screws (#25) holding the throttle plate to the shaft are peened over and are hard to remove.  I was not able to remove one of them.  So, I ground off the end of the screw on the back side of the throttle plate with a grinding stone on the end of a Dremel tool, and drilled a pilot hole for my smallest easy out and extracted it.  The carb rebuild kit comes with new screws, so no worrries.

I soaked the parts in solvent for several hours and then cleaned them.  I polished the throttle linkage parts and springs with a wire wheel, steel wool, aluminium cleaner and then finished them off with metal polish.  I replaced the O-ring on the throttle shaft using tape over the threads and put a bit of silicone grease on the O-ring.  Then I pushed the shaft back into the throttle body.  It took a couple of tries to get the throttle plate into the slot in the shaft, so be patient and don’t force it.  I found assembling the throttle linkage bracket (#31) into the groove on the throttle shaft and then tightening the bracket screws to the carb body ensured the shaft would not bind.  I didn’t do that the first time and it bound up as there is some laterial play in the throttle shaft.  I used lock tight on the throttle plate screws to ensure they wouldn’t come loose … if they do, they go right into the engine 🙁  I also put a tiny bit of grease on the groove in the throttle shaft to keep things turning smoothly.

Next I removed the top, pulled out the slide with the jet needle and removed the metal ring (#17) holding the rubber diaphram to the top of the slide.  There is a new jet needle (#3) in the rebuild kit and a new needle jet (#4).  The needle vibrates and wearing the needle jet and the needle.  I could see grooves in the needle.

Then, I took out all the jets from the bottom of the carb.  When I reassembled the main jet, it cracked in two.  It likely had a crack in it before hand.  I suspect a cracked main jet didn’t help carburetion any  🙁   I have extra main jets, so no problem.

Each of the jets I removed (#7, #5, #1, #2, #3, #10) was very dirty.  Here is the crud that was inside the needle jet (#3) and the atomizer (#2).

I had read on Snowbum’s posting that Berryman B-12 Chemtool was very good at removing crud and fuel varnish, but extremely nasty stuff.  I bought some and wore my nitrile gloves when handling it.  When I fished the parts out of the container, the nitrile started to wrinkle … the next day, the finger parts had completely dissolved … nasty indeed.

After all the internal jets were cleaned, I put new O-rings on them again using the masking tape trick and “C” shaped steel pick to pull them into the groove on the jets.  I broke one O-ring, but my handy Ace hardware had a metric replacement :-).  I put a tiny bit of antiseize on the jet threads as they are brass and screw into pot metal threads.   I installed the new needle jet (#3) and atomizer (#2).  The Bing exploded view diagram and the picture I took helped me make sure these went together in the right order.  I installed the new float (#40), float needle (#4) and float hinge pin (#1  from the rebuild kit and then put in the new cork gasket (#46) into the groove in the bottom of the float bowl.

I reassembled the slide (#13) with the new diaphram (#16) from the rebuild kit putting a dab of antiseize on the screws.  I added the internal spring (#22) which was not part of the original carb assemble.  Clem supplied these and said adding them would improve gas mileage.

Then, I put the top (#20) back on and put a tiny amount of antiseize on the four screws (#21) that secure it to the carb body.

Now for the Good part.  Here are “before” and “after” pictures showing the rebuilt right side carb and the yet to be rebuilt left side carb.  Definitely night and day.

I did it all one more time on the left carb.  Both were in need of attention, so I am very hopeful they will operate much better and the bike run a lot smoother.

The past week I’ve been working on a number of items.   First order of business was to put the shocks back together and mount them.  I clamped the shock in a vice an put the preload adjuster, retainer and shock together with the tighter windings of the spring at the bottom.

In lieu of the BMW shock spring compressor, I use  two 1 inch hose clamps to compress the springs so I can put the top shock mount bracket on.  Thread the hose clamps through three of the spring coils near the top and then tight to compress the springs leaving a clear space between the top of the spring and the bottom of the mounting bracket.

I could push the aluminum cover down a bit more to insert the 10 mm wrench on the shock rod and a screw driver through the eye bolt to tighten the top mounting bracket.

To mount the shocks, I used a jack stand and some wood blocks to hold up the rear end so I could insert the top bolt on the right side shock.  Since that side has a stud for the bottom mounting, its easier to mount the right side first.

With the rear shocks mounted,  I took apart the instruments, controls and handlebar to clean them up.  I also needed to remove the Windjammer V wiring harness from the headlight shell so I could reinstall the original headlight wiring harness.

I painted the headlight “ears”, and cleaned and polished the mounting hardware before putting the R90S turn signal brackets and fairing mounting brackets on.

I wired in the turn signal wires and the old front headlight wiring harness and the neutral switch that allows you to start the engine when the clutch is pulled in.  I took some time reviewing the wiring diagrams to find out where the connectors go inside the headlight shell.  I also had to modify some of the connectors to the correct “L” shaped connector with insulator boot. It does look like “wiring spaghetti” inside the headlight shell 🙂

The final task was to mount the speedometer/tach, handlebars, controls and atach the new throttle cables and the existing clutch and front brake cables to the levers.  It took some time and couple of disassemble/reassembly tries to get the wiring and cables routed correctly.  For some reason, its too easy to get one thing going the wrong way with that many cables and wiring harness to contend with.  Here’s the final handlebar and control assembly’s mounted.   The new paint stands out compared to the dulled plastic of the switch assembles.  I’ll try more Amour All and see if I can brighten the plastic on the controls.

At this point, the engine top end, carburetor rebuild and new electronic ignition installation are the remaining mechanical tasks.  And,  the painting project of course, is still left to be done.  But, the Silver Ghost is coming back together.

When I had the front end rebuilt, I had 11 rib fork boots not the standard 13 rib.  So, I removed the tubes and mounted the correct 13 rib boots.  I also cleaned up the snowflake cast front rim and the disk brake rotor assemble and had repainted the brake caliper which was showing aluminum instead of the original black paint.

Here are the pictures of the front end with the incorrect 11 rib and the correct 13 rib fork boots.  It looks much better with the correct ones installed.

I loosely mounted the fork brace and then mounted the front wheel .  I pushed up and down on the forks a couple of times to ensure alignment and then tightened the axle nut and locking bolts.  Again, I pumped the front forks up and down and then tighted the fork brace bolts to the correct torque settings.

I bought new disk brake pads and also had to buy a new brake pipe as corrosion had made one of the nuts too small to fit a standard 10 mm ring spanner.  The two pads are different.  The one that goes into the piston side (right one in the photo) of the caliper has a small hole in it and the fixed pad (left one in the photo) has two raised castings that center the pad in the circular caliper cut out.

The brake pad kits come with a new O-ring that goes inside the center of the caliper piston as shown and a new clip for securing the fixed pad onto  the back of the caliper.

Insert the pad into the piston first. The curved end of  the pad goes to the back of the caliper.  Then, put the pad into the fixed side of the caliper and secure it with the clip on the back with the open ends facing down as shown.

Next, I mounted the caliber to the fork using the excentric pin to hold it in place.  Finally, I connected the new brake pipe to the braided steel brake line.  Here’s the completed front end and wheel with brake caliper.

I spent a couple of hours polishing the aluminum engine cases with Autosol metal cleaner, metal polish and finished up with Aluminum oil.  Now it really matches the transmission and rear drive and has a nice satin patina to it.

Finally, I mounted the subframe. I found mounting it using the bottom bolts first makes it easier to force the top legs into the top of the spine.  Then I used a piece of wire and threaded it through the rear hole to the front hole in the subframe.  I wrapped the wiring harness with duct tape and twisted the wire around that and pulled the wire harness back through the subframe tubing to the rear.   Its all ready for the rear turn signals, but I have to finish painting the rear fender before I can mount them as they attach to the fender.

Here’s the Grey Ghost with the subframe mounted to the frame along with the key lock and the side handle for lifting the bike onto the center stand.  It’s starting to more like a motorcycle. I just need to slap the rear shocks back on when I get the chance.

We have had miserable weather with cold, damp and even snow in Denver for the past two weeks.  We did get two warm days stuck in the middle of each week and I took advantage to complete painting of the small parts and the engine cylinders and valve covers.

For the small parts, I used some wood clamps and some plywood on my saw horses to make a “paint fence” so I could hang the parts.

I again had some problems with paint adhering to some of the parts 🙁 , so I had to strip the turn signal brackets and repaint them.

The next warm day, I painted the cylinders and valve covers.  The valve covers have ridges that are not painted.  I thought putting a little oil on them would keep the paint form sticking.  That was not a good idea as the oil flowed down the side of the ridges requiring me to re-clean the parts.  Next, I tried axle grease very sparingly applied to the top of each ridge.  As noted below, that didn’t really work well as the paint became very sticky and was hard to remove. I primed the parts and then finished up with engine paint rated to 500 degrees temperature.  I taped off the base of the cylinder, the ends of the push rod tubes and the  top of the head where the cylinder gasket goes to prevent getting paint on these surfaces as they have close tolerances.  I also stuffed the cylinder bores with newspaper and taped off all the holes in the top of the heads.

Here’s the parts after painting.

I found that the best approach for cleaning paint off the ridges on the heads was to use a Dremel tool with a coarse sanding cylinder to remove the paint from the top of the ridge.  This also let me remove some gouges and pits in the aluminum. I masked off the covers around the ridges with masking tape to prevent mishaps.  After removing much of the paint with Dremel tool which really gummed up the sanding cylinders (I used 5 of them 🙁 ), I used a sanding block with 220 grit to get all the last bit of paint off and then finished up with 600 grit to polish the aluminum.  Here is the before and after pictures.

Finally, I baked the parts in the oven at 350 degrees for 20 mins.  I opened windows and doors to let the fumes escape. My wife, who is a saint, only mentioned that they were “stinky” as they baked …  “Nothings quite so loving as something in the oven” 🙂

I believe I have all the parts painted other than the fenders, tank, side covers and fairing which will be painted Smoke Silver.  That promises to be an adventure 🙂

I’ve been out of town more than usually over the past couple of weeks, so progress has slowed down a bit.  I discovered that the paint on the subframe didn’t adhere properly – ripples in some places and soft paint in others :-(.

I suspect the aircraft stripper wasn’t completly removed from the subframe.  I took the wire wheel and my hand drill and wire brushed the new paint off the frame.  Then, I washed it in the sink several times and finished it off with windex and paper towels to dry it.

This time I primed first and could see the primer was sticking nicely.  I did a light sand with 400 grit, washed it again and then shot it with several coats of the black gloss enamel.  When I came back from my recent travels, the enamel had no ripples and the subframe was looking great.

While I was out of town, the heads came back from Randy Long at Long’s Custom Services in Pennsylvania.  I originally sent him the head with the cracked fin to repair.  When he received it I called him to talk over the options for the repair.  Since the crack extended past the pin, I had Randy cut the pin off and fix the fin.  Upon closer inspection of the seats, Randy conclued the exhaust valve was buried too far into the head to be in spec.  I decided to ship him the other head and have him replace the exhaust valves, guides, springs and keepers.   Here’s a before, after picture set of Randy’s work.  Very nice repair.

Cylinder Fin Damage

Today, Sunday, Branden came over and we started working on putting the backend back together.  First, we cleaned the rust off the transmission input shaft and greased it with Honda Moly-60 paste.  The BMW greases don’t have a great reputation, but the Honda Moly-60 is recommended by many.  I used a toothbrush to put a light coat on the transmission splines.  It’s best to coat the transmission splines ONLY and not the clutch plate female splines.  This way, any excess grease is pushed past the clutch plates so any thrown off won’t coat the plates.  I also put a dab on the end of the clutch throw out rod to keep it and where it contacts the clutch plate from rusting.

Next, we put the transmission back in the frame and carefully inserted it into the clutch spline.  I put rags on all the freshly painted frame tubes to prevent scratching the paint job.  Here’s Branden getting it lined up.

He put the three bolts and the upper right nut back on and torqued them up.  Branden had to leave at that point, so I continued with the swing arm, rear drive and rear wheel.

I cleaned the old gasket off the rear drive and swing arm which took some time.  I found using carb cleaner and then working at the old gasket carefully with a paint scraper and brass brush finally got the 35 year old gasket off.

Next, I mounted the swing arm with the bushings and ran them in as evenly as I could.  Then, using a caliper, I loosened one bushing and tightened the opposite one until the gap was within .02 inch on each side.

Next, I torqued the bushings to the bearing preload torque and measured the gap again.  I had to loosen the bushings and readjust the gap slightly and then retorqued to the preload torque.  Then, I loosened the bushings and torqued to the final settings which are lower than the preload.  I measured the gaps again and they were within .01 inch.

Next, I mounted the rear wheel.  I found that sitting on the rear wheel when I took the transmission/drive shaft bolts off keep the shaft from spinning, so I figured it would keep the shaft from spinning when I tighted them.

I mounted the rear drive to the drive shaft.  These splines are lubricated by the gear lube in the drive shaft so you don’t need to grease them.  I rotated the drive shaft until the splines lined up, slide the rear drive on the shaft splines, and then put the nuts on the studs.  There are no torque settings so I tightend the nuts to a reasonable level.

As I don’t have the BMW tool for torquing the bolts that connect the drive shaft to the transmission output shaft, Clem suggested I use some thread lock and tighten with my 10 mm ring spanner until tight.  The bolts and washers are “use once” and get stretched when tightened, so they can’t be reused.   I put the rubber boot on that goes between the swing arm and transmission and then pulled the drive shaft up to the transmission.  Then, I put locktight on each of the new bolts and finger tighted them onto the tranmission output shaft and then leaned into them while sitting on the back tire.

Finally, I pulled the rubber boot over the swing arm and used the large ring clamp to attach it to the swing arm and used the second ring clamp to attach the other end to the transmission.  Here’s the pictures of the bike with the back end reassembled.