Workshop Rebuild
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Removing the ring gear was the easy part… the real challenge came right after.
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Extracting the pinion shaft without causing any damage turned out to be far more involved than expected, especially since it appeared this assembly had never been apart before.
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Even with the correct tools on hand, I had to adapt and come up with new holding methods to keep everything secure. The pinion was seated incredibly tight and everything took more effort than expected.
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Applying controlled heat and working it free step by step made all the difference, but it was one of those moments where patience mattered more than force.
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Once everything was finally apart, the front section of the pinion shaft immediately stood out to me and raised some concerns.
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I am very glad I took the time to go this deep, because reinstalling this unit without a full inspection and service could have led to serious issues down the road, even though the drive initially felt smooth and acceptable during a quick check.
Purchasing used parts online always carries some risk, especially when it’s a 30+ year old assembly with an unknown history…
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This BMW R100 mono final drive is due for a full overhaul, and that starts with a complete teardown.
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During disassembly, I pay close attention to all rotating and sliding components to get a clear sense of the overall condition.
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Once you understand how parts fit and feel, it becomes easier to tell what they’re lacking, or if they’re still in good shape.
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As I worked through this unit, it became clear the cover had been opened before… the RTV silicone gave that away.
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Not necessarily a bad thing, just something to note.
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The ring gear and pinion are in solid, usable condition, which is definitely a relief.
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However, when I spun the pinion shaft, something didn’t sound quite right… that’ll need a closer look.
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The contaminated oil also raised some concerns, and sure enough, I found a small steel fragment inside.
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It had been flattened, which means it went through the moving parts somewhere…
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Not sure where it came from yet, but it’s something I’ll be digging into further.
03/31/2026
It’s not perfect, and that’s totally fine! The BMW /5 headlight bucket was scanned and converted into a solid model, then refined with features that make it fully 3D printable while improving on certain areas.
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This is Version 1. The print ran flawlessly, but I could have pushed the settings a bit further toward surface quality to get an even cleaner outer finish.
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Functionally, it’s right where it needs to be. Only minor refinements from here, nothing major.
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Test fitting with original components shows strong alignment. The geometry is clean, and everything sits where it should.
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The speedometer fits snug, the bezel clicks in place, the ignition cover sits properly, and the slider mechanism works exactly as intended.
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From here, it’s about refinement. Dialing in print settings for a near zero post process finish, and optimizing internal features to reduce print time without sacrificing strength.
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This is shaping up to be a solid solution. Next step is producing an improved example and then printing in outdoor ready materials so they can hold up properly on a bike.
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Edmonton, AB
