Metal sliver in oil -- time to panic?

The send to address is “buttmunch”?

1973x75 said:

The send to address is “buttmunch”?

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Lol I noticed that too. I think the owner who commissioned the rebuild was a US service member stationed in Germany so maybe he addressed it to his base nickname.

Maybe the old owner was a practical joker?

"47mm Wiseco pistons?"

An 850 Mk3 has a std bore of 77mm

No signs of a metallic signature anywhere else in the oil?
An airplane mechanic taught me that draining an oil filter into clear glass dish and then use a strong bottom light while viewing oil through a magnifying glass and stirring it with a magnet can reveal metallic dust in the oil, how much can be revealing. Similar technique on the filter pleats.
To me, that piece looks like the leading edge reveals a break, snapped off, not a tear or cut.
Just a guess.
Have you considered inserting a borescope into the crankcase for a look? Obviously can't you see into all the tight spots but there's always a chance of spotting something that isn't supposed to look like that or be there.
Hope you find something that helps you figure it out.

my 2cents . . .

Looks like a bit of a crank shim washer to me. Maybe one that was installed on the outside of the crank bearing. Maybe someone wanted to satisfy the end float, without removing the bearing and placing it behind the bearing.

possm said:

"47mm Wiseco pistons?"

An 850 Mk3 has a std bore of 77mm

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Based on a quick lookup of the part number in the receipt, could have changed since then.

I do happen to own a borescope, so I used the big sump mesh hole to peek around. One thing I did notice is that chewed-up edge of the crank cheek. Though I suppose that could have been related to whatever damage prompted the first rebuild: looks like from a thrown rod?

Swiping my fingers and a rag inside the case, no sign of any metal flaking. The shim hypothesis seems very possible, though -- that's the closest-looking thing I've seen to the piece I found.

The bright nut just off center frame looks gnarled with shiny rough surfaces showing.
Maybe indicative of something unwanted?
I also see, its hard to tell, an angled "something" above the ragged edge of the right wall.
More light, somehow, difficult I know, could reveal what's in the shadows, but I lean toward the assessment that your mystery piece is a little chunk of crank shim.

My guess is could be the tab off the crank tab washer which holds the flywheel centre dowel in place (one each side, tabs on the outside of each nut).
If you rotate to BDC you may be able to see?
Edit - according to the parts diagrams not used on the Mk3, but does look a bit like the ones used on every other Commando crank

That artifact is radiused in two axi.
It looks for all in world like bearing cage. (I've been involved in stamping metal since 1977)

LIKELY left over from the rebuild of extensive failure.

No way to be sure unless you strip the engine.

OP, what are YOU willing to wager?

(Not likely to suddenly lock up, but get way, way worse sounding before it does, so a monetary/convenience wager)

Crank shim is the most logical. If it is, there is more somewhere.

Looking through your paperwork I don't see any evidence the cases where split.
Looks like a top end job, probably insitu. Till the crank shim came up, I was leaning that maybe something fell in the cases when the barrels where off.
Interesting note is the followers where radiused. This is usually done with a new Performance cam. Cases need to be split for cam replacement.
Again, I don't see any evidence of that. But then again, I don't read German or whatever language that is.
FYI, Mark 3's are known for 'Soft' cams. Chances are it's been replaced at some time.
What to do, what to do.

It may just fine ridden moderately. Where's the fun in that. Myself, I hammer it hard, as they should be.
Having lived through a Flywheel exiting the case, I would be at least pulling the barrels and pistons for a look see.
Having gone that far I'm sure I would pull the lower end to split the cases for a thorough inspection.
Well, might as well vapor blast the cases, respray the barrels, polish the alloys....

Since the primary is apart, good time to check the Layshaft bearing on the trans.
Might as wheel blast and clean it up also.

Since the trans is out, Might as well replace or at least inspect the Iso's.

When all this is completed, you'll have a well sorted Commando that you'll have confidence in.

Carry on......

B+Bogus said:

My guess is could be the tab off the crank tab washer which holds the flywheel centre dowel in place (one each side, tabs on the outside of each nut).

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It's a Mk3 so it doesn't have the tab washer or dowel.

Maybe we can try eliminate one or more of the ideas as to where the piece came from.

If it came from a crankshaft bearing cage, I would think that one side of it should be very polished from running with a bearing ball.
Even if the piece was tossed around a lot before finding the magnet, I would think there should be a difference in finish between the two sides.
On the other hand, it does look broken at both ends which points to possible bearing cage.
But if a bearing cage breaks, should we see part of a rivet hole in the piece?

Does anyone have an old crank ball based bearing to get some cage measurements from?
Or any old used ball bearing they are willing to pull apart to see how polished the cage is on the inside?
At the bottom of this is what I pulled off the web about cage thickness of a 6306

If it was a shim one would think the finish would be the same on both sides.
But how to explain how a rebuilder can install a crank shim and have it come loose?
My only thought here is that a crank shim could be mistakenly installed on the outside of the bearing.
because the mechanic has never worked on Nortons... But would it destruct.

Here an idea. Hammer the metal bit flat and calculate the radius of it and see how compare to a shim and cage...

The cage (or retainer) of a standard 6303 ball bearing is typically made of pressed/sheet steel. However, for this size of bearing, the pressed steel cage is generally in the range of 0.020 to 0.040 inches

DennisMo said:

If it came from a crankshaft bearing cage, I would think that one side of it should be very polished from running with a bearing ball.

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Only it should have two brass cage roller bearings.

All guesswork and could be, while hoping the engine might be ok but always wondering what if.
Eff that.
If it was mine the decision as to how to address it would already be made based on the photos....that and a foreign chunk of metal found in the crankcase.
It got in there somehow and you will never have full confidence until you tear it down....or wait until you are 70 miles away from your shop and it starts making the "uh oh" noise.
I agree completely with post #7 where Concours noted mechanical stuff doesn't fix itself.
Truly, I'm not trying to dump doom and gloom on your situation, just sharing my multiple eff up's over the years and how it influences my decisions now.

Guess don't test. Be a hero. Not meant for anyone in particular. It just makes me laugh that all the "test don't guess" people are guessing most of the time. I guess all the time before doing any testing.

That piece of metal has been in there for 20+ years hasn't it? Why hasn't the engine blown to pieces already?

Crank shims wouldn't last long enough to be in that solid shape. They are incredibly thin. Well, at least the ones I've used are. Must have been a thick one. or something that was dropped in there during a barrels off pistons and top end rebuild.

Is there anything that could get past the tach gear and get in the sump if it was dropped into the tach hole? I don't have a Norton with a tach hole in the cases, so I know nothing.

MichaelB said:

Crank shim is the most logical. If it is, there is more somewhere.

Looking through your paperwork I don't see any evidence the cases where split.
Looks like a top end job, probably insitu. Till the crank shim came up, I was leaning that maybe something fell in the cases when the barrels where off.
Interesting note is the followers where radiused. This is usually done with a new Performance cam. Cases need to be split for cam replacement.
Again, I don't see any evidence of that. But then again, I don't read German or whatever language that is.
FYI, Mark 3's are known for 'Soft' cams. Chances are it's been replaced at some time.
What to do, what to do.

It may just fine ridden moderately. Where's the fun in that. Myself, I hammer it hard, as they should be.
Having lived through a Flywheel exiting the case, I would be at least pulling the barrels and pistons for a look see.
Having gone that far I'm sure I would pull the lower end to split the cases for a thorough inspection.
Well, might as well vapor blast the cases, respray the barrels, polish the alloys....

Since the primary is apart, good time to check the Layshaft bearing on the trans.
Might as wheel blast and clean it up also.

Since the trans is out, Might as well replace or at least inspect the Iso's.

When all this is completed, you'll have a well sorted Commando that you'll have confidence in.

Carry on......

Click to expand...

There is evidence in the receipts that a 56000 cam was installed around the same time. So I think it's likely that the case was split.

I agree it should have superblends, but you never know what a mechanic might do ....

Schwany said:

Guess don't test. Be a hero. Not meant for anyone in particular. It just makes me laugh that all the "test don't guess" people are guessing most of the time. I guess all the time before doing any testing.

That piece of metal has been in there for 20+ years hasn't it? Why hasn't the engine blown to pieces already?

Crank shims wouldn't last long enough to be in that solid shape. They are incredibly thin. Well, at least the ones I've used are. Must have been a thick one. or something that was dropped in there during a barrels off pistons and top end rebuild.

Is there anything that could get past the tach gear and get in the sump if it was dropped into the tach hole? I don't have a Norton with a tach hole in the cases, so I know nothing.

Click to expand...

I think this is my dilemma. I don't necessarily mind stripping the engine down and looking directly at things to get some peace of mind and avoid big downtime and $$ rebuild bills later.

But also, this is my first Commando, and first old British bike and I've only gotten 2 rides on it. I would really like to get some seat time on the bike and get the chance to fall in love with it before committing big money and time to an elective engine rebuild.

If I did choose to take the engine apart, it would be primarily for inspection/diagnostic purposes, to make sure things are shipshape and repair any damage I find. I have little interest in going down the rabbit hole of "while you're in there" stuff like vapor blasting and whatnot, or performance modifications. My main focus is making sure nothing terrible is imminent and no glaring issues are present -- not rebuilding the engine to "like new". Hopefully I love this bike enough and put enough miles on it to want to do that some day in the future.

The bike has done few miles since the rebuild, and the person I bought it from was a Norton enthusiast who had owned multiple Commandos and was very knowledgable about the state of his bike and had done plenty of work on it himself. Based on the receipts, the previous owner, who commissioned the rebuild, imported it from the UK to Germany and then on to the US, was much the same.

Not saying that's any guarantee that everything's fine or that I should trust some unknown mechanic from 20 years ago. But I would primarily be stripping it down, verifying things look OK, addressing any "time bomb" issues and then putting it back together and riding it. I want to get some miles on it and understand what it needs and what I want from it before putting it up on the lift for a couple months and breaking out the credit card. I am very much *not* looking for an excuse to crack into the engine and polish, blueprint, and upgrade it.