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Old 03-25-2014, 02:53 PM   #1
billmo OP
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R90/6 different style heads?

Hello All -
I am new to this forum and new to being an airhead owner. I just picked up a 1976 R90/6 in copper with gold stripes. It had previously dropped a valve while idling and needs a new head, among other things. It came with a replacement used head but that head is different than the original. The area where the rockers bolt down to the head is clearly not the same. The rocker bases do not fit snuggly on the skinnier mounts(third photo). I see both styles advertised on ebay and am wondering what the difference is. Also, the PO had begun sanding the gas tank because he didn't like the original color and now I am forced to find matching paint. I believe it is #511 Havana Gold. Any advice?

https://www.dropbox.com/sc/y66ryocqghdd4w7/RoK5YpE5Ml

billmo screwed with this post 03-25-2014 at 04:15 PM Reason: photos wouldn't load
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Old 03-25-2014, 04:08 PM   #2
Big Bamboo
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Everything you need to know about rockers: http://largiader.com/tech/rockers/ Sorry, can't help you on the paint and your pictures don't show.
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Old 03-25-2014, 05:01 PM   #3
Bill Harris
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Very good, BB-- Anton's page is a standard reference.

BMW paint colors are defined as Glasurit codes-- here is a website with a listing of the paint codes:

http://bmwmotorcycletech.info/pcodes.htm

Or just Google "glasurit bmw motorcycle paint codes" for more concise (but less colorful) info... :)

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Old 03-25-2014, 05:21 PM   #4
disston
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You may end up having to mix the rocker styles to use different vintage heads. You'll be able to figure that out using the info on Anton's pages. I wouldn't want to do this but it could work. You might have to find another set of rockers. You may.

But you should not mix different size valves. Over the years both intake and exhaust valves come with different sized heads on the valves. I think you can see the difference if you look. Or measure.

Maybe somebody else thinks mixing valve sizes would be OK. I don't.
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Old 03-25-2014, 05:47 PM   #5
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I have seen all sorts of /6's with mismatched rocker arm components. It will work. Just barely. A lot of /6's that you hear that sound like cement mixers probably have some mismatched rocker arm components. Despite what Anton's sight says, /6's came with three different rocker arm setups. The very early ones had /5 bushed rocker arms. Also, the '85 on setups very much can in fact be adjusted by pressing the rocker arm blocks together. Don't even try?? I have done it hundreds of times as have many other mechanics I know.
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Old 03-25-2014, 09:39 PM   #6
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No advice other to say listen to these people.

Welcome to the asylum, Bubs. I love my R90/6--hope everything works out.
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Old 03-26-2014, 07:33 PM   #7
billmo OP
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Well I read Anton's page and he says you can take the posts from a 1976 /6 and put them in the recessed areas of an earlier /6. However that would leave a large chamber where the old longer posts would have sat that would need to fill with oil before feeding the rockers, every time you start the engine. He also stated the rockers are fed with oil that is low flow so I'm thinking it might take a while to fill these chambers. Just wondering if I would be doing my rockers a disservice by swapping these parts. Any thoughts?
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Old 03-26-2014, 07:58 PM   #8
knary
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Quote:
Originally Posted by supershaft View Post
I have seen all sorts of /6's with mismatched rocker arm components. It will work. Just barely. A lot of /6's that you hear that sound like cement mixers probably have some mismatched rocker arm components. Despite what Anton's sight says, /6's came with three different rocker arm setups. The very early ones had /5 bushed rocker arms. Also, the '85 on setups very much can in fact be adjusted by pressing the rocker arm blocks together. Don't even try?? I have done it hundreds of times as have many other mechanics I know.
All I know is that on my mismatched /7, the stock rockers on one side are reasonably quiet and the aftermarket on the other, which may or may not be a mismatch of stock and luftmeister parts, is distressingly noisy.
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Old 03-26-2014, 08:15 PM   #9
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Just found this on ebay. A bit pricey, but considering it's an original in a rare color... I'd make an offer and see what he says http://www.ebay.com/itm/BMW-Sport-Ga...item56555229db
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Old 03-26-2014, 09:23 PM   #10
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Nice looking tank.... but Yikes....like you said, pretty pricey.
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Old 03-27-2014, 07:25 AM   #11
AntonLargiader
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I'm saying you can retrofit each style rocker back one generation. Only you can see what your bike has; the applicability dates are not meant to be definitive. Some very early /6 models had exposed-tube heads and would have needed the sleeves and O-rings. I think some late /5s had enclosed tubes. You have to see what you actually have.

I don't see the concern you have about the oil cavity, but I'm really not sure what you mean. Where is this big chamber that needs to fill?



Quote:
Originally Posted by billmo View Post
Well I read Anton's page and he says you can take the posts from a 1976 /6 and put them in the recessed areas of an earlier /6. However that would leave a large chamber where the old longer posts would have sat that would need to fill with oil before feeding the rockers, every time you start the engine. He also stated the rockers are fed with oil that is low flow so I'm thinking it might take a while to fill these chambers. Just wondering if I would be doing my rockers a disservice by swapping these parts. Any thoughts?
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Old 03-27-2014, 03:51 PM   #12
billmo OP
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I tried to remove the posts from my early /6 head and the piece that came out was approx. 3" long and when it is not installed it leaves a round shaft approx. 3/4" in diameter that runs almost the entire depth of the head. I assumed if the oil is fed through the top bolt channels that that area will need to fill with oil before it gets forced to the rockers. Is that not correct? If this is indeed a low flow of oil then I assumed it would take a little while for it to fill and since the area to be filled with the original 3" piece installed would be much less I thought the rockers would be starved for oil. The impression I got from your website was that I remove the 3" sleeve(the one that is pressed in, not the one with the seals) and then I just put the button style(later /6) in the hole that is left. Maybe (a) I am not understanding how this works or (b) I am concerned about something that is actually insignificant.
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Old 03-27-2014, 04:18 PM   #13
AntonLargiader
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The sleeve goes over the post to compress the O-ring in the head on early bikes. The 1st version shows the sleeve in place, the 2nd shows it missing and only the post is left, If you remove the entire support post (which you say you did) then sure you have a great big hole. You can't use the head that way, partly because it's wronger than wrong and partly because there is nothing for the rocker to sit on.

Hopefully you can reinstall the post.
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Old 03-27-2014, 05:21 PM   #14
robtg
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No wonder there are as many fucked up old airheads as there are running
around.
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Old 03-27-2014, 05:27 PM   #15
Bill Harris
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Or not running...

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