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Old 05-01-2013, 07:25 PM   #46
bmweuro OP
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Here is a picture of both rods.

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Old 05-01-2013, 08:05 PM   #47
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Nothing out of the ordinary to my eye bmweuro.
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Old 05-01-2013, 08:29 PM   #48
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Nothing out of the ordinary to my eye bmweuro.
The left wrist pin slid out a little to easy and the right took a little persuading. The left rod small end is pretty beat up.
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Old 05-01-2013, 08:37 PM   #49
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Originally Posted by bmweuro View Post
The left wrist pin slid out a little to easy and the right took a little persuading. The left rod small end is pretty beat up.
What do the crank journals measure?

What does some plastigauge say about the big end clearance?

What does the small end measure? (you replace those bearings sometimes too.)

What do the pins measure?

What about the piston OD, cylinder and taper?

Bore ID, cylinder and taper?
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Old 05-02-2013, 07:48 AM   #50
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Quote:
Originally Posted by bmweuro View Post
Here is a picture of both rods.

[IMG]https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-frc1/485543_527117007334126_1992627147_n.jpg[/snip]
Not bad-looking enough to be knocking. IMO.

Puzzling. Make some measurements.

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Old 05-02-2013, 10:33 AM   #51
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It looks like the problem was not rod bearings. Also, 30 psi at 1100 rpm and 70 psi at 3000 rpm is good oil pressure. Are you sure the problem is not pre-detonation knocking? How do the heads and pistons look - is there a lot of carbon? Any indication that the valves are contacting the piston (or carbon on the piston)? Could this be a piston slap problem? Now is the time to address any and all of these (somewhat unlikely) causes. Could this 'knock' be timing chain slap? Good luck!
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Old 05-19-2013, 10:26 PM   #52
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Originally Posted by Stan_R80/7 View Post
It looks like the problem was not rod bearings. Also, 30 psi at 1100 rpm and 70 psi at 3000 rpm is good oil pressure. Are you sure the problem is not pre-detonation knocking? How do the heads and pistons look - is there a lot of carbon? Any indication that the valves are contacting the piston (or carbon on the piston)? Could this be a piston slap problem? Now is the time to address any and all of these (somewhat unlikely) causes. Could this 'knock' be timing chain slap? Good luck!
I raised the needle position up one notch and now it runs a little rich and took it for a good ride today. The noise is back. So I have oil pressure, timing is correct, fuel mixture good.
I don't think it's the timing chain because you would here it at idle. I'm starting to wonder if there is something rattling under the tan or next to the starter.
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Old 05-19-2013, 10:46 PM   #53
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Originally Posted by bmweuro View Post
I raised the needle position up one notch and now it runs a little rich and took it for a good ride today. The noise is back. So I have oil pressure, timing is correct, fuel mixture good.
I don't think it's the timing chain because you would here it at idle. I'm starting to wonder if there is something rattling under the tan or next to the starter.
Did you measure up everything before you put it all back together?
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Old 05-19-2013, 11:29 PM   #54
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Did you measure up everything before you put it all back together?
The motor measured out like it had very low miles.
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Old 05-19-2013, 11:40 PM   #55
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The motor measured out like it had very low miles.
Run a tank of high test. That will put detonation to bed.

Then work on making it knock at idle. If you can find a big deserted parking lot, try it without a helmet and bounce it around. You may well find something to your 'something rattling' theory.
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Old 05-20-2013, 12:46 AM   #56
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Run a tank of high test. That will put detonation to bed.

Then work on making it knock at idle. If you can find a big deserted parking lot, try it without a helmet and bounce it around. You may well find something to your 'something rattling' theory.
I only run 91 octane and I have been riding it around the shop without a helmet for weeks trying to pin point it.
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Old 05-20-2013, 02:01 AM   #57
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I only run 91 octane and I have been riding it around the shop without a helmet for weeks trying to pin point it.
Check plugs w/ magnifying glass for signs of detonation (typically the insulation is white with tiny beads of molten metal).


Unless you just want a shop bike, try a parking lot, a bumpy one.

Check the usual suspects: missing center stand bumpers, Ovalised shock bolts, loose subframe bolts, loose battery box bolts, any bolt on the front end, coil mounts, etc.
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Old 05-20-2013, 03:47 AM   #58
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I don't know how old the bike is but, the original timing chain tensioner fitted to the single timing chains, used to make a bloody awful noise when worn, BMW later rejigged the design and the problem went away.
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Old 05-21-2013, 11:52 AM   #59
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Update.

I checked the jetting and 170 mains, 45 idle. I raised the needle one notch. Still runs fine and I can start it without the chokes on. I pulled the plugs and they look a little on the lean side. The motor is a 1976 R90/6 with 40mm Bings(odd combo).
Still trying to find the noise.
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Old 05-21-2013, 11:59 AM   #60
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from another forum:

http://forum.bmw-club.org.uk/viewtopic.php?t=28150
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