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Old 06-27-2013, 06:31 PM   #31
Kspit OP
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Location: Oakland, CA
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Hah! Wasn't looking at all the stud holes. Just rethreaded them all and got my pistons off. 2 on the right are helicoiled, none on the left are, score! No wonder 2 of the studs on the right were 20mm or so longer... Doh

So I thought I had my 12 point male socket thing, but it is no where to be found. Going to try some local stores and a pal or two then I'll get one off amazon. I saw someone link to them in another thread, you guys are all so helpful :P

So here are the last pics of the day. Everything looks pretty damn within spec for a 70,000~ mile motorcycle.

Here is the right head + piston


And the left



The rods have only slight right to left play, and neither have any in and out play. Hopefully bearing pictures soon!

And to sign off from working today... Here is my, I wish I had a garage picture!



So many bikes, so little time...
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Old 06-28-2013, 09:37 PM   #32
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Yes! This is the happiest I have ever been after finding a toasted set of bearings in an engine... Ever!

So I found the triple square tool at my local car part warehouse, score! Got home late and decided to remove the rods and here is what I found!

Left the resolution a little big so you can maybe see some detail..., I forget sometimes people don't have a monitor as big as I do...

Left side...


A little nasty. so so condition.

And the right side...


These looks fine right? A little emery cloth action and some assembly lube and I should be good to go right?

You can even see the damn little o ring that cause all of this in the first place in that picture! Well I guess the guy behind the camera actually caused this, but still. Who likes to blame themselves?

Like everybody told me a billion times, the crank is fine, no signs of scoring at all. Couldn't get a good picture because it was pushing 9pm as I was just finishing, but I'm sure you all don't need to see another airhead crank.

So i guess now I just need to come up with a parts list. Replace every seal and gasket I removed. New rod bolts, bearings after getting the crank miced. Maybe a big end resizing? Still considering doing my timing chain but since that isn't really a job that will benefit from having the jugs off I can maybe wait to do that another day anywho.

I measured my canister depth for shits and giggles, looked at my oring a bit and decided I do not need a cover gasket, the o ring is very slightly compressed, but no flat edges at all. I have read when you lose oil pressure the right side is the first to go anywho, so it all adds up!

Thank you all again for the knowledge and navigating me in the right direction... So far...
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Old 06-28-2013, 11:27 PM   #33
shearboy2004
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#20 thread file on those exhaust threads , take your time and clean them up as best you can then a little valve grinding paste on the threads and turn the new collars on and off a few times .This will clean them up great . Wash the paste off and you should be good to go .
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Old 06-29-2013, 06:08 AM   #34
Stan_R80/7
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The exhaust threads are M52x2 mm. So, a 2mm pitch thread file will clean them up. I would plastigauge the replacement rod bearings, just to measure the clearance. Looks like you found the source of the knock. Good job!
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Old 06-29-2013, 07:50 AM   #35
Kspit OP
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@shearboy 2004 Great! I'll be starting that work after I finish degreasing EVERYTHING. I'm mostly glad this happened so I can stop the damn pushrod seal leak, and oil pan leak and all the other leaks... hah

@Stan Perfect, I'll go down to ace and see if they have anything like that, I'm always surprised by what they actually stock there.

In regard to the last few steps here. I have a very good micrometer, and know how to use it. I may even have some plastiguage somewhere... But in most instances will i nee to have my knocking side rod trued up at all? I feel like if I can finish this rebuild without setting food inside a machine shop, i cheated or something. But that is a good feeling in this case haha.

Plans for today, start de carboning and de greasing all of my parts. Clean my K75 and drink a beer or two. It isn't supposed to be around 80 today, that isn't Oakland weather!
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Old 06-29-2013, 08:40 AM   #36
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No need for plastigauge. There is only one size rod bearing unless grinding the crank is in your future and no one does that. If the journal isn't marred and it mic's out OK, run it. I would be more concerned about the rod big end being round but that takes a bore gauge.
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Old 06-29-2013, 01:07 PM   #37
disston
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Careful not to mix rod bearing caps. I see you holding both in one hand. They are matched to the rod they came from.
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Old 06-29-2013, 01:41 PM   #38
Kspit OP
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Made sure to keep them matched with their respective side! The left side bearings didn't separate from the rod pieces, but the shot right side ones all fell apart once the rod was split. I will be bringing the rods to a machine shop sometime next week to have them balanced and trued up and after that I will be collecting part numbers to bring to BMW San Francisco to get my parts en route!

Just borrowed a thread file from the local airhead guru, Dick Sullivan, and so I'll go degrease the right head so I can start cleaning them up! But maybe i'll wait until the heat dies down :X
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Old 07-07-2013, 03:04 PM   #39
Kspit OP
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Hello again!

So I sent my rods off to machine, will be a long turnaround. Not sure how long it will take to get this beast back together anywho.

So I never posted picture of my crank. I definitely want as much input on this, as much as I know what the answer may be. I like opinions, usually...

So let me explain, when the crank would be pushing the piston and rod to its furthest extent in compression or exhaust, the visible surface of the rod journal is just fine. Smooth, no discoloration. When the crank is rotated back into its furthest downward travel, there is some extremely light scarring. I have yet to take very fine emery cloth to it, but will eventually. There are light grooves, that are barely, BARELY catch-able with a fingernail; ever so fine. The only place the scratches are noticeable to my fingernail drag over is where the scorch mark is darkest, in the center of the journal.

Here is a photo of the crank in its furthest rotation to the left side of the motor


Here is a photo of the area where it splits between being smooth as can be, and a slight scorching, the oppisite side looks identical, the "bad" scorching is only in the center as shown in the previous picture.


Like I said, I know what the answer MAY be... You guys have more experience tearing these things apart and running them, so I really love the input. I know pictures and a mostly vauge description over the internet isn't the same as having the ability to inspect it with your own eyes, I do have some local experts coming by to take a looksie next week. If it comes down to it, I can easily find a crank locally I'm sure and have a professional set it in to the case, which will hamper things, and make my rebuild a bit longer, but so be it!
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Old 07-07-2013, 05:27 PM   #40
disston
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The shop will machine the rods if they know what this is about. If they call themselves a machine shop they should. The ends of the caps and/or rods where the two meet are ground so the rods big end hole is now smaller. This is then bored back to the correct size. Result is a rod big end with a round hole. The machine that does this also aligns the big end to the small end.

If you have access to another crank in better shape and will have the lower end rebuilt by someone who does this then by all means do it. The crank is damaged. It may work OK but it will not be that OK. Internal friction of this sort causes problems with how the motor runs. It's not just a mater of eating a few extra gallons of gas. It causes poor running and poor performance. As bad as those rod bearings look I would expect the main bearings don't look all that good either.

Your friends who get to actually see this may trump my opinion. I of course can't run my fingernail over the crank journal. It's just my opinion. I'm usually pretty conservative about other peoples machines and I'm pretty liberal about mine.
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Old 07-08-2013, 07:09 AM   #41
Stan_R80/7
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Quote:
Originally Posted by Kspit View Post
Hello again!

So I sent my rods off to machine, will be a long turnaround. Not sure how long it will take to get this beast back together anywho.
It looks like the crankshaft is still in the engine casing. The rods were send off to machine? What machining operation is needed on the connecting rods?

There are some folks online who have completely disassembled the engine and rebuild the lower end. The engine (and optionally transmission) need to come out of the frame to remove the crankshaft. Looks like the job is mushrooming. Good luck!
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Old 07-08-2013, 08:19 AM   #42
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I was told by my local guy to have them trued and potentially re-sized. He told me that every time he has seen an boxer lose a big end bearing the big ends were out of round. Sent them off to be cleaned up and checked for true. The machinist, who had to have been over 70, definitely knew what he was doing.

Mushrooming, potentially. I will see how well the crank cleans up I think. If I do end up just bolting it back together we will see how long it runs for I guess, and in that period time to source a new crank/find a short block to set up to be transplanted if/when she does go... Since the machine shop is so busy I have a while to figure these things out it seems. I really do wish I had a garage right about now! Damn apartment life.
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Old 07-08-2013, 09:12 AM   #43
disston
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I work on my bike on the street. When I have to have large pieces of it off for repairs I merely put a cover over it when I'm away. I've gotten away with it so far. Apartment building parking lots often have their own rules, I know.
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Old 07-08-2013, 09:57 AM   #44
Stan_R80/7
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You may want to keep an eye out for used connecting rods. It may be that only the right rod is out-of-round due to knocking and needs to be replaced. If the rod hole is honed or machined round the diameter will increase which may require a larger outside diameter bearing that also has an oversize ID.

The rod bearings that I have seen online w/BMW part numbers are only sold in oversize ID. I have never seen a BMW part number for oversize OD rod bearings, but there may be a bearing company that makes them. I would make sure the oversized (both OD and ID) rod bearings are available before spending money on truing the rods after they are checked. Good luck!
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Old 07-08-2013, 10:16 AM   #45
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Originally Posted by Stan_R80/7 View Post
You may want to keep an eye out for used connecting rods. It may be that only the right rod is out-of-round due to knocking and needs to be replaced. If the rod hole is honed or machined round the diameter will increase which may require a larger outside diameter bearing that also has an oversize ID.

The rod bearings that I have seen online w/BMW part numbers are only sold in oversize ID. I have never seen a BMW part number for oversize OD rod bearings, but there may be a bearing company that makes them. I would make sure the oversized (both OD and ID) rod bearings are available before spending money on truing the rods after they are checked. Good luck!

Resizing a rod big end involves grinding the cap and rod where they meet and then honing back out to the standard B/E bore size. Standard size bearings are then fitted.
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