This document shows how I disassemble a 1983 BMW R80ST “project bike” 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 November 2021 as a project bike. Consequently, a number of parts were not installed on the bike so I won’t be showing how to remove them. Nonetheless, I list the removal of parts in the order that I would have removed them so you can use this document as a guide for removing all the parts from the bike to strip it down to the frame.

After I finished disassembling it and storing parts in bins, this is what it looks like.

Record Keeping

As I disassemble a bike, I keep records of what I find. I note the condition of the parts in a project journal. An asterisk indicates part replacement, and notes indicate any reconditioning or painting that needs to be done. After I add the part to my spreadsheet parts list, I put a line through it to indicate it’s been entered into my parts spreadsheet and it’s ready to order. If I find something that I’m not sure about I use a “?” so I can go back later and resolve the question.

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 R80ST Pre-build Walk Around

Remove Gas Tank

It’s already removed.

Remove Seat

It’s already removed.

Remove Dash and Instruments

They are already removed.

Remove Headlight

It’s already removed.

Remove Electrical Wiring and Components

I show how I do that in this document.

• 61 BMW 1983 R80ST Remove Electrical System

Remove Battery & Battery Box

The battery cables were already disconnected on this project bike and the rubber straps that secure the battery in the battery box are missing. The battery box is attached with two vibration isolation studs at the top of the box and there are two more underneath the battery box where it attaches to tab on the frame.

I have to remove the battery first, but it won’t fit past the frame tubes. On other bikes I I remove the nut securing the battery box to the top vibration isolator so I can tip the battery box backward to remove the battery between the wider part of the upper frame tubes. But on the R80ST the top vibration isolator is behind the battery box so I can’t tip the box backward.

NOTE:
The rear fender has already been removed so I have plenty of clearance behind the battery. I suspect you can remove the battery without removing the rear fender.

Nonetheless, I remove the nuts securing the battery box to the top vibration isolators before removing the battery.

Then I pull the battery up and tip it backwards but it interferes with the top of the monoshock. So I have to remove the top monoshock bolt to rotate the shock to the rear to get it out of the way.

Then I find out that I can’t move the shock backward as the shackle interferes with the bottom of the right side rear sub-frame bolt.

So I remove the right sub-frame bolt so I can rotate the monoshock to the rear. The nut the bolt screws into is welded to the frame inside the pocket the top of the monoshock fits into.

I pull the monoshock to the rear to get more clearance. Now I can tip the battery backward and pull it up out of the frame.

Now I can access the nuts securing the bottom of the battery box to bottom vibration isolators and pull the box up and out of the frame.

I remove the top and bottom vibration isolators since some of them are torn and I need to remove them anyway since I’m going to powder coat the frame.

Here is the frame with the battery box and vibration isolators removed.

Remove Rear Fender Assembly

I removed this to transport the bike. The rear fender is attached to tabs on the rear sub-frame with locking nuts and a rubber washer between the fender the tab to minimize vibration and to protect the paint.

Remove Front & Rear Brakes

The front brake master cylinder, rotor and brakes lines weren’t on the bike. I remove the front brake caliper from the fork slider by removing the two large Allen bolts that secure it.

The rear brake is a drum brake so I remove the foot pedal assembly. The brake drum is part of the rear wheel and the brake shoes are part of the rear drive assembly.

I start by removing the rear brake adjusting wing nut and barrel to release the brake rod from the rear brake lever.

I remove the rear brake foot pedal bolt and lock nut to release the foot pedal from the frame. I previously removed the rear brake light switch when I removed the electrical system.

• 61 BMW 1983 R80ST Remove Electrical System
  • Remove Rear Brake Light Switch Sub-Harness And Switch

The other end of the brake rod is secured to the foot pedal with a special pivot pin that has a clip that fastens around the end of the brake rod. I can not remove the foot pedal until I remove the brake rod from the pedal.

I push the foot pedal upward so I can access the special pivot pin. I use a small blade screwdriver to push the clamp down so it rotates downward and comes off the end of the brake rod. Then I insert the blade between the leg of the pin and the brake rod bracket to wiggle it out of the hole in the brake rod and foot pedal.

Once the special pivot pin is free, the foot pedal falls out. There is a bushing in the brake foot pedal that the pivot bolt rotates inside of.

Remove Center Stand, Crash Bars And Side Stand

You can read about I do this work here:

• 46 BMW 1983 R80ST Remove Center Stand, Crash Bars and Side Stand

Remove Steering Components

All that remains to be removed is the handlebar as the handlebar controls and the combination switches were not on the bike. The handlebar is secured to the top plate with two handlebar clamps. The clamps have an upper and lower clamp. The upper clamp has studs that fit through holes in the bottom clamps and the top plate and are secured with four nuts and wave washers.

Remove Front And Rear Wheels

I remove the front wheel and the rear wheel so the bike stays balanced on the portable motorcycle lift.

The front wheel is secured with an axle. The axle is clamped in the fork sliders with two pinch bolts. I remove the axle nut and large washer. Then I remove the axle pinch bolts.

NOTE:
The blue paint on the fork sliders is not stock, but was added by a previous owner. I will remove it.

I use a large Phillips screwdriver inserted through the hole on the left side of the axle. I hold the wheel up while sliding the axle out of the fork sliders. There is a spacer on the right side that fits between the wheel and the inside of the right fork slider.

Both sides of the wheel hub are designed to hold disk brake rotors. But the R80ST only uses one disk brake rotor mounted on the right side of the front wheel hub. My rotor is missing.

The rear wheel does not have an axle. It is supported by the rear drive bearing, It mounts to the rear drive with three nuts and conical spacers. I remove the nuts and pull the wheel off the rear drive.

The right side of the hub has the rear brake drum. The left side of the wheel rim has markings identifying the size of the wheel.

Here is the bike after removing the wheels.

Remove Front Suspension

I show how I remove the front forks, top plate and the steering stem with the bottom triple clamp in this document.

• 31 BMW 1983 R80ST Remove Front Suspension

Remove Rear Drive, Monoshock and Swing Arm

I already removed the rear brake pedal and the brake rod that attaches to arm on the rear drive. You can read about how I do this work here.

• 33 1983 BMW R80ST Remove Rear Drive, Swing Arm, Monoshock

Remove Fork and Seat Locks

Unfortunately the ignition keys I got with the bike only work the ignition switch and the gas tank lock but do not work the fork and seat locks. So I got a new key made for the seat lock. But, it won’t work with the fork lock so I can’t remove the fork lock. So, that’s just the way it is.

To remove the fork lock, I remove the cover using a screwdriver and hammer to drive the cover and it’s nail out of the frame. Once the cover is removed, I would insert the key and turn it, but instead of pushing the cylinder inward to lock the fork, I would pull it out of the housing.

The seat lock is secured to a brace in the rear rear sub-frame with two bolts and locking nuts.

Remove Rear Sub-frame & Muffler

The muffler is mounted to the left side of the rear sub-frame. The muffler was the only part of the exhaust system mounted on the bike. The muffler is attached to the rear sub-frame with two bolts: one at the top and one at the bottom. The bottom bolt also secures the bottom left leg of the rear sub-frame

Here is the removed muffler. On the inside are numbers identifying it, but 18 12 1 242 931 is not the part number for the muffler. The part# is 18 12 1 242 965.

The rear sub-frame attaches to the frame with two top bolts and two bottom bolts. The right side top bolt threads into a nut welded inside the bracket the top of the rear monoshock fits into.

Here is the sub-frame after removing it from the frame.

Here is what the bike looks like at this point.

Remove Foot Pegs

The left passenger foot peg is missing. It mounts in a hole on the bottom of the muffler using the same hardware as the right foot peg. I remove the right foot peg from the frame.

The front foot pegs mount inside a bracket welded on the lower tube of the frame. The foot peg includes a spring so the foot peg can fold up if it hits an obstruction. This is similar to the R80 G/S foot peg design.

I remove the front foot pegs by removing the bolt and nut that secure it to the bracket. The bolt that secures the foot peg to the frame has a bushing the fits inside the coil of the spring. I remove the spring.

Here is the front foot peg and it’s mounting hardware.

Frame & Sub-frame Crack Inspection

At this point I inspect the welds on the frame for any cracks before I have the frame powder coated. Fortunately I found no cracks.

Remove Carburetors, Air Box & Pulse Air System

The carburetors were not on the bike. Removing them is the same as for my 1983 R100RS and I show how I do that here.

• 13 BMW 1983 R100RS Remove Carburetors & Air Box

The air box contains the pulse-air system which is in bad shape as all the rubber parts are cracked. I show how I remove the Pulse Air System and the air box here.

• 13 BMW R80ST Remove Air Box & Pulse Air System

Remove Exhaust System

Almost all of the exhaust system was not on the bike with the exception of the muffler and one header pipe hanging out of the exhaust port on the left side. The muffler is secured with two bolts to the rear sub-frame. I show how it is removed in the section about removing the rear sub-frame.

Remove Transmission

Now that the battery box and battery, rear drive, swing arm and monoshock, and the air box and interior pulse air and crankcase rebreather components are removed, I remove the transmission. You can see how I do that here.

• 23 BMW R80ST Remove Transmission

Remove Engine Top End And Cam Followers

The top end on the 1983 R80ST is the same as that on the 1983 R100RS I rebuilt. Here is a link to the R80ST work and the R100RS work.

• 11 BMW R80ST Remove Engine Top End & Cam Followers
• 11 BMW 1983 R100RS Remove Engine Top End

Remove Engine From Frame

I show how I remove the engine from the frame in this document.

• 11 BMW 1983 R80ST Remove Engine From Frame

Last But Not Least-Remove the Horn

And the last item I removed was the horn. Obviously you can remove that any time you wish. The strap the horn mounts to is important to the horn’s volume. It is made of two thin strips of steel that vibrate to amplify the sound. That said, BMW airhead horns are not very loud.

All Done

Here is the 1983 R80ST with most of the parts stored in bins.