This document shows how I disassemble a 1983 BMW R100RS down to the frame. It has links to other documents that describe how to remove various assemblies such as the fairing, electrical system, brakes, etc. Although not included in this document, there are other documents that cover details about the disassembly of some of the components removed in this document; e.g., the master cylinder, disk calipers, wheel bearings, etc.

I got the bike in 2015 and did a number of things to get it running and to correct various problems like a flickering oil pressure light and the inability to start the bike unless the clutch was pulled.

• Rebuild carburetors and petcocks,
• Repair oil filter pressure relief valve
• Install new fork seals,
• Repair odometer and clock repair,
• Instrument cluster circuit board repair,
• Install new diode board with solid mounts,
• Install new alternator brushes,
• Remove Pulse-air system.

It wasn’t until 2019 that I returned to this build. I ended up acquiring a first year, 1977 R100RS and rebuilding it. That, and some other smaller projects diverted my attention. Now, I have decided to do a restoration-modification converting the bike into an R100RT with several performance and reliability improvements.

Record Keeping

As I disassemble a bike, I keep records of what I find. I note the condition of the parts in a log. An asterisk indicates part replacement, and notes indicate any reconditioning or painting that needs to be done. If I find something that I’m not sure is correct, I use a “?” so I can go back later and figure out what’s the correct part, or assembly.

On past projects I have filled in 20 or more pages of notes. These are invaluable in helping keep the project organized, fleshing out the budget with parts costs, and when assembling the bike, I often pull out these notes to refresh my memory.

I bag the parts in labeled zip lock bags. I often bag sub-assembly parts in separate bags and put them into a larger bag so it contains all the parts for the complete assembly.

This is a short video “walk around” of  the bike before I start disassembling it.

VIDEO: 1983 BMW R100RS Pre-build Walk Around

NOTE:
When I disassembled the bike, I learned the mufflers are badly rusted, so they will be replaced. 

Remove Gas Tank

The gas tank is secured by two knurled black plastic nuts under the rear of the tank and a horizontal half-round bracket with a rubber cover at the front of the tank. But, you already knew that, right? :-).

Remove Seat & Seat Cowling

Here is documentation about how I removed the seat and then removed the seat cowling from the seat.

• 52 BMW 1983 R100RS Remove Seat and Seat Cowling

Remove Battery & Battery Box

I disconnect the battery (-) and (+) cables from the battery. Then I remove the two black plastic top battery nuts that secure the hold down strap. and pull the battery up between the sub-frame rails.

NOTE:
If you can’t pull your battery out of the frame, try removing the nuts from the two top battery box vibration damper studs. Then you can tilt the battery box toward the rear fender. This will position the battery toward a wider opening in the sub-frame and you should be able to pull it up and out.

I remove the nuts from the top rubber vibration damper studs that hold the box in the frame.

The right side rubber vibration damper stud secures the rear master cylinder fluid reservoir. I use some garden wire to secure the reservoir to the frame so the brake fluid won’t leak out.df

I tilt the box to the rear and pull the battery out. Then I remove the bottom three nuts on the three rubber vibration damper studs that secure the battery box to frame and lift it out of the bike. On this bike, the middle rubber vibration damper stud is missing, likely because the rubber cracked and it broke off.

There are five rubber vibration dampers have studs on each end with nuts with wave washers on each end. The bottom studs have nuts underneath the bottom battery bracket that is welded to the frame. I remove the bottom nuts to remove the vibration dampers.

The right, top vibration damper has one longer stud. This stud secures the strap around the rear master cylinder brake fluid reservoir.

Remove Windscreen, Fairing, Dash, Volt Meter, Clock, Ignition Switch

I remove the windscreen, fairing, dash, volt meter, clock and ignition switch. Here is the documentation of how I did that.

• 46 BMW 1983 R100RS Remove Fairing, Dash, Volt Meter, Clock, Ignition Switch

Remove Headlight

I remove the headlight from the headlight shell after I disassemble the fairing. You can see how I did that here.

• Remove Headlight

The headlight shell is at one end of many of the wires in the main wiring harness. With the headlight removed, it’s easier to pull out the main wiring harness from the front of the bike as I show later.

Remove Upper, Middle and Two Lower Fairing Brackets

Now the headlight shell has been removed, I can remove the two bolts that secure the upper fairing bracket to the steering head.

A long extension on a 13 mm socket does the trick.

The bolts have a flat and wave washer.

The bracket is straight with no kinks and their is no rust or tears to any of the welds.

The headlight is still attached to the main wiring harness and I rest it on the front tire.

The middle fairing bracket is secured to the spine tube of the frame with a clam shell clamp held by an Allan bolt. The clamp is between the two cables coming out of the front of the black timing chain cover. I make note of its location because I need to get it in the same location when I assemble the fairing so the panels will mount to the ends of the bracket.

The clamp is like a clam shell with a slot on one half and a tab on the other that fits into the slot.

I pull the bracket out from the left side. The bracket has a square nut welded on the right side that the Allan bolt screws into.

There are two lower fairing brackets mounted to the front engine mount stud under the cylinders.

I remove the engine mount nuts on each side, remove the two lower fairing mounts, and then hand tighten the nuts back onto the engine mount studs. I’ll remove the studs when I’m ready tor remove the engine from the frame.

Remove Rear Fender Assembly

I remove the rear fender assembly that includes the license plate bracket with side reflectors, tail light housing, rear turn signals and stalk, the cowling tool box and the rear wiring sub-harness. You can read about how I do that here.

• 46 BMW 1983 R100RS Remove Rear Fender Assembly

Remove Electrical Wiring and Components

I remove most of the electrical components and then the main wiring harness and the various sub-harnesses that connect to it. You can see how I do this here.

• 61 BMW 1983 R100RS Remove Electrical System

Remove Front & Rear Brakes

I remove all the disk brake components (master cylinders, steel & rubber lines, and calipers). I’ll remove the disk rotors after I remove the wheels and tires. You can see how I do this here.

• 34 BMW 1983 R100RS Remove Brake System

Remove Center Stand

I remove the center stand at this point because I’m going to put the bike on my lift so it’s easier to remove the wheels and front suspension. You can leave the center stand on if you still want to use it while disassembling the bike.

The center stand on the 1983 R100RS has separate mounting tabs welded to the frame. The mounting hardware uses a countersunk Allan bolt with the head next to the oil pan and the locking nut on the outside.

There is not much clearance between the oil pan and the head of the countersunk Allan bolt. I can barely get my Allan wrench part way into the socket. If the bolt was rusted or tight, I wouldn’t have been able to remove it. What I need to do is cut down an Allan wrench to fit and add that to my special tools stash.

The head of the countersunk bolt interferes with the lip of the oil pan. I learned that the trick to getting it out is to remove the center stand springs and then the pivot bolt bushing. This will free up the pivot bolt in the hole so I can tilt it downward and slide it past the oil pan.

The bushings have grooves worn into them. I’ll replace the countersunk head bolts, lock nuts, bushings and the springs as these are all high stress and wear items, so now is the time to refresh them.

The center stand legs are worn through. I’ll have patches welded onto them.

Remove “Repair Kit” Side Stand

The stock side stand has been replaced with a repair kit (part# 46 53 1 454 750).

The side stand has failed. But, there is also a Brown’s side stand on this bike which is very convenient as it is not obscured by the fairing so it’s easy to see if it is retracted and to get to with you foot. I removed the damaged side stand repair kit to get it out of the way. I won’t replace it with another repair kit. I’ll remove the Brown’s side stand when I get the engine out of the frame.

That said, here are some pictures showing how the the repair kit components are mounted and showing the damage. I suspect someone sat on the bike with the side stand down and bent the arm of the side stand yoke making it loose and floppy.

I remove the shackle with the two springs. That lets me remove the pivot bolt, the brass bushing, and the side stand.

Remove Steering Components

I remove the steering components which include the handlebar controls, the handlebars, the instrument cluster, the instrument cluster bracket, and the steering damper assembly. You can see how I do this here.

• 32 BMW 1983 R100RS Remove Steering Components

Remove Front Suspension Components

I remove the front suspension components which include the front wheel, the front fender, fork brace, fork lower sliders, fork tubes, steering stem and fork top plate. You can see how I do this here.

• 31 BMW 1983 R100RS Remove Front Suspension Components

Remove Rear Wheel, Rear Drive, Shocks and Swing Arm

With the rear fender assembly removed, I can remove the rear wheel, rear drive, rear shocks and the swing arm. Since I use the rear wheel to immobilize the drive shaft when removing the four bolts that secure it to the transmission output coupling, I leave the rear wheel on while I remove the four drive shaft coupling bolts. Then I remove only the right rear shock which is mounted to the rear drive using the left one to keep the swing arm level. After I remove the rear drive from the swing arm, I remove the left shock and then the swing arm. You can see how I do this here.

• 33 BMW 1983 R100RS Remove Rear Wheel, Rear Drive, Shocks & Swing Arm

Remove Rear Sub-frame

With the swing arm removed, I can remove the rear sub-frame. The left-side grab handle for helping put the bike on the center stand is attached with the top left sub-frame bolt. There is a black plastic vanity cover over the nut and it’s the same as the vanity cap used on the horn bolt head. The bolt is a countersunk Allan style and has the head on the inside of the sub-frame. This provides more clearance when removing the battery. I remove the vanity cap and the bolt.

The other bolt at the bottom leg of the sub-frame goes through the muffler bracket on the frame. I remove it.

The right side of the sub-frame is mounted with the same hardware as the left and I remove it. Then I can slide the sub-frame to to the rear to remove it.

The other end of the grab handle is mounted with a bolt into the seat lock mechanism. I’ll remove it when I remove the seat lock.

Frame & Sub-frame Crack Inspection

With the sub-frame off, I can inspect the welds and the sub-frame for cracks. Often, the sub-frame welds crack or the tubes break. Also, the welds on the gussets at the rear of the frame can crack. It’s easy to repair these now if any welds are broken. All these welds are not cracked.

The side covers are held in place with steel tabs welded to the support arms of the sub-frame. The tabs on the right side of the sub-frame are broken, so I will have to fabricate new ones and get them welded onto the support arm.

The seat hinge pins on the right top rail of the sub-frame can be cracked. Mine are rusty, but the welds are okay.

The pins for the tire pump can also get broken. Mine are okay.

The sub-frame cross-rail gusset welds can crack, but these are okay.

The rear frame lower cross-brace tube has a gusset that attaches to the muffler bracket and these can crack. Mine are rusty, but otherwise okay. The frame rear down tubes weld to the swing arm bushing and rear muffler bracket. These welds are okay.

The rear brake switch bracket is welded to the inside of the right muffler bracket and it has no problems.

So far, the sub-frame and welds on the rear of the main frame are in good condition with no broken welds. These are one indication that supports the notion this bike has not been crashed as that often causes welds to tear and tweak the frame.

Here is what the bike looks like now.

Remove Carburetors & Air Box

These are straight forward to remove. I show how to do that here:

• 13 BMW 1983 R100RS Remove Carburetors & Air Box

Remove Exhaust System

This bike has a Brown side stand. Installation of this side stand slightly changes where the left side header pipe bracket is mounted. Normally the bracket is mounted on the rear engine mount stud. With the Brown side stand, it is mounted on the front of the Brown side stand bracket. Here is how I remove the exhaust system.

• 18 BMW 1983 R100RS Remove Exhaust System

Remove Transmission

To remove the transmission, I first remove the clutch throw-out lever and the foot shift mechanism. Then I remove the transmission and the clutch throw-out rod. You can read about how to do this here.

• 23 BMW 1983 R100RS Remove Transmission

Remove Engine Top End

To make it easier to remove the engine from the frame, I remove the top end. You can see how I do that here.

• 11 BMW 1983 R100RS Remove Engine Top End

I shot a short video showing the procedure which is quite straight forward.

VIDEO: 1983 BMW R100RS Remove Engine Top End

Remove Engine From Frame

I am now ready to remove the engine from the frame. I need to remove the oil filter housing which I left connected when I removed the oil cooler as part of the fairing removal. Then I remove the front and rear engine mount studs.

Remove Oil Filter Cover

I remove the three Allan bolts that secure the cover.

Under the oil filter cover is a large, white o-ring and two metal shims. In the cover is a black, square profile o-ring.

WARNING:
See below for more details on the shims. The number of shims I show is specific to this engine and the depth of it’s oil filter canister. You may need a different number of shims.

The shims are critical to sealing the oil filter housing so oil is delivered within the engine. You can read more about how to decide how many shims to use here.

• Checking Oil Filter Canister Depth and White O-Ring
• Oak Okelshen Formula for White O-ring Compression

I pull out the oil filter and then check the oil filter pressure relief valve to be sure the screw is seated and the slot in the screw aligns with the slots in the oil filter housing.

Remove Engine Mount Studs

I removed the foot pegs earlier. I have the engine sitting on a piece of wood on top of my motorcycle lift. When I remove the engine mounting studs, the frame will try to drop down, but the engine will be secure on the lift.

I remove the rear engine mount stud. There are two spacers between the engine and the frame and a large spacer in the middle. I leave the middle spacer in place. The stud slides out easily with just a couple taps on a drift with a hammer to loosen it.

I remove the nuts and washers securing the front stud and slide it out using a wrench on side and a socket on the other. At this point, the frame drops down onto the board under the oil pan.

There are two spacers between the frame and engine block that the front engine stud slides through. These are the same dimensions as the ones used on the rear engine mount stud. And, the two studs are the same length, 12 -1/16 inches (306 mm).

Remove Engine

I find the engine wants to tilt forward when not connected to the frame, so I secure it with a strap around the rear of the engine, but not the frame, and under the arms of the portable motorcycle lift to stabilize it. Then I shift the frame forward so the engine is up against the rear cross-brace of the frame.

NOTE:
In this description, “left” and “right” refer to the sides of the bike when you are riding it, which is the rule, not to the side of the bike seen in the photos when facing the front of the bike.

Then I tilt the frame to the left so the spine tube is on the left side of the top engine cover and there is a clear path upward for the engine.

In this orientation, I can bend down on the right side of the frame, remove the strap while balancing the engine. Then I use my legs to pick up the engine. As I lift it, I tilt the engine to the right and lift it out of the frame. Then I put it down on the floor. I estimate it weights about 50 Lbs with the top end removed.

Then I strap the engine to the portable lift for now.

At this point, the bike is disassembled. Here is most of it except for the fairing and fenders that are at the painter.

Remove Fork and Seat Locks

I remove the fork lock from the frame and the seat lock mechanism from the sub-frame. I need to remove them before having them powder coated. You can read how I do that here.

• 51 BMW 1983 R100RS Remove Fork & Seat Locks

Revisions

2019-11-17  Edits and typos.
2020-02-20  Clean up Brown’s side stand.