The transmission on this 1983 R80ST is serial number Z 078854. According to Robert Fleischer’s article on transmissions, the range of transmission serial numbers in 1983 was from Z 074700 to Z 084299, so mine is the original transmission as it is within the range for 1983.

Transmission Serial Number Z 078854

I removed the transmission after removing the battery and battery box, the rear drive, swing arm and monoshock, and the air box and the pulse air and crankcase rebreather components.

Battery Box Removed

Rear Drive, Monoshock & Swing Arm Removed

Air Box With Pulse Air And Crankcase Rebreather Components

Air Box Removed

I found water in the transmission gear lube. The speedometer cable was missing and the hole in the bushing for the cable was plugged with some cloth. Since the bike was outside for awhile, water entered the transmission through the hole in the bushing.

Transmission Has Water In It 🙁

Here is the documentation of how I do this work along with a short YouTube video summarizing the procedure.

• 23 BMW R80ST Remove Transmission

VIDEO: 1983 R80ST Remove Transmission

I am ready to remove the engine. Before I do that I will remove the top end of the engine to reduce the weight.

Transmission Removed

The air box is secured to the top of the transmission. Inside are components for the crankcase rebreather system and for the Pulse Air System which is a passive system designed to reduce emissions to meet the US standards in the early to mid-1980’s.

Air Box With Pulse Air And Crankcase Rebreather Components-And Some Leaves

NOTE:
The picture was taken when I first saw the bike and the air box cover was missing. Leaves are not part of the crankcase rebreather or pulse air system inside the air box. 🙂

The Pulse Air System is a passive system with no active motors or moving parts. It sucks filtered air into the exhaust manifold in the heads to help burn any gasoline and to ensure CO emissions are converted to CO2. That said, according to Bob Fleischer’s information on the Pulse Air system, this increases the exhaust gas temperature and likely exacerbates wear of the valves and seats and could contribute to warped heads. The original valves and seats in 1983 had problems with valve recession due to excessive wear from the metallurgy BMW used to try and compensate for unleaded fuel.

For these reasons, I’m going to update the Pulse Air system and modify the air box so the valve train stays nice and cool. I will purchase a smog kit from Rubber Chicken Racing Garage that has all the parts needed to complete this upgrade.

Here is the documentation of how I do this work and a short YouTube video summarizing the procedure.

• 13 BMW R80ST Remove Air Box & Pulse Air System

VIDEO: 1983 BMW R80ST Remove Air Box & Pulse Air System

I’m ready to remove the transmission and the engine from the frame.

After completing this work, most of the disassembly down to the frame is complete as I also removed the rear sub-frame and muffler that is attached to it.

Rear Drive, Swing Arm & Rear Monoshock

Rear Sub-Frame Removed

Muffler Removed

Down To The Air Box, Transmission, Engine and Frame

All I have left to do is remove the air box, transmission and the engine from the frame.

You can read about how I do this work and watch a short YouTube video summarizing the work here.

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

VIDEO: 1983 BMW R80ST Remove Rear Drive, Swing Arm & Monoshock

After I removed the wheels and the handlebar, I’m ready to remove the front suspension: the front forks, the steering stem nut, top plate, steering head bearings pre-load adjuster nut and the steering stem with the attached lower triple clamp.

Bike After Wheels Removed And Ready To Remove The Front Suspension

You can read about how I do this work here:

• 31 BMW 1983 R80ST Remove Front Suspension

And here is a short YouTube video that summarizes how I do this work.

VIDEO: 1983 BMW R80ST Charity Build: Remove Front Suspension

Here’s the bike after I removed the front suspension.

Bike After Front Suspension Removed

I’m making progress on the disassembly of this project bike. That said, a lot was already removed, so this one isn’t taking me as long. 🙂

As Delivered To Brook’s Airhead Garage With Some Parts Missing

As Delivered To Brook’s Airhead Garage

The left crash bar includes a bracket for the side stand instead of mounting it on a bracket that’s part of the front engine mount stud.

Left Crash Bar With Side Stand

Side Stand Mounting Detail In Left Crash Bar

Here’s a link to the documentation of how I did this work.

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