Main seal?

[srankin]

I was inspecting a bike for sale with a friend. We wanted to check the valve clearances and found the timing marks were off. The bike was in good shape for the price and my friend bought it. later when we did a rear main seal we moved the flywheel back to where it should have been. Previous owner's disease. St.

[San Arthur]

I was inspecting a bike for sale with a friend. We wanted to check the valve clearances and found the timing marks were off. The bike was in good shape for the price and my friend bought it. later when we did a rear main seal we moved the flywheel back to where it should have been. Previous owner's disease. St.

Harsh punishment for moving the flywheel from where it should be… Will correct mine as soon as I get the o-ring

[srankin]

It wasn't the end of the world, no harm done, just confusing. I have seen worse, LOL. St.

[San Arthur]

It took some effort to remove the helical gear wheel, I damaged the shaft seal (11311256861) in the process.

Next, I turned my attention to the main crankshaft seal. Using the proper tool made this job straightforward, and I was able to replace the seal with ease. Having the right tools truly makes a world of difference.








After replacing the crankshaft seal, I reinstalled the flywheel and installed a new seal ring to ensure a proper seal around the flywheel mounting area. Once the flywheel was back in place, I rotated it using the bolts to check alignment.





I’m happy to report that after careful adjustments, the OT mark now aligns perfectly with the engine at Top Dead Center (TDC), as it should.

[San Arthur]

Reinstalling the Oil Sump and Preparing the Engine for Removal



Before removing the engine from the frame, I decided to reinstall the oil sump and cover it to prevent scratches during the process.

By using the sump as a base, I could safely place the engine on the workbench for further work. It’s a small detail, but these precautions can save a lot of frustration later.

For the reinstallation, I followed Snowbum’s guidance on proper torque values and tightening methods.


I’m in no rush, so I took the time to carefully chart the bolt positions, create a numbered graph for reference, and ensure consistency.


While I admit I may have gone a bit overboard cross-tightening the new bolts, it was an enjoyable part of the process.

[San Arthur]

Finding a Vapor Blasting Specialist

As part of restoring the R90S, I needed the engine covers cleaned and restored. Vapor blasting was the obvious choice to bring out the original satin finish of the aluminum. After searching everywhere, I came across a young entrepreneur who recently started a vapor blasting business.



He’s a third-generation motorcyclist and hot rodder who grew up around classic machines. Turning that passion into a business, he’s helping keep vintage motorcycles alive. It’s exciting to see someone from the next generation embracing restoration and giving parts the care they deserve.

The Results



The engine covers came back looking incredible. Vapor blasting removed years of grime and oxidation while preserving the original texture, leaving a smooth, factory-like finish. Seeing those parts restored reminded me why I love this process—it’s about bringing life back to the details that make these bikes special.

Supporting Passionate Craftsmanship



It’s inspiring to support someone who shares our enthusiasm for classic motorcycles and is dedicated to keeping this tradition alive. If you’re considering vapor blasting, seek out someone skilled and passionate. It makes all the difference in the results and keeps the spirit of our community going strong.

[srankin]

You are making good progress. LOL, more than I am in my project. I am stalled at degreasing a bunch of baked on oil leaks and grease. My parts washer doesn't dent the stuff. How I wish it were warmer outside so I could use a pressure washer. St.

[San Arthur]

You are making good progress. LOL, more than I am in my project. I am stalled at degreasing a bunch of baked on oil leaks and grease. My parts washer doesn't dent the stuff. How I wish it were warmer outside so I could use a pressure washer. St.

Thanks, St.! Progress has been steady, but I hear you—cold weather slows everything down. The vapor blaster mentioned they drained their tank expecting freezing temps, so they’ll continue in the near future. In my garage, it’s so cold my hands don’t have enough dexterity for fine work either. Feels like I’m wearing mittens, hahah!

It’s also too cold to paint the cylinders right now, even though they’re already cleaned, degreased, and prepped for the final coat.

[San Arthur]

Before reinstalling the clutch, I decided to replace the timing chain. The original infinity-style chain had been in service long enough, and it was time for a fresh start. I carefully cut the links to remove the old chain and installed the new one.





With the timing chain sorted, I moved on to reinstalling the clutch.



The process went smoothly, thanks to the centering tool, which is absolutely essential. Trying to align the clutch disk perfectly without it would’ve been a nightmare!




As I worked, I couldn’t help but recall a moment years ago with a friend, an MB mechanic. I watched him frantically search his garage for his “magic spline lube,” only to find it and apply just a tiny smear before closing up the assembly. At the time, I thought it was just a quirky ritual or lucky charm for a part that might never see the light of day again.



Now, here I am doing the same thing—waiting a whole week for my Staburags NBU 30 PTM to arrive so I could apply it properly to the clutch diaphragm spring tips. A small detail, sure, but one that ensures long-term reliability and smooth operation.



Once the Staburags arrived, I applied it sparingly to the diaphragm spring tips, ensuring even coverage without overdoing it. With the clutch centered and everything torqued down in sequence, it was satisfying to see it all come together.



A few miles ago, I upgraded the fork springs to improve the front suspension performance. But now, as part of this full restoration, I’ve decided to dismantle the suspension again to restore everything back to its original setup—because why not, hahahaha!

I drained the fork oil (which was darker than I’d hoped) and let it sit to make sure everything is as clean as possible before disassembly. The darkening of the oil isn’t due to mileage—it’s only been a few miles since the change—but more likely from contaminants left in the system or the natural aging process of the oil.