Airhead Engine - Bottom End Assembly - Custom BMW R90/6

The time has come on this BMW airhead project to start putting parts back on instead of taking them off!
We're starting with the lower end of the engine. The main bush bearings - front and rear - get replaced with fresh ones. A special modification is made to the front main bearing carrier to ensure the bearing stays in place. Then the crankshaft gets installed next and the endplay is measured to ensure everything is where it needs to be.
Finally, the camshaft is installed followed by the timing chain. A slight mis-step with parts ordering stalls us momentarily - there are two kinds of oil pump inner rotor and we have the wrong one! The correct piece is ordered - wait for part two of the engine assembly to see that!
Want to see more of the Custom BMW R90/6 Project? Check out the playlist here:
• BMW R90/6 Custom build
I'm on Instagram @roodlum / roodlum
Parts made right here in Rochester, NY are available here:
shop.themotowo...

[@massimofigna8721]

I’m restoring a R90S and your video is great as i’m exactly at that stage.
Thanks and well done

[@roodlum]

Thanks! Good luck with your project!

[@wheeldz4937]

the best one

[@wheeldz4937]

This has been very helpful... Thank you very much

[@nathansunshine9453]

Great Video! I learned a lot of useful stuff that will come in handy in my near-future rebuild. Thanks!

[@roodlum]

Glad you enjoyed it! Make sure you do a lot of reading before you get into it!

[@D3vtsb]

Looking great mate!

[@roodlum]

Cheers!

[@cozydram1]

did you need to replace the thrust washers? or reuse exciting?? please and thank you

[@roodlum]

I believe I was able to re-use these ones though I had bought extras just in case things didn't measure out correctly.

[@rogerstenbro1051]

Hi
If the endplay is too large, where do you put the shims?

[@roodlum]

The shims sit on either side of the rear of the case. You'll need to remove the crankshaft to access the one on the inside, but the other is behind the flywheel and rear main seal.

[@9jasonwhite]

Love this video! Curious do you always need to replace the Main Bearings, Front and Rear when disassembling the motor? I have my motor all the way bare, down to just the casing and rear main bearing. The Front main bearing remains inside the carrier. I'm going to clean the casing and vapor hone it. But will seal it prior to and clean after the vapor honing process. Should I replace my rear main bearing, minimum? or do I need to replace both?

[@roodlum]

I'd say main bearings only necessitate replacement if there is scoring or other visible wear on them. In our case, the bearings were borderline. There was likely many many more miles of life left on them, but considering all the parts and effort going into this bike and the pitting found on the rockers and lifters, we felt it was worth it to change them out while we had the engine apart. As you probably saw though, it's a rather involved process.

[@9jasonwhite]

@@roodlum Yes! This definitely answers my question/email. Again, an amazing video. Great work! I'm subscribed!

[@Te4mUp]

Hey so I'm looking to get my engine parts vapor blasted and then powdercoated. Should I remove the rear main bearing insert prior? Also, any idea what temperature I should measure the main bearings at? I'm not seeing this stated in my Clymer manual at all...

[@roodlum]

I'd probably leave it in and inspect it afterwards. I'd suggest getting an official BMW manual if you're going that far into the motor. I think I heated the block to around 350F, it took a while.