- Work Done Prior to Assembly
- Install Engine
- Install Rear Sub-frame and Seat Lock
- Install Engine Top End
- Install Steering Stem, Front Forks, Telefix Fork Brace, Toaster Tan Top Brace
- Install Front Brakes
- Install Horns
- Install Wiring Harness and Electrical Components
- Install Transmission
- Install Clutch Throw Out Lever Assembly
- Install Swing Arm and Rear Drive
- Install Shocks, Rear Brakes and Rear Wheel
- Install Fenders, Battery Box, Tail Light, Rear Turn Signals
- Install Keihan Stainless Steel Exhaust System
- Install Rear Brake Lever, Foot Lever and Brake Rod
- Install Handlebars and Controls
- First Engine Start
- Install Seat and Cowl
- Install Fairing, Dash, Instruments and Ignition, and Windscreen
- Install Side Covers and Gas Tank
- Finished Project Pictures and Video
This write-up documents the order in which I assembled the bike from the frame through the gas cap. It includes assembly of the front forks, seat, fenders, battery box, installation of the handlebars and cables, and odds and ends that I felt were better covered here rather in an article within the parts fiche breakdown I use for cataloging the other write-ups. I include links to other write-ups where applicable to explain a particular procedure. At the end, I have some pictures and a short video of a walk around of the completed project.
I show the parts used, where applicable, in each section below. I purchased a stainless steel bolt kit from “The Bolt Guy” and used that hardware frequently, but not always.
Work Done Prior to Assembly
I stripped the bike down to the frame and powder coated it.
I created a “High Level Plan” on the “Planning The Build” page before I started and updated it as I made changes to the the plan. It lists all the work I did on the bike prior to putting it back together.
The project index page has links to the write-ups about the all the work I did on this project.
So, now it’s time to put it all back together again.
Whenever I install a stainless bolt, I put a small dab of anti-seize on the threads to prevent galling when removing the bolt. Stainless fasteners can gall and weld themselves together and anti-seize prevents that unpleasant problem.
With the engine work done, the block refinished and the powder coated frame back in hand, I install the engine block into the frame. I only install the block without the cylinders, heads, engine covers and oil filter cover as it’s easier to handle when locating it into the frame. The connecting rods were also removed since I had them refurbished.
I wrapped the frame tubes in plastic packing cloth from the powder coating company to protect it from scratches when installing the engine block and transmission.
You can not get the engine into the frame if the oil filter cover is installed.
I had my son help me get it back into the frame. The procedure I used is the same as for the R75/5 rebuild and you can read about it here.
Install Rear Sub-frame and Seat Lock
I install the powder coated rear sub-frame next. It attaches with four bolts to the main frame. I use the stainless steel bolts, washers and nuts from the kit I bought from “The Bolt Guy“.
I installed the following parts. The M8 nuts on the sub-frame have plastic vanity caps. I replaced some of the seat lock hardware due to corrosion.
|46 51 1 234 785||CAP – M82||2|
|07 11 9 907 602||FILLISTER HEAD SCREW – M3X8||1|
|07 11 9 928 562||CSK.FILLISTER HEAD SCREW – M5X40||2|
|51 25 1 230 194||PLATE (LOCK REAR PLATE)||1|
The right most bolt shown is shorter than the others so I picked the wrong one for the photo.
Here is the rear sub-frame installed.
The top sub-frame bolts mount with the heads inside the sub-frame on the 1977 R100RS instead of outside the frame as is the case for the /5 and /6 models and have counter sunk heads. The bolts supplied by “The Bolt Guy” are regular hex head. I still mount them with heads on the inside and use the black plastic caps over the nuts to complete the original look.
Here is the rear sub-frame installed.
Assemble and Install Seat Lock Mechanism
I disassembled the seat lock to clean it and remove rust. The assembly procedure is the same as for the 1973 R75/5 since the R100RS uses the same mechanism.
Install Engine Top End
The engine originally had an ALFIN cylinder and 9.5:1 pistons. But, somewhere along the line, something happened to the top end of this motor as it has the later Nikasil cylinders wi th 8.8:1 compression pistons. The higher compression pistons were not used with the Nikasil cylinders.
I learned that BMW provided 9.5:1 pistons and rings for Nikasil cylinders in Europe. I ordered those and sent them along with the cylinders to Tom Cutter at Rubber Chicken Racing garage. Since the cylinder and piston are both aluminum, the clearance is very tight (less than 0.001″ or less). Tom feels that the piston diameters vary too much an has the cylinders bored and replated to achieve a uniform, long lasting fit.
I found a score in one of the connecting rod big end bearing shells so I replace the bearings on both rods. I sent the connecting rods to be refurbished. Tom finds that they stretch and the big end to little end distance between the hole centers grows. He had them machined so the hole centers are correct and installed new small end bushings reaming them to fit the new gudgeon pins.
I also sent him the heads for new exhaust seats, valves, springs and keepers. The valve faces were thin and I did not know if the exhaust seats had ever been replaced. The original seats don’t do well with unleaded gas. After several tries, BMW came up with correctly hardened seats that don’t erode the valve faces.
You can read about how I installed the connecting rods, new connecting rod crankshaft bearings, the push rod tubes, the pistons, cylinders and heads in this write-up.
Install Steering Stem, Front Forks, Telefix Fork Brace, Toaster Tan Top Brace
With the engine block in the frame and the top end assembled, I move to the front end. I replace the stock top brace with a stronger one available from Toaster Tan.
The front fender has to be installed before the Telefix fork brace due to limited clearance between the top of the fender and the bottom of the fork brace. I included the front fender install procedure here:
You can see how I install the steering stem with new bearings, the Toaster Tan top brace, the existing Telefix fork brace, the front forks and a new steering damper in this write-up.
Install Front Brakes
I show how I install the front brakes and master cylinder after rebuilding them in the section “Install Front Brakes & Master Cylinder” of this write-up about how I rebuild the master cylinder and front brake calipers.
- 34 BMW 1977 R100RS Rebuild and Restore Front Disk Brakes & Master Cylinder
This bike came with twin Fiamm horns with a separate horn relay to increase the current flow to the horns. The horns install on a bracket that attaches to the frame. The left frame bracket was torn and I had it welded before powder coating the frame.
I installed the following parts. The M8 horn nuts have plastic vanity caps. These are the same caps used on the sub-frame nuts.
|46 51 1 234 785||CAP – M82||2|
The nuts are covered with plastic caps that are the same as the ones used on the rear sub-frame top nuts.
Install Wiring Harness and Electrical Components
I opted to refurbish the wiring harness instead of replace it. I install new electrical components including the horn and starter relays, the voltage regulator and a new Dyan III electronic ignition to replace the one I found installed. The installed ignition had damage to the rotating magnet that replaces the points and there was a lot of corrosion inside the points cover that didn’t do the point pickup sensor any good.
You can see how I install the main wire harness, various sub-harness’ and the electrical components in this write-up.
The procedure is the same as for the 1973 R75/5 project.
Note the clutch throw-out rod and it’s felt seal should be installed from the front of the transmission before the transmission is installed.
Install Clutch Throw Out Lever Assembly
I assemble the clutch throw out lever assembly and adjust the clutch cable.
I replaced most of the parts in the clutch throw-out rod assembly.
|23 13 1 232 089||ROD||1|
|23 21 1 230 440||FELTRING||1|
|23 13 1 232 088||WASHER-RACE||1|
|23 13 1 232 079||NEEDLE CAGE – 23X6X2||1|
|21 52 1 020 109||GASKET RING||1|
|21 51 1 230 109||CUP||1|
Install Later Adjustable Ball Joint Gear Shift Lever Assembly
The 1977 R100RS used the same single piece cast aluminum shift lever found on the /6 models. But this bike had the first generation adjustable gear shift lever assembly installed which I disassembled as shown here.
I ordered the new shift linkage parts as a kit from Tom Cutter at Rubber Chicken Racing Garage and got a new foot rubber (Part# 23 31 1 232 097).
I learned that this design was not very robust but the second generation with a ball joint assembly with a better design. I ordered this upgrade from Tom Cutter at Rubber Chicken Racing Garage (part # “Ball Joint/Rod Upgrade Set”).
Here are the parts of the gear shift lever assembly with the second generation ball joint assembly at the top, right.
All the other parts are the same as used with the first generation linkage and include the shift lever (under the ball joint linkage), the large Allan bolt that secures the lever to the left front foot peg, and the left front foot peg.
The diameter of the threaded pins on the second generation ball joint assembly is larger than the hole in the transmission shift arm and the shift lever that were used with the first generation assembly, so I had to drill them out a bit so the threaded pin would fit.
The large Allan bolt goes into the back side of the left front foot peg through the hole in the shift lever.
My shift lever was sloppy on the Allan bolt due to wear. I used a thin washer as a shim to reduce the gap between the shift lever and the foot peg and this reduced the wobble to almost nothing. A cheap fix. 🙂
The ball joint has two threaded pins that secure it to the transmission shift arm and the shift lever.
There is a foam rubber bushing on the pins and I push it back so I can put a wrench on the flat on the rod to tighten the self-locking nut to attach it to the transmission shift arm.
I do the same thing to attach the other end of the ball joint assembly to the shift lever.
The ball joint pushes over a ball in the linkage and is secured with a wire clip that fits into a small hole in the outside of the ball housing near the bottom. When the straight end of the wire clip is inserted, the semi-circular end is rotated around the ball housing until it snaps in place.
I adjust the foot peg to comfortable angle and torque the rear engine mount nut to 55 FT-Lbs to secure it.
The final adjustment of the lever is via the adjusting rod in the middle of the ball joint assembly. When adjusted, the shift lever should not interfere with the nut on the rear engine mount when down shifting and does not interfere with carburetor when up shifting.
Install Swing Arm and Rear Drive
I installed two new swing arm boot steel straps, four new drive shaft bolts, and a new rear drive gasket.
|33 17 2 311 098||GASKET ASBESTOS FREE||1|
|33 17 1 230 297||TENSION STRAP (to 09/78)||2|
|26 11 1 242 297||SCREW – M8X1||4|
The procedure is the same as I wrote up for the 1973 R75/5.
Install Shocks, Rear Brakes and Rear Wheel
I bought new Gazi shocks from Tom Cutter at the Rubber Chicken Racing Garage. They come with new bushings, but I had to modify the right bushing so the shock was flush against the rear drive housing. The stainless steel bolt kit from “The Bolt Guy” includes shock mount hardware.
The bottom left shock bolt is shorter than the rest and the nut is thinner than a standard nut so the rear wheel can slide past the nut.
The top shock bolts include a flat washer that goes on the outside and a wave washer and nut that go on the inside of the rear sub-frame.
The right rear shock mount is on a stud installed in the rear drive unit. However, the bushing is too wide so the shock slides on the bushing after the nut is tightened. I went to ACE and got a flat washer that would fit over the bushing pushing the shock out a bit so when the nut is tightened the shock can’t move on the bushing.
Now the rear drive is installed, I install the new brake shoes, new shocks and the rear wheel. The procedure is the same as I wrote about for the 1973 R75/5 as the rear brake assembly is the same one used on the 1977 R100RS.
Install Fenders, Battery Box, Tail Light, Rear Turn Signals
This covers installation of the front fender, rear fender, tail light and turn signal assembly and the battery box and side panels.
I got new reflectors and decals from “Heritage Stickers” for the rear fender.
|63 13 1 354 792||REFLECTOR, RED||1|
|63 14 1 244 430||REFLECTOR, YELLOW||2|
|07 11 90936 439||WASHER – 5,3||3|
|07 11 9 905 710||HEX NUT – M5 ZNS 3||3|
|R100 (/7, RS, S, CS, T, RT) warning stickers kit||Heritage Sickers
Install Front Fender
The front fender has to go on before the Telefix fork brace due to limited clearance between the top of the fender and bottom of the fork brace.
I used the stainless steel hardware from “The Bolt Guy” kit with the original rubber gaskets which were still in very good condition.
The 1977 R100RS does not use the chrome rear bracket that attaches to the bottom of the fender. It only has four carriage bolts that secure the fender to the stock sheet metal fork brace. The square stem under the bolt head fits in the square hole in the fender brace to prevent the bolt from spinning when tightening the acorn locking nut.
The rubber gasket goes on the top of the fender to protect if from scratching.
Then the flat washer and locking acorn nut go on.
Here is the front fender installed with Telefix front fork brace installed.
Install Battery Box
The battery box uses five rubber isolation damper bolts to secure it to the top of the bracket over the swing arm and to the rear down tubes of the frame. I use “The Bolt Guy” stainless nuts and washers. There is a top bracket with two plastic nuts with wave washers that secure the battery in the box.
There are three bottom rubber isolation bolts. Each end gets a nut and washer.
The top two isolation bolts install the same way.
I install the top isolation bolts but don’t add the nuts to the rear that secure it to the tabs in the frame down tubes. That way I can tip the box to the rear and slide in the Westco battery and then tip the box forward and secure it with the nuts.
Install Rear Fender
I left this off the bike until I got the rear drive and shocks mounted. The rear fender secures to two sets of tabs on the rear sub-frame. There are two metal straps that go inside the fender well and the bolt heads are against them with the rubber gasket between the top of the fender and the tab and the flat washer, wave washer and nut on top of the tab.
The fender has two holes in the front at the bottom. These fit over the metal tabs on the back of the battery box bracket on top of the swing arm.
I use “The Bolt Guy” stainless hardware and the original rubber gaskets.
This is the hardware sequence for the front fender mount; from outside the fender (left) to inside the fender (right).
The strap has a flat washer and the bolt head and mounts on the inside of the fender.
The rubber gaskets are on top top of the fender to prevent scratching it on the front fender bracket.
The bolts go through the holes in the front fender bracket with the flat washers and locking nuts attached.
The rear bracket hardware includes two rubber gaskets and two metal straps. One strap goes inside the rear fender and the other strap goes inside the rear tool box. One rubber gasket goes on top of the fender and under the rear fender bracket and the other goes on top of the fender bracket and beneath the rear tool box.
Here is the strap inside the fender and the first rubber gasket.
The rear tool box mounts on top of the rear fender bracket with the same two bolts holding the fender to the bracket.
Here is the second bracket inside the tool box.
Here is the rear fender and rear tool box mounted on the rear sub-frame.
I added a new tire pressure decal to the top of the rear fender and a factory inspection sticker.
After I installed the seat I also added the inspection sticker.
Install Tail Light and Rear Turn Signals
The tail light and rear turn signal stalk mount on a step in the back of the rear fender. This is the bracket hardware and the turn signal stem bracket.
The turn signal wires exit the tail light housing at the bottom through a rubber grommet that fits on top of the hole in the turn signal stem bracket. Each turn signal has a brown ground wire. The blue-red wire goes to the left side and the blue-black wire goes to the right side.
They thread through the turn signal stem bracket. I push them through the hole in the bracket and pull them through the end of the stems.
The tail light housing and turn signal stem bracket sit on the lip at the back of the rear fender as shown below.
The tail light housing bolts come from the bottom of the fender where the metal strap goes, through the turn signal stem bracket and inside the tail light housing where the washers and nuts go.
Assemble Turn Signals
Here are the turn signal parts.
The bracket orients the signal on the stalk so it doesn’t rotate. It mounts inside the housing with the tab fitting into a slot cut in the end of the end of the stem. I had to straight one of the tabs as it was bent and the turn signal would not stay put.
The wires inside the stem plug into terminals on the bulb housing with the brown ground wire going on the terminal that connects to the base of the bulb blue wire with red (left) or black (right) going on the terminal that connects to the center of the bulb. The housing has a cutout and goes one way.
The orange lens is marked with “TOP” so the drainage slot is at the botton of the lens when it’s mounted on the housing.
Two machine screws secure the lens bulb socket in the housing. Here is the turn signal stem bracket and turn signals installed.
Assemble Tail Light
The tail light housing includes terminals for the running light (#54)and stop light (#58) wires. Each terminal is number corresponding to the wiring diagram.
In the picture below, the green-red wire is the stop light on terminal #58 and the white-black wire is the running light on terminal #54.
The turn signal ground wires plug into the tail light assemble.
The tail light lens is secured with two screws.
Here is the installed rear fender, rear tool box, turn signals, tail light assembly, license plate bracket and reflectors.
Assemble License Plate Bracket & Rear Reflectors
Here are the parts for the license plate bracket and reflectors. I use the stainless steel hardware from “The Bolt Guy”.
There are three counter sunk screws with flat washers and locking nuts that attach the license plate bracket to the rear fender. The reflectors also use flat washers and locking nuts.
Here is the final rear fender assembly with the tail light, turn signals, license plate bracket and reflectors installed.
Install Keihan Stainless Steel Exhaust System
I replaced the headers and exhaust pipes with a new stainless steel system from Keihan. The original exhaust chrome was pitted and starting to rust.
This engine is the “CFO” version so it has the smaller 38 mm exhaust header and silencers instead of the 40 mm ones that came on the standard engine. CFO is an abbreviation for “California, Florida, Oregon” that had pollution restrictions that BMW couldn’t meet with the 40 mm exhaust system. I bought the parts from Moto-bins in the UK and the part numbers shown are theirs. In their parts description, they provide the cross referenced BMW stock part number.
If you have a standard 1977 engine with 40 mm exhaust system, the parts numbers will be different than the ones I show.
|88515||BMW 38 mm Silencers||1|
|88543||BMW 38 mm Exhaust Pipe||1|
|88741||BMW 38 mm Silencer Clamps, 41 mm||2|
|88724S||Stainless Steel Angle Brackets||2|
I install the fairing bottom side panels at the same time as the header pipes have to go through the holes in the bottom panels. You can read about how I did this here:
With the exception of installing the bottom fairing panel, the installation procedure is the same as I show for the 1973 R75/5. That said, the exhaust components look a bit different for the Keihan than the Sito system I installed on the 1973 R75/5.
Here are the Keihan system parts I purchased.
I reused the original header pipe brackets. Note they are stamped “L” and “R” for left and right bracket.
I put anti-seize on the header where it goes into the head to make it easier to remove.
Here are the rest of the photos I took while installing the Keihan system.
I loosely tighten all the hardware as I assemble the parts as this helps get everything aligned. That said, the right header spigot for the cross over pipe was not welded exactly correct so it was a bit out of alignment with the cross over pipe. It did go together but was not a simple slip fit. I have had similar “not perfect fit” parts with the other exhaust systems I have installed, so this comes with the territory.
Before I do a first engine start, I clean the exhaust system with brake cleaner to remove all traces of oil, grease and finger prints so the pipes will not stain when they are first heated.
The exhaust system is installed.
Install Rear Brake Lever, Foot Lever and Brake Rod
It is easier to install the exhaust if the brake pedal is out of the way. That’s why I install it now.
The brake rod was rusty and I decided to paint it with the same blue anodize color paint I used for the front calipers. It’s a little dash of color that you see only if you look close. This required me to remove the brake rod from the foot pedal so now I need to reassemble the rod onto the pedal.
Here are the rear brake pedal assembly parts.
The brake rod at the top attaches to the hole in the top of the arm on the brake pedal using a pin with a circular snap ring. The brake pedal attaches to the frame using the large bolt and locking nut. The bolt has a built in Zerks fitting allowing the pivot to be greased. The threaded end of the brake rod goes through a steel cylinder with a hole for the rod and is secured to the rod with a large wing nut (not shown).
Here is how I assemble the brake rod to the foot pedal with the pin
I insert the large bolt through the hole in the brake pedal, through the sleeve in the frame and secure it with the locking nut and a washer on the back side of the brake pedal.
Then I install the steel cylinder into the rear brake arm, put the rod through the hole in the steel cylinder and tighten the wing nut on the threaded end of the rod. I adjust the wing nut so the rear brake shoes touch the drum and then back it off 1/2 turn.
Install Handlebars and Controls
The fairing is very “compact” so getting the handlebars mounted to avoid contact with the inside of the fairing AND having the height comfortable AND being able to get to the levers without causing carpal tunnel problems required a number of changes.
I replace the front brake, clutch and throttle cables.
|32 73 1 235 739||BRAKE CABLE ASSEMBLY – L=619MM,D=7MM (to 09/80)||1|
|32 73 1 230 041||CLUTCH CABLE – 1345MM||1|
|32 73 1 236 616||ACCELERATOR BOWDEN CABLE – L=1108MM||1|
Handlebar Mounting Modifications
When I installed the Toaster Tan top brace and the handlebar clamps I had to modify the stock handlebar clamps by removing the threaded rod they come with and using M8 Allan bolts that screw into the clamps from the bottom of the top brace.
The stock handlebar was modified by a previous owner who drilled two holes in the left side to mount the left side plastic bracket for heated grips.. However, the holes were not drilled far enough up the bar so the end of the grip interfered with the fairing. I drilled and tapped new holes so the grip is now all the way up the handlebar. This eliminated the interference on the left side.
After I assembled the handlebars and fairing and tried adjusting the handlebar controls, I found I could not rotate them far enough down for comfort and my wrists were bent back instead of straight when I reached for the levers. In part this is due to the Toaster Tan top brace which interferes with the cable adjuster on the lever housing and also to having mounted the bars in the set of holes that move them to the rear.
I added 1 inch of height to the handlebar clamps via some four plated steel sleeves I got at my ACE Hardware (total of $12.00). That reduced the forward lean and allowed me to rotate the lever housing downward enough so when I extend my fingers to the levers, I don’t have to bend my wrists upward. It is a much more comfortable layout for me.
Install Lever Housings
These were painted rather than powder coated due to the number of threaded holes and tight clearances.
Each one has a serrated “perch” that fits in a “V” groove. The serrations grip the handlebar when the clamping Allan bolt is tightened so the housing won’t rotate.
With the perch in its “V” groove, I slide the lever housings onto the handlebars.
Installing Heated Grips
The grips each have two wires for the heating elements that thread inside the handlebar. They enter via holes next to the grips and exit at the center of the handlebar. I use a piece of wire to pull them through the handlebar ends through the center hole.
Install Front Brake Lever and Cable
Both the brake and clutch levers have a plastic bushing the pivot bolt goes through. I install new ones.
I mount the brake lever in the lever housing with the pivot bolt which is inside the throttle housing.
I install the new brake cable into the the lever using the ferrule. One side of the ferrule has a larger diameter hole than the other. The large diameter hole captures the nipple on the end of the front brake cable.
The lever housing for the front brake has a sleeve that the front brake cable fits into that looks like a cable adjuster. However, this sleeve is not threaded and you do not adjust the front brake from the handlebar, you adjust it at the master cylinder cable adjuster.
I install the other end of the front brake cable at the master cylinder cable adjuster. This adjuster has a split in it so the inner cable can slide into the ferrule. The locking nut keeps the inner cable inside the adjuster.
I screw in the adjuster all the way into the threaded hole on the left side of the master cylinder. This hole is drilled at an angle so you have to tilt the adjuster to get the threads to line up. There is another ferrule that fits on the nipple at the end of the cable just like the one used in the brake lever and I install it.
There is a pin that fits between the arm on the master cylinder and the internal piston inside the master cylinder. I put a small dab of grease on each end and position it while pulling the end of the brake cable with the ferrule installed into the cupped end of the master cylinder arm.
I will adjust the brake cable when I install the brake fluid. For now, I install the rubber boot over the master cylinder arm.
Install Throttle Cam and Cables
The throttle housing has a cam that pulls the throttle cables when the the grip is twisted. There are alignment marks on the cam and the teeth of the throttle twist grip. I insert the throttle twist grip into the lever housing so the mark on the grip aligns with the mark on the cam.
Then I install the two throttle cables into the carrier on the end of the chain.
Install Clutch Lever and Clutch Switch
The clutch lever housing has slot for the clutch switch that mounts with a small screw.
The clutch lever installs the same way as the brake lever. But the pivot pin is inside the throttle housing.
The clutch cable has a ferrule that captures the nipple on the end of the cable and fits in a hole in the clutch lever just like the brake cable. The clutch lever housing has a threaded cable adjuster. I cover adjusting the clutch lever in a later section.
Adjust Clutch Cable
I learned an easy way to adjust the clutch cable from Tom Cutter. Here is what he wrote about adjusting the cable.
“The first adjustment is made with the large threaded adjuster at the top, lever end of the cable. You need to measure the cable dimension at the LOWER end, and make the adjustment at the TOP end. The dimension should be PRECISELY 201 mm (7-15/16?) from the rear face of the transmission where the cable comes through, to the near edge of the cable barrel. You may need to turn the top adjuster out quite a ways to obtain that dimension. Squeeze the clutch lever and re-measure, as that will seat everything. The easy way to measure the 201 mm is to cut a piece of coat hanger to the exact length and use it as a gauge. Put a piece of duct tape on the middle like a flag, write “BMW Clutch Adjustment 201 mm” and you got a free BMW Special Tool.
The second adjustment is made at the rear of the transmission, using the adjuster screw and lock nut on the clutch arm. Turn the adjuster bolt in until there is NO free play on the cable, determined by lightly pulling the lever with one finger and looking at the gap at the hand lever where the cable passes through. Once you have removed all free play, back out the adjuster just enough to give 2-4 mm free play at the hand lever. To hold the adjustment while securing the lock nut, just pull and hold the clutch in with your left hand while snugging the lock nut with your right hand.”
I measure the distance from the back of the throw-out arm to the back of the boss the lower end of the clutch cable sheath sits inside of so this distance is 201 mm with my custom made coat hanger wire gauge. 🙂
First Engine Start
At this point in the assembly, it’s time to do the first engine start. There is angst in the air as now is when I learn if I made some mistake, minor or major, the prevents the engine from running. In short, “the proof is in the pudding”, and it’s time eat the pudding 🙂
I temporarily installed the gas tank and put 1 gallon in it. I set the carburetors to the basic settings for the throttle stop screw (1 turn) and the idle mixture screw (1-1/4 turn from full closed). I statically timed the Dyna III ignition. I put oil in the engine and gear lube in the transmission. I also put gear lube in the drive shaft and rear drive so all of the fluids are installed.
When I do a first engine start, I run the motor at 3500-4000 RPM for about 60 seconds. The idea is to develop enough gas pressure behind the rings push them fully into the cross hatching in the cylinders so they will seat. This initial seating ensures low oil consumption. That said, it is a bit nerve wracking to rev the motor up right away after having it dormant for the last eight months.
Here is a short video showing the bike prior to starting it and the about the first 20 seconds of the engine reving at 3500 RPM.
VIDEO: 1977 R100RS First Engine Start
It ran a bit rough. When I shut it off, I saw that one of the choke cables did not get threaded into the choke lever assembly so when I gave it choke to start, and then took it off the choke, that cylinder was running rich. I should have caught that detail, but it was easy to set it right.
Install Seat and Cowl
The seat is the original dual seat with cowl. The cowl was painted and pin stripped. You can read about how I assemble the seat and cowl, and install them here:
Install Fairing, Dash, Instruments and Ignition, and Windscreen
Installation of the fairing took some time. There are a several different fasteners, lots of each, and when installing the windscreen, not much room to get your hands where you need them.
This write-up documents how I install the fairing panels, dash, dash instruments and ignition, and the windscreen.
Install Side Covers and Gas Tank
The side covers had cracks and were repaired and painted flat black. Each side cover has two rubber bumpers, a thin one at the top and a thicker one at the bottom. Some were missing so I added some new ones and secured them with silicon seal.
I installed new roundels (part # ), some rubber spacers on the battery covers and got new battery cover decals from Heritage Stickers.
|46 63 1 233 525||RUBBER WASHER – 11MM||2|
|46 63 1 233 524||RUBBER WASHER – 4,5MM||2|
|46 63 7 686 746||BADGE – D=70MM||2|
|Battery Cover 1000cc decals||Heritage Stickers
I used masking tape to set a bottom and left edge that was the same on both covers and then stuck the decals on.
They mount with a rubber band. I drill a hole in the plastic boss the rubber band connects and safety wire them to the frame so when the rubber band fails I wont’ loose the right side cover. The left is usually stays on since the handhold keeps it captive.
The gas tank came with the 90 degree petcocks used on the later bikes. I purchased new straight petcocks and install them in the tank. Then I install new Tygon fuel lines and an inline fuel filter.
I stick on the BMW roundel on the sides of the tank and mount the tank on the bike.
The last item to go on the bike is the screw on gas cap.
Finished Project Pictures and Video
Here are some photos I took of the finished bike in the shop the night I finished in (July 21, 2017) and some I took a few days after some road tests.
Here is a video walk-around of the finished bike after I put 450 miles on it. Yes, I cleaned it up and removed the dead bugs 🙂 It will get plenty more bugs and road grime in the coming months as I built this to be a riding motorcycle, not a garage queen.
2023-04-02 Minor Edits.