Engine case bearing bore markings

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concours

concours

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To the many here who've had many bottoms opened up, has anyone seen this type of random marking? (timing side) It's a '73 850 case that otherwise is undamaged. Do you suppose it was a totally rusted solid bearing and the crank was twisted back and forth to remove it? (rust is evident on other steel areas)

Engine case bearing bore markings


Engine case bearing bore markings



The other side (drive side) shows the expected marks from boring, and the mark from the bearing outer race living there for some time.
Engine case bearing bore markings


Engine case bearing bore markings
 
I use a jewelers eye glass to check near everything, last time I saw patterns like that was in my 74's (cracked) transmission case bearing bores.
How hard was the bearing to remove I wonder.
 
Not an obvious spin pattern with those random patterns rather than machined like parallel score marks. If bearing took some good heat to drop out maybe it spun or rattled in a way to sort of gall into self knurling to take up slack. Loctite is a joke there even comnoz says try good ole JBW original formula as 1st attempt if even needed. Machined in peg/screw is the 2nd to hardest best way, 1st being to get something non norton of course.
 
I remember seeing wallowed out bearing bores in sled engines (primarily Polaris/Fuji triples that had been clutched/piped to spin 1 to 2,000 RPM above standard design) 20 years ago, but they didn't look like this 850 at all. This one shows raised metal, scores not parallel.
 
I have seen something exactly like this. The Super Blend to be replaced actually just dropped out of the case with just the very first application of heat, "WHAT-THE-HELL". The bearing had not spun but the bore with those exact marks was oversize. Up close personal inspection led us to the conclusion that someone had attempted to dress the case bore with a course file. :shock: The bore was left alone and the new bearing installed with Loctite sleeve retainer, or bearing retainer, I forget which, only that it was a high temp product suitable to keep a slip fit from moving. I'm sure Loctite's web sight will describe just the thing. As far as I know the engine never gave any trouble.
 
Looks to me like intergranular corrosion. It's when aluminium corrodes between the grains. If there has been moisture between the steel brg outer and the alu case it can cause this. You could try to scrape a small area with a Stanley knife to see how deep it goes.

You can treat it with phosphoric acid. Give it a scrub with scotch rite and water till you get a water break free surface. Water stays in a layer and doesn't ball up. Wipe dry then apply acid, leave for 60 seconds then rinse off with clean water.

Make sure it's comptletly dry befor fitting the brg. When you heat the case to fit the brg this will dry it off.
 

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If you get moisture in contact with oil, you can get cladosporium resinae growing which can cause corrosion.
 
concours said:
To the many here who've had many bottoms opened up, has anyone seen this type of random marking? (timing side) It's a '73 850 case that otherwise is undamaged. Do you suppose it was a totally rusted solid bearing and the crank was twisted back and forth to remove it? (rust is evident on other steel areas)

Engine case bearing bore markings


]
Click to expand...

This "pattern" of whatever, not spinning bearing, not dirty bearing fitting... Looks so very much like the break down of surface protection (clear powdercoat) on my 08 Triumph fork tubes..... Over normal wear and tear with stone chips and bugs etc, moisture has obviously penetrated between coating and alloy and has identical wormhole markings as above....
The only similarity here is the alloy and the visual sameness.... Maybe there is a connection but i dont know. :D :D
 
Engine case bearing bore markings


I've seen this kind of corrosion trail on wheel bearing races. Spent a minute with a magnifying glass tonight, Not the raised material I originally thought.
 
I'm still going with manually induced, not fancy corrosion. Your engine? Or recently acquired cases?
 
concours said:
I've seen this kind of corrosion trail on bearing wheel races. Spent a minute with a magnifying glass tonight, Not the raised material I originally thought.
Click to expand...

Maybe it is some form of electrolysis decay/corrosion.
The bore in my trans case still had the original 'Made in Portugal bearing, the marks look like rivers from space and show no sharp or abrupt edges or furrows.
I had wondered if it was the bearing tracking in the bore or vibration induced.
 
Tracks are depressed but not by mechanical spin motion nor install-extractions which would leave expected straight-ish scores, looks like tortuous fluid flow etching paths by pressure &or electro=chemical corrosive forces. Maybe was run w/o a good electrical earth to engine and path somehow had to cross this bearing interface? Now what ya gonna do? Bores already ecthed so just scratch up the race and JBW may work a long term treat. Its softens alot some above operating temps to remove.
 
hobot said:
Tracks are depressed but not by mechanical spin motion nor install-extractions which would leave expected straight-ish scores, looks like tortuous fluid flow etching paths by pressure &or electro=chemical corrosive forces. Maybe was run w/o a good electrical earth to engine and path somehow had to cross this bearing interface? Now what ya gonna do? Bores already ecthed so just scratch up the race and JBW may work a long term treat. Its softens alot some above operating temps to remove.
Click to expand...


Haha.. Now im not taking the piss nor being mean to your sensitive self hobot, but i laughed when JB came into the conversation and i bet it has also been done before and would most likely be sufficient to capture new bearing fitting... Alternatively it is bored out and sleeve fitted to accept bearing. JB weld or sleeve is a debate to continue ....
Also along the JBing converstaion, i just finished painting my Ducati tank and found pinhole under tank from power wire brush and thought.. $*))*&^%$# bollocks.... just finished a nice paintjob........... JB weld !!!! so blobbed a bit of "liquid steel" on the hole after cleaning the 6mm dia spot and 6 days later its still holding fuel..
No "JB Weld"is available at retail here hometown but Liquid Steel same stuff ????? is and have use it for many year in different application...

I know this has SFA to do with this topic but hobot did mention JB first :lol: :lol: :lol: :lol:
 
Hehe, watch out for your rude reflex ass-umptions - Its was JIm Comstock who recommended JBW after loctite failures for this use, not hobot just pointing it out if needed. I did search Al bearing bore wear to see many examples/reasons of it but most concerned rod shells and bearing races but none that looked like this case so mystery remains.

Engine case bearing bore markings

In an experiment at Vemasat Laboratories, Dr. C. J. Ransom created the same kind of etched furrow by shocking a thin layer of magnesium silicate
 
The rust stains on the aluminum adjacent the bearing pockets kinda suggest this was a rescue from a field?
 
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