Workshop Rebuild

To remove the last few bearings from the BMW R100 final drive, a set of specialty pullers are required…
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The needle bearing comes out first with very little effort, followed by the radial ball bearing located behind the ring gear.
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The large oil seal is then pressed out of the cover, allowing all components to be laid out on the table for inspection.
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Two issues immediately caught my attention, one being the front needle bearing race.
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It appears to have shifted over time and has started contacting the inside of the final drive housing.
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If left as is, it would continue to wear and eventually introduce metal debris into the bearing.
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In the previous video, I found a small piece of steel that may have passed through the gears, as there is slight discoloration visible on a few teeth.
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There is no major damage, but it could have turned into a much bigger issue.
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Now it is time to wait for new parts, thoroughly clean everything, and prepare for reassembly.

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.

Before tearing down the BMW R100 mono final drive, I needed to clean it up and capture scan data first.
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Those files let me bring everything into a digital assembly, dial in exact fitment, and start prototyping with confidence.
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Since this final drive will get a few tasteful modifications, I want full control over how the rear wheel hub looks.
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I’ll model different designs, print them, and test-fit each version on the rear end.
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It’s a small step that will have a big impact, not just on this build, but on how future customs of mine take shape.

Finding a mono-style BMW R100 final drive isn’t the hardest task, but tracking down one with a specific ratio is getting more difficult these days…
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I managed to source this one from the other side of Canada, thanks to
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While everything looks good on the outside, I still want to verify that it’s within spec and go through it with a full internal overhaul
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Here’s a quick look at how I confirm the ratio before tearing into it

The 1970s BMW headlight bucket used a unique, vintage key for the ignition switch…
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To recreate the same functionality as the original headlight bucket, I had to get a bit creative.
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My goal was to develop a clean and straightforward solution to securely mount the terminal board inside the bucket.
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In the original design, the cradle tabs are known to weaken or break during servicing, making this area particularly delicate to work on.
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That led me to the idea of using zip-ties to my advantage. They are widely available, easy to install, and inexpensive to replace if needed.
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After developing a custom approach, the ignition switch operates flawlessly, and the terminal board sits securely within the redesigned headlight bucket.
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I refined the holding ring through three iterations, and the final result of this system performs exactly as intended.
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This gives me confidence to carry the design into the final version, where it will undergo further testing.
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Let me know what you think of this approach and whether you believe it will hold up.

Bringing a 1970s BMW /5 series headlight bucket to life, but with a modern twist.
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Over the past few days, I scanned and reverse engineered the original part, then brought it into the digital world to refine and improve key features that were never designed with serviceability in mind.
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This first version was printed in PLA on the P2S to validate geometry, fitment, and function before moving into a more durable engineering material.
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The goal is simple:
• Maintain original external appearance
• Improve internal usability and serviceability
• Create a part that can be reproduced, repaired, and actually used

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From dialing in bezel fitment, to designing snap-in clips, to choosing mechanical fastening solutions like tee nuts over heat-set inserts, every detail is being tested and refined.
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Even components like the speedometer and ignition lock assembly were carefully evaluated to ensure proper fit and smooth operation.
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More details on the internal design and next iterations coming soon