- Project Index and Videos
- Assemble The Engine Block
- Install The Engine Block In The Frame
- Install Push Rod Tubes and Cylinder Studs In Cylinders
- Install Connecting Rods and Cam Followers
- Install The Engine Top End
- Install Drive Shaft and Swing Arm Bearings
- Replace Steering Head Bearings
- Install Steering Limit Bolt In Steering Head
- Replace Main Wiring Harness
- Lengthen Right Handlebar Switch Wires
- Replace Ignition System with EME Optical Electronic Ignition System
- Remove, Refinish & Install Brake Rotors
- Replace Wheel Bearings And Adjust Preload
- Rebuild Forks with Race Tech Cartridge Emulators
- Install Toaster Tan Fork Top Brace And Install & Align Front Forks
- Install Swing Arm and Rear Drive
- Install Sub-Frame
- Install Fork and Seat Locks
- Install New Gazi Rear Shocks
- Install Wheels
- Install Fairing Brackets
- Install The Headlight Shell
- Routing The Main Wiring Harness
- Install Electrical System
- Rebuild Transmission
- Install Transmission
- Install Handlebar Perches And Switches
- Shim Oil Filter Canister, Install Oil Cooler & Filter
- Install Rear Brake System
- Install Front Brake System
- Install Steering Damper Mechanism.
- Install Exhaust System
- Install Center And Side Stands
- Install Carburetors, Cables And Air Box
- Assemble And Install Gas Tank
- First Engine Start
- Assemble And Install Fairing & Windscreen
- Front Fender
- Assemble And Install Seat Cowl & Seat
- Install Side Covers
- Project Complete
- Reupholster Seat And Add Back Rest
- Add Electrical Accessories and Farkles
This document shows how I assemble this bike starting from the frame. I show the order of assembly and frequently link to other documents that provide all the details. For shorter and less complicated parts of the assembly, I’ll document what I do in this document.
On this project, I’m converting a RS to a RT configuration. That involves mostly changes to the fairing, handlebars and controls.
I started with this.
And, it mostly fit into these bins (with the exception of the fairing pieces and gas tank) after I completely disassembled it.
Project Index and Videos
I organized all the work by subsystem in the Project Index document.
I made a number of videos to supplement the project documents and posted them on my YouTube channel.
Assemble The Engine Block
On this project, I stripped the engine down to the block. Due to an issue with a low oil pressure light right after I got the bike, I wanted to verify the condition of the main bearings. Here is the order in which I assembled the engine block before I installed the engine block in the frame.
- 11 BMW 1983 R100RS Install Crankshaft, Adjust End Float, Install Camshaft
- 11 1983 BMW R100RS Install Rear Main Seal, Oil Pump Cover O-ring & Flywheel
- 11 BMW 1983 R100RS Install The Flywheel
- 21 BMW 1983 R100RS Install Clutch
- 11 BMW 1983 R100RS Install Crankshaft Sprocket, Nose Bearing, Timing Chain, Front Main Seal, Inner Timing Cover
- 11 BMW 1983 R100RS Replace Oil Pan & Oil Pump Suction Flange Gaskets, Get Oil Pan Mating Surface Flat
Install The Engine Block In The Frame
I always think of this as the start of creating order out of the chaos of a completely disassembled bike.
Install Push Rod Tubes and Cylinder Studs In Cylinders
I did this work on the bench in preparation for installing the top end.
Install Connecting Rods and Cam Followers
I did this work on the engine block after I installed the engine in the frame
Install The Engine Top End
I like to do this after the engine is in the frame because the engine block is much lighter without the top end installed.
Install Drive Shaft and Swing Arm Bearings
I removed the drive shaft and swing arm bearings since I had the swing arm powder coated.
Replace Steering Head Bearings
I removed the steering head bearings before I had the frame powder coated. Then I installed new bearings.
At this point I could install the steering damper mechanism, but I prefer to wait on that so there is more room to work when I install the main wiring harness, the handlebar cables and wiring, and the front brakes.
Install Steering Limit Bolt In Steering Head
The RS and RT fairings are so close fitting that the handlebar movement has to be restricted to keep the ends of the handlebars from contacting the inside of the fairing. I install the bolt and lock nut in the hole in the front of the steering head.
If you use too long a bolt, you will not be able to move the handlebars far enough to push the fork lock tumbler all the way into it’s slot. The stock bolt is an M6 x 22 mm and is part# 07 11 9 904 505.
Replace Main Wiring Harness
I decided to install a new main wiring harness. One end of the main harness terminates inside the headlight shell. I removed the old harness connections and then installed the new harness connections inside the headlight shell.
Lengthen Right Handlebar Switch Wires
The RT handlebars are longer than the RS so the handlebar switch wires are longer for the RT. The left handlebar switch had been replaced previously with one that has the longer RT wires, but I had to lengthen the wires on the right switch.
Replace Ignition System with EME Optical Electronic Ignition System
This bike has the bean can with electronic trigger (Hall effect sensors) and electronic ignition control unit. I decided to replace them with a crankshaft mounted optical trigger with multiple advance curves and electronic ignition control unit from Euro MotoElectrics. I did this work with engine in the frame.
Remove, Refinish & Install Brake Rotors
I had the wheels powder coated so I removed the brake rotors. When I got the wheels back I refinished the rotors and installed them on the wheels.
Replace Wheel Bearings And Adjust Preload
I removed the wheel bearings before having the wheels powder coated. I installed new bearings and adjusted the bearing preload.
Rebuild Forks with Race Tech Cartridge Emulators
I upgraded the forks while rebuilding them by installing cartridge emulators from Race Tech. They should provide better compliance than the damper rods BMW uses.
Install Toaster Tan Fork Top Brace And Install & Align Front Forks
I replaced the thin, flimsy BMW fork top plate with a Toaster Tan fork top brace which is much beefier. This makes the front forks more rigid and improves handling. Installing the fork top brace is part of the process of installing and aligning the front forks. Aligning the forks makes a large difference in compliance as it greatly reduces friction between the fork tubes and the fork lower sliders, aka fork “stiction”.
- 31 BMW 1983 R100RS/RT Install Toaster Tan Top Fork Brace
- 31 BMW 1983 R100RS/RT Install and Align Front Forks
Install Swing Arm and Rear Drive
The rear drive on this year bike has the 12-sided nuts that secure it to the right side swing arm flange.
The sub-frame attaches at four points to the frame. This year bike uses recessed Allen bolts at the top so it’s easier to install and remove the battery.
The lower sub-frame legs mount to holes in the rear foot peg & muffler brackets on the frame.
The grab rail is secured by the front, left sub-frame bolt and an Allen bolt that threads into a hole in the rear of the grab rail from the inside of the sub-frame.
All the bolts are torqued to 18 FT-Lbs. The top nuts have a black plastic vanity cover the fit over them.
Install Fork and Seat Locks
I replace the special “nail” that secures the fork lock cover as it gets damaged when I remove them.
Install New Gazi Rear Shocks
I install new Gazi rear shocks that I ordered from Tom Cutter at Rubber Chicken Racing Garage.They come with some hardware and hook spanners for changing the rear spring preload to adjust the rear suspension sag. The also have adjustable rebound damping.
The top of the shocks include two large diameter, thin flat washers and a bushing and the bottom of the shock includes a thicker flat washer which is used only on the right rear where the bottom of the shock is secured by the stud in the top of the rear drive.
The top shock mounting hardware includes the bolt, a flat washer that fits under the bolt head and a wave washer and nut the fit inside the sub-frame.
The top of the shocks use the same hardware.
But the bottom of the shocks use different hardware on each side. The left side bottom hardware includes a shorter bolt, a flat washer that goes under the bolt head and a thin nut that mounts inside the frame. This allows the rear wheel to clear the lower shock mount when removing it.
The right rear shock mounting hardware includes a large flat washer that fits against the side of the rear drive, the thicker flat washer that came with the Gazi shock, a wave washer and a nut.
I install the right shock starting at the bottom by sliding the large flat washer and then the lower shock bushing over the rear drive stud.
Then I rotate the shock forward to slide it into the clevis channel at the top of the sub-frame while sliding the two Gazi thin flat washers on either side of the top shock bushing.
My clevis channel welded to the top of the sub-frame was bent enough that I couldn’t install the Gazi thin flat washers. I used a shop rag to wrap my channel lock pliers with and used them to bend the inside of the clevis bracket until the bushing and thin flat washers would fit. I found rotating the shock all the way to the front, slipping the Gazi thin flat washers against the shock bushing and then rotating the shock backward to align it with the center hole worked well.
The right shock top bolt mounts in the center of the three holes in the clevis bracket.
I torque all four shock bolts to 25 FT-Lbs.
I’ll adjust the rear shock sag later when I have finished the project.
I had the wheels powder coated in white. This color was used on the R65LS bikes and I like the contrast with the tires. I think I lightens the look of the bike.
I start with the rear wheel. I apply a thin coat of wheel bearing grease to the axle. Next, I apply some Moly-60 to the splines of the rear drive unit. These splines engage the splines in the rear wheel.
Then I install the rear disk brake plate on the left side of the rear wheel with the casting numbers facing outward. I slide the rear axle through the frame and the hole in the disk brake plate, through the wheel and secure the axle with the large chrome flat washer and nut. I torque the rear nut to 25 FT-Lbs which is the torque I used when I set the wheel bearing preload.
Over torquing the rear or front axle nuts can cause the wheel bearings to over heat and freeze up. If that happens, you will not have a nice day and will likely add some EMT folks to your list of new acquaintances. :-(.
The front axle hardware includes a spacer that fits on the right side of the axle. Like I did with the rear axle, I put a light smear of wheel bearing grease on the axle.
I check the new front tire for the arrow showing the direction of rotation so I install the wheel with the correct side on the left.
I push the axle in from the right side, slide the spacer between the wheel bearing and left fork slower slider and slide the axle all the way through. I install the washer and nut and torque to 25 FT-Lbs.
Here’s the bike with it’s new shoes on. It’s starting to look like a motorcycle again 🙂
Install Fairing Brackets
I install the top, middle and bottom fairing brackets. The top bracket attaches to the steering head with two bolts that screw into tapped holes in the front of the steering head. The bolts have a flat a wave washer.
The middle bracket fits on the lower tube that reinforces the steering head. The cross piece mounts so that the square nut is on the right side and the Allen head bolt, flat washer and wave washer are on the left side. The cross piece is approximately centered between the two cables exiting the inner timing and top engine covers. The cross piece is angled and the ends point to the front as shown below.
The bottom brackets mount on the front engine studs. The brackets are “handed” with the nose pointing to the front. The leg of each bracket is above the engine stud as shown below.
Install The Headlight Shell
After I install the top fairing bracket on the steering head, I install the headlight shell between the ears of the top fairing bracket.
I start on the left side. I install a flat washer and the rubber gasket on the cylindrical plug in the headlight shell. Then I insert the plug into the hole in the left ear. Then I add the second rubber gasket, the flat washer, the wave washer and the chrome nut.
There are two rubber gaskets, a large flat chrome washer and a chrome headed nut on the right side. The right side of the headlight shell slides pass the right bracket ear. Then I insert one of the rubber gaskets between the headlight shell and the ear. I install the other rubber gasket, flat washer and chrome headed bolt.
Here is the headlight shell installed in the top fairing bracket.
Routing The Main Wiring Harness
This shows how I route the main wiring harness and what goes where.
Install Electrical System
This document collects links to other documents and contains new information. It’s an index to all the details for installation of the complete electrical system.
The air box can not be installed if the battery box is installed as the air box has to slide to the rear to fit over the top, right transmission mounting stud. You may want to install the air box before you install the battery box and battery.
I could have done this work at any time after I removed the transmission. But at this point in the project, I felt like I was in the right frame of mind to focus on this bit of precision work. This is the second transmission I have rebuilt, so I am not an expert by any means. I wrote five documents showing how I do the work. Each has a link to an accompanying video summary.
- 23 BMW 1983 R100RS Disassemble Transmission
- 23 BMW 1983 R100RS Rebuild Transmission Shift Cam Assembly
- 23 BMW 1983 R100RS Rebuild Transmission Input & Intermediate Shafts
- 23 BMW 1983 R100RS Rebuild Transmission Output Shaft
- 23 BMW 1983 R100RS Assemble Transmission
I installed the transmission in the frame, mounted it to the engine block, connected it to the drive shaft, assembled the clutch throw-out mechanism, attached the speedometer cable, the neutral switch wiring and the foot shift. This shows how I do that work.
Install Handlebar Perches And Switches
This shows how I did this work. I’ll connect the lower throttle and choke cables when I install the carburetors.
Shim Oil Filter Canister, Install Oil Cooler & Filter
It is critical to shim the oil filter canister correctly so the white o-ring that goes on top is compressed enough to seal the canister and the oil filter cover. It this seal fails, the engine gets no oil.
I also show installation of the oil cooler and filter.
Install Rear Brake System
This shows how I install the rear brake lines, master cylinder, master cylinder bracket, fluid reservoir, rear brake caliper and rear brake stay.
You have to remove the battery box to install the steel brake line from the rear master cylinder on the right side of the swing arm that goes to a bracket on the left side of the swing arm that holds the brake hose from the rear caliper that the steel brake line screws into.
Install Front Brake System
This shows how I install the front brake system steel lines, rubber hoses, calipers and bleed the system. I also show a modification to the front brake line manifold under the gas tank. I remove the front brake pressure switch and plug the hole. I’m using the right handlebar perch mechanical front brake switch instead.
Install Steering Damper Mechanism.
I could have installed this after I installed the steering stem, but held off so there would be more room to work on the wiring, handlebar cables and front brakes.
Install Exhaust System
I installed a new exhaust system from Euro MotoElectrics as the original system was pretty rusty.
Install Center And Side Stands
I am not using the stock side stand for three reasons: the bushing and bolt are trash, it’s in an inconvenient location hidden by the cylinder and lower fairing panel when extended making it hard to deploy, and the bike came with a Brown’s side stand which mounts further back on the frame so it’s easy to deploy. I repaired and powder coated the center stand and replaced the pivot bolts and bushings due to wear and tear.
Install Carburetors, Cables And Air Box
I change the jets in the carburetor since I increased compression from 8.2:1 to 9.5:1 and installed dual plug heads.
Assemble And Install Gas Tank
I removed all the fittings from the gas tank prior to having it repainted.
I install the petcocks with the in-tank filter screen and the gasket on top of the shoulder on the bottom of the screen. Then I tighten the special nut onto both the petcock and the tank nipple. The side of the nut that screws onto the petcock is a reverse thread while the end the attaches to the gas tank nipple is a regular thread. When the nut is tightened, it tightens onto both the petcock and the gas tank nipple.
On the bottom of the gas tank is a nipple for the overflow hose. I attach it to the bottom of the tank and route it along the bottom right side of the tank being sure it isn’t kinked.
The tank fits on a rubber bumper at the front and on two vibration isolation studs at the rear. The rear isolation studs are attached using nuts and wave washers.
I route the fuel overflow hose along the rear frame tube and route the hose behind the rear brake master cylinder clamp so it exits near the rear foot peg underneath the frame.
After mounting the tank, I attach the new roundels on the sides so they are straight.
After I mounted the carburetors, I install new Tygon fuel line. I start by installing the cross-over line through the holes under the front of the air box and connecting each end to a tee. Then I install hose on the carburetor and cut it length so it fits on the bottom of the tee. Then I cut the line that goes from the petcock to the top of the tee. Before I install the hose on the petcock nipple, I slide on a nylon washer on the petcock nipple. I can grab it and wiggle the hose off the tee easily.
First Engine Start
A major milestone is the first engine start. I usually perform this earlier in the build than I am on this project. But, my gas tank and the other parts that I had painted have been delayed coming back, so I’ve done everything else I can do until I got the gas tank in hand.
Assemble And Install Fairing & Windscreen
I’m converting the original RS fairing to an RT. I had the fairing, front fender, side covers and gas tank painted in a two tone paint scheme, code 130, used on the RS bikes; the colors are Dunkel Blue and Hell Silver. The RT fairing includes side storage boxes that attach to the inside of the upper side panels, but I do not plan to use them as they fit too close to the gas tank for my comfort.
I had a professional pinstriper apply the pinstripes.
I left the front fender off until I finished installing the fairing to protect the new paint should I drop a tool or part on it.
The fender attaches to the fork brace using four carriage bolts, a rubber washer that fits on top of the fender, a large flat washer and an Acorn nut. I tighten the Acorn nut enough to expand the rubber washer until it’s almost as wide as the flat washer on top of it.
Here is a short video.
Video: 1983 BWM R100RS Install Front Fender
Assemble And Install Seat Cowl & Seat
This shows how I assemble the seat cowl, attach the seat to it and install the seat on the hinge pins on the rear sub-frame.
Install Side Covers
The covers were painted Hell (Bright) Silver with matte clear coat, but the original paint scheme uses gloss clear coat. The side covers get a decal that I got from Heritage Stickers. The one used with this paint scheme has an outline of the numbers and letters rather than a filled in character. The decal has a paper backing that covers the adhesive and a clear film that lightly adheres to the front of the characters. I start out by cleaning the surface of the side cover the decal sticks to with an alcohol wipe to so there’s no oil or finger prints on it.
I have to be careful when removing the decal from the paper backing so I don’t disturb the characters. The paper backing does not want to separate from the decal easily. I find that keeping a sharp crease at the edge of the paper helps the decal come loose without disturbing it or pulling it off the clear film on the front of the decal.
I carefully handle the decal so I don’t touch the adhesive on the back of the characters. To align it on the side cover, I put the paper backing under the sticky side of the decal to get it oriented and centered and then pull the paper out and smooth the characters with my fingers to get them to adhere. Then I use a pencil eraser to burnish the outline of the characters to make sure they adhere to the side cover before I peel the clear film off the front of the characters. I keep a sharp edge on the clear film so the characters do not lift off the side cover.
Finally, I burnish the outline of the characters again with the pencil eraser to make sure they fully adhere to the side cover.
I add the two different thickness rubber bumpers to the inside of the covers. The bumpers butt up against the sub-frame tube and keep the side covers from rattling. The top bumper is the thin one (part# 46 63 1 233 524) and the bottom one is the the thick one (part # 46 63 1 233 525). I attach them with Silicone Seal.
I attached the two side covers with the elastic cord (part# 07 11 9 905 680). To mount the left one, I remove the bolt securing the front of the grab handle and loosen the rear one so I can rotate it upward so the notch in the left side cover can fit around the handle. After I install both covers and secure them with the elastic I bend the metal tabs into the slots to keep the side covers from falling off if the elastic cord breaks.
I restarted the project on March 1, 2019 after acquiring this bike in January 2015. My 1977 R100RS rebuild project halted work on this bike as I wanted to complete the 1977 RS in time to attend the 40th anniversary rally hosted by Todd Trumbore. I finished assembling this bike on September 30, 2020, so the build took about 18 months to complete. The link below includes before/after pictures and video walk-arounds, some pictures of details and a list of those whose help made this project possible.
Reupholster Seat And Add Back Rest
The seat had a tear and I had it reupholstered and custom fitted so it would be comfortable on long rides for me and my wife. I also replaced the grab rail with another one from Reynolds that included a back rest and a rack. However, the back rest was missing so I had Bitchn Stitchn make one. Here is a write-up about how they did that work.
Add Electrical Accessories and Farkles
After I rode the bike for about 600 miles, I added several electrical accessories including:
- Auxiliary Fuse Box
- Heated Grips With 1988+ High-Off-Low Switch
- Auxiliary LED Driving Lights
- Garmin GPS Power Cradle
- Auxiliary USB and SAE Sockets
2020-06-16 Add fairing brackets and headlight shell install.
2020-06-17 Add Routing the Main Wiring Harness.
2020-07-10 Add Rebuild Transmission section.
2020-07-22 Add Install Transmission and Install Handlebar Perches sections.
2020-08-01 Add Shim Oil Filter Canister Section & Install Electrical System.
2020-08-08 Add Install Rear Brake System.
2020-08-12 Add Install Front Brake System.
2020-08-17 Add Install Steering Damper Mechanism.
2020-08-19 Add Install Exhaust System.
2020-08-22 Add Install Center And Side Stands
2020-08-25 Add Install Carburetors, Cables And Air Box & a note about installing air box before battery box and battery.
2020-09-08 Add First Engine Start.
2020-09-12 Add Assemble And Install Gas Tank.
2020-10-04 Add Assemble And Install Fairing & Windscreen.
2020-10-06 Add Install Front Fender and Assemble And Install Seat Cowl & Seat.
2020-10-08 Add Pinstriping.
2020-10-11 Add Install Side Covers and Project Complete.
2020-10-18 Add detail to Install Side Covers section.
2020-11-27 Add Reupholster Seat And Add Back Rest section.
2020-12-12 Add Install Electrical Accessories & Farkles
Brook, I would interested in your comments pertaining to how the rear shocks perform in comparison with some of the other shocks, other than standard equipment, that you have installed in the past.
I have used Gazi shocks on two other bikes: 1975 R75/6 and 1977 R100RS. I like them.
I have a 1981 BMWs R100Rt that I being assembling by part but I have being with this problem trying to assembling my rear wheel. my rear axle can’t go all through it’s get stocked by the brake holder. have tried many different thing to get it done.
I wish that you could make a video or help me with my situatuion.
thanks for your time.
It’s possible the tube that sits inside the wheel and that holds the bearing pre-load adjustment wedding bands has shifted and is obstructing the axle. You say you think it’s the “brake holder” on the left that is the problem.
Can you push the axle through the wheel if you remove the brake holder plate? If so, look at the plate to see if it is damaged in a way that the hole obstructs the axle.
I hope that helps.
I have a question regarding engine mounting which I think your expertise would speak to, and have the right answers to.
Airheads seem so A-symetrical, I am unsure how the engine should mount in the frame. I am rebuilding an R60/7 where I have placed the same size spacers (and stand spring mounting hardware) on either side of the engine on the mounting studs in the frame. When regarding the engine from the rear and front it seems the engine is off to one side, LHS. is this to counter the weight of the swing arm/drive and alike, or have I spaced incorrectly? I believe this lack of centring may affect the header mounting and other elements.
Any advice would be very much appreciated! And thank you for all the truly enlightening articles and instructional to date!!
As long as you installed the two shackles on the front engine stud between the engine and the frame and the two spacers on the rear stud between the engine and the frame, then the engine is installed correctly in the frame.
The drive shaft alignment with the transmission output flange may require the engine to be off center, but I can’t say I ever checked that to know if that’s true.
As I show in the document on installing the swing arm, 33 BMW 1983 R100RS Install Swing Arm and Rear Drive getting the swing arm centered in the frame is important to reduce wear on the drive shaft.
I hope that helps.