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tunnelrider
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New swing arm/ final drive gasket
10/12/18 at 06:28:55
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Hi everyone,

Symptom is a weeping swing arm / final drive join. It's not coming from the drain plug or filler plug.
Should I use gasket sealant when I replace this gasket? I ask this because some BMW gaskets don't require any sealant. The new gasket is from Motobins.
If there's likely to be another reason for the weeping please ignore my naivety.
Thanks in advance for any information.
  

Swing_arm-final_drive_weep.jpg ( 951 KB | 3 Downloads )
Swing_arm-final_drive_weep.jpg

 1985 Black R65  -  1983 Ducati Pantah 500 - 2001 DRZ400 dirt only
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georgesgiralt
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Re: New swing arm/ final drive gasket
Reply #1 - 10/12/18 at 12:30:45
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Hello,
I've dismantled this part of the bile in order to powder coat the whole swing arm (and frame..).
The final drive had been put back with the plain paper gasket without anything and no leaks.
I used the proper torque to assemble the drive.
Hope this helps.
  
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Tony Smith
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Re: New swing arm/ final drive gasket
Reply #2 - 10/12/18 at 16:30:12
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BMW Engineers would have coniptions at the idea of you putting sealant on that gasket.

The reason is that the crushed thickness of that gasket has been carefully calculated so that the correct dimensions of the swing arm are maintained and the rear axle is true relative to the frame of the bike.

Or at least this is how it was explained to me by a now departed guru of all things BMW.

The reality is that this is another case of BMW stressing out to ensure a solution to a non problem. i would happily use a thin smear of a non-hardening jointing compound such as Hylomar and be confident the wheel alignment would not be affected.

BUT, if you clean the joint faces and use a new gasket, and then tighten the bolts to the correct torque, you don't need jointing compound.
  

1978 R100RS| 1984 R65 | 1984 XT350 | 1992 KLE500 | 2002 R1150GSA
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Mrclubike
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Re: New swing arm/ final drive gasket
Reply #3 - 10/12/18 at 18:42:54
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just make sure the axle is installed and snugged up
to make sure the axle bores are in line when you tighten the 4 bolts
Yes use some gasket sealer sparingly and use the gasket
  

Buzzing along on my tubeless 82 R65
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tunnelrider
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Re: New swing arm/ final drive gasket
Reply #4 - 10/15/18 at 05:44:19
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Interesting job. Has posed more questions for me than the one answer for the leak, about how the whole swing arm and final drive set up works, considering the amount of abuse it gets. It was leaking from a sharp edge on the final drive face wearing through the gasket, not sure how that got there. Kinda looked like it'd copped a sharp stone from the side at the join (could be me), or a screw driver to pry open from the side (def not me). First thing -

On the twinshock final drive shock mount, what should be protecting the final drive housing from the shock absorber? A washer of some sort? Mine's got nothing currently.

Not sure if the Motobins gasket is as thick at the paper gasket on there before.

- This could lead to a new wear pattern on the coupling splines, not the end of the world as they have a lot of life left. On taking the diff off, the shaft/ rear drive coupling splines were wet with oil and otherwise clean. Black mark in the middle of the swing arm female splines from the drive splines.
Clymer says lube the splines on reinstall so I dutifully lubed the splines on the swing arm and drive couplings with high moly but wonder how long that stays on for considering the area is full of gear oil, does it get hot and it all goes out in the next oil change?
  

 1985 Black R65  -  1983 Ducati Pantah 500 - 2001 DRZ400 dirt only
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Justin B.
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Re: New swing arm/ final drive gasket
Reply #5 - 10/18/18 at 14:01:41
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Not sure what has happened here but something got screwed up after this post.  Some sort of date stamp didn't match up in a quote, or something.  I couldn't really figure out what was causing this so I just deleted the replies starting where the error occurred.

Sorry...
  

Justin B.

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1981 R100RT - Summer bike, NEKKID!!!
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