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Main seal?
Re: Main seal?
The perceived problem was an "out-of-spec" oil pump outer rotor OD. They checked their inventory and all of them had the same OD. Upon further research I found a UK parts dealer that reported that BMW changed their spec on that part and all of them at my supplier were within the new spec. My supplier appreciated the updated info.
I note that I've never seen the actual BMW bulletin advising of this spec change but have assumed its out there somewhere.
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Here we go again!

'58 R26 '76 R90S '88 R100RS '94 R100GS/PD
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Frame failure
While tackling the removal of the swingarm to access the gearbox and investigate the source of an oil leak, I came across a familiar issue often discussed on this forum—a typical frame failure that seems to plague many /6 models.



Initially, I considered addressing the metal fatigue crack right on the bike. However, I decided to take the more thorough approach: stripping the frame completely of all components. I’ll be taking the bare frame to Gary, who will weld the crack at his place, and then give it a fresh coat of paint.
'58 R26 '76 R90S '88 R100RS '94 R100GS/PD
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Final Drive Thread Issue

While draining and refilling the gear lube in the final drive, I discovered that the threads in the final drive case itself are stripped—not the bolts, which are in perfect condition. Here’s a picture for reference:


Since these bolts are only used for draining and filling gear lube, I wonder if this is something I can leave as-is, considering they don’t seem to require much torque. However, could there be any hydraulic pressure inside the small compartment that might stress these threads further?

My question is: should I rethread the holes to 14mm, or would it be safe to leave them as they are? Any advice or experience would be greatly appreciated!
'58 R26 '76 R90S '88 R100RS '94 R100GS/PD
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Re: Main seal?
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Re: Main seal?
Thanks for writing, machine shop or by hand? I’ve only refresh threads but never re thread to a bigger size.
'58 R26 '76 R90S '88 R100RS '94 R100GS/PD
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Re: Main seal?
I do that repair by installing Time-Serts. It makes for a robust quality repair. Heli-coils are weak for the application and the depth is not ideal for using them. Tig welding and tapping is another repair process. Yet it is cumbersome, time-consuming and not forgiving to any impurities that were not removed from the casting.
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Re: Main seal?
I should have looked a little bit more at the pictures. Sorry, St.
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Time[Serts
If I’m going to cut new threads to install the Time-Serts, why not just rethread the hole to a larger bolt size instead? Since the bolt is primarily for refilling and draining oil, and high torque doesn’t seem critical, wouldn’t this approach simplify the repair? Curious to hear your thoughts on why Time-Serts might be the better choice here.flyingtpot wrote: ↑Sat Dec 07, 2024 1:28 amFrom the pics, the majority of the threads are gone/toast, so 'cleaning up' or rethreading the current M10 threads with a tap is not feasible.
I do that repair by installing Time-Serts. It makes for a robust quality repair. Heli-coils are weak for the application and the depth is not ideal for using them. Tig welding and tapping is another repair process. Yet it is cumbersome, time-consuming and not forgiving to any impurities that were not removed from the casting.
'58 R26 '76 R90S '88 R100RS '94 R100GS/PD
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Clutch
Clutch Disk:
The clutch disk appears to have glazing on the end corner, potentially caused by oil seeping up from the engine.


I believe the recommended thickness for replacement is less than 6 mm, and my measurements confirm that it’s borderline:

Pressure Plate:
The pressure plate also looks worn out, with noticeable scuff marks and signs of fatigue:



Additionally, there is glazing and blue discoloration on the opposite side, likely from overheating:

Compression Ring:
The compression ring appears to be nearing the end of its service life, showing visible wear and fatigue:


Diaphragm Spring:
The diaphragm spring has scorch marks and will need to be replaced as well:


Next Steps:
Based on the wear and damage across these components, it seems the entire clutch assembly—including the disk, pressure plate, compression ring, and diaphragm spring—will need replacing. I’d appreciate any advice or recommendations on parts and ensuring the engine isn’t leaking oil into the clutch housing again.
What do you think caused the uneven wear of the clutch disk?
Thank you for any insights!
'58 R26 '76 R90S '88 R100RS '94 R100GS/PD