I’ve removed the airbox, transmission, clutch and flywheel to gain access to the rear main seal so I can replace it. You can see how I did that work here.

• 13 BMW 1983 R80ST Remove Air Box & Pulse Air System
• 23 BMW 1983 R80ST Remove Transmission
• 21 BMW 1983 R80ST Remove Clutch
• 11 BMW 1983 R80ST Remove Flywheel

I’ve published documents on replacing the rear main seal on other projects. Here are links to those documents.

• 11 BMW 1983 R100RS Remove Flywheel & Rear Main Seal
• 11 BMW 1983 R100RS Install Rear Main Seal, Oil Pump Cover & O-ring
• 11 BMW 1977 R100RS Replace Rear Main Seal & Oil Pump Cover O-Ring
• 11 BMW 1975 R75/6 Replace Crankshaft Rear Oil Seal, Oil Pump Cover & O-ring
• 11 BMW 1973 R75/5 Remove & Install Flywheel, Replace Rear Main Seal, Oil Pump Cover & Cover O-Ring

Since the 1983 R80ST engine is similar in many ways to the 1983 R100RS, I link to the 1983 R100RS documents as appropriate in this document.

• 11 BMW 1983 R80ST Replace Rear Main Seal

And here is a short YouTube video showing the procedure.

VIDEO: 1983 BMW R80ST Replace Rear Main Seal

I had a real problem removing the seal on this bike using my usual approach with the Cycle Works rear main seal tool, and had to resort to using “a bigger hammer”. I used a hook seal puller to pry the old rear main seal out of the bore. Since the bike has been sitting for 25-30 years, the seal was really stuck in the bore.

Cycle Works Rear Main Seal Tool

Using Hook Seal Puller To Remove Rear Main Seal

Using Flashlight To Verify Seal Is Flush With Case