To gasket, or not to gasket? Final drive and swingarm 198R80ST

[sidkn33]

In general, there are variations on this theme - when is a gasket required and when one is not?
My R80ST is having an upgrade to the rear brake cam bushes to prevent oil leaks into the rear brake (the final drive is soon to arrive with @mikeyboy via Overland and Classic) - this obviously meant removing the final drive and mine has no evidence of a gasket between it and the swingarm.
In this youtube video, detailing the installation of the swingarm, final drive and shock (one of many by the esteemed Brook and Branden's Airhead Garage on a complete ST tear down and rebuild). at 11:16 Brook states that the R80ST did not have a gasket between the swingarm and final drive.
However, he then immediately says to use a Permatex anaerobic gasket maker product and associated Permatex surface prep aerosol - the latter is not available anywhere I can find in the UK - then proceeds to use that gasket goo between said swingarm and final drive.

Why would the ST (and presumably the G/S) not require a gasket from the factory (vs other monolevers and Airheads in general) and then why would someone who clearly knows more than the average Airheader, recommend a specific anaerobic gasket product when refitting the final drive if there was no gasket to begin with?
And why not a standard gasket vs some weird anaerobic stuff?

 

[NeilDD]

Permatex is available on eBay
Use isopropanol to wipe the surfaces clean, allow to dry.
Place a bead of the RTV sealant, wait 5 min's then re assemble

Anaerobic just means goes off when no air is present

 

[sidkn33]

Thanks, yes I found the Permatex anaerobic stuff on eBay,
Any idea why I'd be putting a gasket in place when none is evident from the factory?

 

[Gelandestrasse]

No gasket required. If you did you'd likely get a leak. I've used RTV or Hylomar before; both work well.

Later models (K-series, 1100, 1150, 1200 etc) use goo instead of gaskets because the machining tolerances are much better. Or big rubber bands.

 

[sidkn33]

I guess I'll goo ahead and get some Permatex

 

[Stirlingmoz]

I’m going to fess up here.

I installed a paper gasket when I did my G/S rebuild.

I gave the gasket a light buttering on both faces with grease and bolted the final drive up. Never had a weep / leak here.

I believe the monos have a gasket and they’re not hugely different in final drive / rear suspension engineering terms.

The monos came after the early G/S’s and ST’s so maybe this was an improvement to address potential leaks ?

I’m happy with my gasket

 

[sidkn33]

I’m going to fess up here.

I installed a paper gasket when I did my G/S rebuild.

Sacrilege!
But thanks for the brave confession, especially here.
You'd better read three chapters of a Haynes manual and one of Clymer as penance.

 

[mikeyboy]

G/s and st
Earlier bikes had a gasket,later did not.
Happy to be corrected but the gasket delete seemed to coincide with the crown wheel bearing changing from roller to a taper roller.
They also deleted the gasket between the final drive casings at the same time.( there could be a number of reasons for the changes,but I’d bet on cheaper production costs)
Early units have a “top hat” pressed/glued into the rh side of the casing.
Later are just solid casting.
Again, happy to be corrected but I believe one of the reasons for the gasket delete was due to a few final drives coming loose due to the gasket disintegrating.( although this may have been machines being used under very arduous conditions)
Fit one,don’t fit one,,,, makes no odds.