In preparation for removing the engine from the frame, I remove the top end (valve covers, heads, cylinders, wrist pin, cylinders) to reduce the weight. Although not part of the engine top end, I also removed and inspected the cam followers as it is convenient to do that now.
Ready To Remove Top End
This is not the first time I’ve done this. The 1983 R100RS motor is built the same as the 1983 R80ST motor, so the procedure I documented for the 1983 R100RS applies here as well. Rather than duplicate that procedure, here is the link to the documentation on the 1983 R100RS which contains all the details you need to complete this work.
This document will provide a brief summary of the procedure with pictures of what I found as I did this work on the R80ST engine along with a summary video of this work for the R80ST.
VIDEO: 1983 R80ST Remove Engine Top End and Cam Followers
And here is the longer video I made for the 1983 R100RS which contains additional information you may find helpful. However, I didn’t show removing the cam followers in this one.
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.
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.
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.
