1975 R90/6 Front Cover Question

Hi Folks, quick question here regarding the front timing cover on my R09/6.

The cover that came with my bike (purchased last year as a restoration project) had polished/machined ribs that I really like the looks of. However, it's pretty dinged up so I bought a used replacement that, while it is in excellent condition does not have the machining on the ribs, instead they look like they were left as cast (see pictures).

My question is, which is correct for the bike - in other words, which way would it have come from the factory? I don't have any reason to think that the cover that came with my bike isn't original, so did someone file/machine/polish the ribs, or did it come that way?

Thanks in advance.

Larry

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I have a '75 R90S, which I have owned since new. The finish on my front cover is what you have on the cover shown in your bottom photo.

Some people polish the ribs for show bikes or cafe builds. Stock was usually all bare aluminum.

Engine Cover Parts ‘74 R90/6



Parts hand cleaned, bead blasted, then sonically cleaned.

Pretty much stock, just cleaned in preparation for reassembly.

A little closer look to show texture of the casting.

Each individual piece of casting of the engine is a little different. My personal preference is to keep the differences in place. But after 40/50 years of wear and the actions of previous owners some components aren’t the same as new. Sometimes you live with it or correct it or replace it. Good luck with your project.

These parts probably have 200,000 miles of use having been risen all over the US. When bike is reassembled it should be ready for another 200,000. Most likely not by me.

beemerguru said:

Some people polish the ribs for show bikes or cafe builds. Stock was usually all bare aluminum.

Click to expand...

Thanks beemerguru, that's the info I was looking for. It looks like unpolished is the way to go for a restoration.

Too bad, I liked the look of polished ribs. Wonder if the concourse folks would knock it?

barryg, it looks like your cover is the same as the one on my bike, given that it has been media blasted. Looks like it would polish up nicely for that shiny rib look.

Thanks for the replies.
Larry

The "Concourse Folks" don't know it all!

I am one of those "it has to be "OEM Factory correct" people so I have a little insight to the thinking and reasoning that goes into the judging thing. Its one thing to have a bike that you claim is perfect and un-restored but has a few questionable and "need more research" issues that really don't fit that year and bike. You should be comfortable with a few minor modifications to your antique, vintage and classic BMW motorcycles that enhance its value and appeal to you (the owner) so long as you don't make wild claims that "its an OEM modification" and add value to the bike. As far as the question of "is it correct for the bike and year" most people can come up with a story or justification for that particular change, color, modification or special part just to fit a story.

Its always interesting and sometimes distressing to see bikes advertised as original un-restored bikes only to find a bike that is obviously a repaint, restored and modified bike that has value to the current owner and nobody else. Is it original, resto-moded or is it restored, its important to a few of us OEM Factory correct guys and we get a little frustrated when we see misleading information on bikes. Another one is the bike that has a few upgrades or performance modifications that might enhance the value, Why?

To respond to the OP's original concern I would go with what you find is the best look for your tastes and don't worry about us "correct police" people because we secretly wish we could deviate to our personalized tastes without having to explain what we did or did not do to that perfect representation of what may have been a flawed OEM product.