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Old 01-07-2010, 11:37 AM   #1
squirrelscoundrel OP
beginner metal jockey
 
Joined: Apr 2009
Location: Fabulous Rhode Island
Oddometer: 45
a bunch of airhead questions for all you experts. Thanks in advance.

So I have my bike in pieces and am wondering what to do next. The engine is out, I have a gasket kit on the ready but am wondering about other jobs that I should while it is apart. History: 70,000 miles 1974 r75/6. The bike sat for 5 years. previous owner said it was well mantained... who knows

Questions:
How do I know if the timing chain needs to be replaced? Can I know this without taking the whole engine apart?

How do I know if the cam shaft bearing needs to be replaced? Can I know this without taking the whole engine apart?

The cylinders look really shiny and are free of any visible imperfections (this is my first time ever seeing a cylinder, but I am amazed by how clean they are) So should I do anything to the rings or the pistons? i.e. hone and replace?

I have attached a pic of one of the cylinders...if it helps.Photobucket

Thanks a lot for the help. This is the link to my thread. Thanks again!
http://www.advrider.com/forums/showthread.php?t=524199

Doug
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Old 01-07-2010, 12:29 PM   #2
ChromeSux
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Location: Lenoir City TN.
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Anton or some of the other guys can give you the exacts but if i went thru all the trouble and took it down as far as you have i would go ahead and do the entire motor too, i know there are many BMW out there with allot more miles on the motor bottom end but if you are going to keep it why not do it right.
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Old 01-07-2010, 12:34 PM   #3
crazydrummerdude
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When I saw my first cylinders, I was surprised how shiney they were, too.

With a more mature eye, I can now see carbon ridges and imperfections, etc. We'd need a better pic to assess yours.

If you're on a budget, like I've always been, I would not worry about the bearings you mentioned just yet. I'd ride it and keep an eye/ear out, for sure, though. If you have infinite time/money, or infinitely more than me, sure, tear it completely down while you're in there. Then, you at least know what you've got when you've got it all back together.

What I did to both my resurrected BMW's was hone the cylinders and put in new rings.
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Old 01-07-2010, 12:49 PM   #4
batoutoflahonda
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Joined: Aug 2007
Location: Easton Wa
Oddometer: 1,362
Timing chain

http://bmwmotorcycletech.info/timingchain.htm

more info from Snowbum:

http://bmwmotorcycletech.info/techindex.htm
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Old 01-07-2010, 12:58 PM   #5
DUNDERHEAD
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Did you try to start the bike prior to tearing it down ?
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Old 01-07-2010, 01:12 PM   #6
Wirespokes
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Location: Jackson's Bottom Oregon
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That's the best reason to start it up before tearing into it like this - a running assessment will point out things like smoking, rough running, low compression, knocking, tapping, scraping or other out-of-place sounds.

The timing chain may be ready or it may not, but it's easy enough to get at with the engine mounted. But this is about the mileage they tend to go, so could be a good time to replace it. And they're cheap, so why not?

I wouldn't worry about any of the bearings, if it wasn't run low on oil they should be fine.

As for the pistons and rings - there's another item that's just so easy to get at that I wouldn't worry. If it's working, don't fix it! I don't see any scraps or broken stuff, so just clean it up, replace the push-rod seals, stick the pistons back in and go. The head gaskets are re-useable, so the whole thing could be torn back apart next week if need be if for some reason you needed to get back in there, without needing to replace gaskets.

Most of these parts last so long, that even if it's got only 20K life left, that's three or four years for most riders. Why get impatient? Spend the money on a good set of tires, or nice rear shocks, or for some better riding gear.
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