Uh-oh!

Carl H · Jul 22, 2023

It sure looks like melted "Babbit" (for lack of a better word) to me. I use my own terms sometimes = Slang.

kommando · Jul 22, 2023

There is no Babbit used in Commando engines, the two choices for the shell bearings are aluminium/tin bimetallic or leaded/bronze with overlay plating trimetallic including factory fit. Babbit is for much lower output engines and with its high lead content has a very low melting point, so in no oil situations it will melt and ooze out from the journal. The alloy used in the con-rod is not far off aluminium/tin, in fact Briggs and Stratton make some of their con-rods from aluminium/tin and run them direct of the steel crank journal.

Tornado · Jul 22, 2023

Could a plugged up sludge trap be a candidate cause?

Carl H · Jul 22, 2023

kommando said:
There is no Babbit used in Commando engines, the two choices for the shell bearings are aluminium/tin bimetallic or leaded/bronze with overlay plating trimetallic including factory fit. Babbit is for much lower output engines and with its high lead content has a very low melting point, so in no oil situations it will melt and ooze out from the journal. The alloy used in the con-rod is not far off aluminium/tin, in fact Briggs and Stratton make some of their con-rods from aluminium/tin and run them direct of the steel crank journal.

IT still look like melted babbit or lead or aluminum , No kidding Norton uses shells. You know what slang means?

Larry S · Jul 23, 2023

Drained the oil and here are the remains after disposing the oil. Lots of metal, not ideal. Kept on with the disassembly and stopped after pulling the primary cover. Will continue on as time permits. Noticed the rod is cracked in at least two places.

Lineslinger · Jul 24, 2023

Is your crank end play/side to side movement within spec?

concours · Jul 24, 2023

Larry, you were SECONDS away from destroyed cases.
Again, good call to shut it down.

kommando · Jul 24, 2023

My guess is oil starvation at that journal, shells seized and welded to journal and then the shells spun inside the conrod. The shells ate into the alloy top of the conrod a lot more than they did to the steel bottom, the 2 joints would act like a saw blade. Hence the alloy shavings either side and the piston lower on the bad side and by more than just the thickness of the shells.

baz · Jul 24, 2023

kommando said:
My guess is oil starvation at that journal, shells seized and welded to journal and then the shells spun inside the conrod. The shells ate into the alloy top of the conrod a lot more than they did to the steel bottom, the 2 joints would act like a saw blade. Hence the alloy shavings either side and the piston lower on the bad side and by more than just the thickness of the shells.

I reckon you are on the money there
That way it'd be possible to eat that amount of Conrod in a few seconds

Tornado · Jul 24, 2023

But oil starvation due to what cause. He had oil. Did pump fail and this was first to failure point? More likely a blockage in passageway or sludge trap restriction.

kommando · Jul 24, 2023

Tornado said:
Did pump fail and this was first to failure point?

We need to wait until we see more pics, I am just going on the pics so far. More pics may show my guess is completely wrong but it does explain the piston drop and the valve also hitting the piston. The valve could be from the steel side of the conrod being worn away by the spinning shells, does not need much to start hitting a valve but the wear would be less than on the alloy side. The shell tabs will likely be flattened by the spinning but they will still have contributed to the wear. Its the crush/overstand of a shell bearing that stops it from spinning not the tabs. The tabs sole purpose is to make sure the shells are fitted the right way round and central.

acotrel · Jul 24, 2023

Just pull it apart and fix it. Each conrod is only held on by two bolts. When I ride a motorcycle, if the motor even misses once, I stop and fix it. That way the problems are usually small. Continuing to ride if the motor rattles is stupidiity.

possm · Jul 24, 2023

Larry are you running a anti wet sumping valve in your oil line?

CanukNortonNut · Jul 24, 2023

possm said:
Larry are you running a anti wet sumping valve in your oil line?

good question. But it is a MkIII

Larry S · Jul 24, 2023

Fast Eddie said:
Larry, do you wear earplugs and / or listen to music when riding (serious question BTW)?

I don’t wear earplugs and/or listen to music when riding. I am practically deaf in my right ear and have trouble hearing in my left. Because I only hear in mono and not stereo, I can’t even tell where the sounds are even coming from. That is if I hear anything at all.

Larry S · Jul 24, 2023

possm said:
Larry are you running a anti wet sumping valve in your oil line?

No I am not. I do have a pcv reed valve installed though.

Larry S · Jul 24, 2023

Tornado said:
But oil starvation due to what cause. He had oil. Did pump fail and this was first to failure point? More likely a blockage in passageway or sludge trap restriction.

When I pulled the head the rockers all had oil so my guess is the pump is/was working. I’m sure it’s contaminated with debris now so will need stripped and cleaned if not replaced.

Fast Eddie · Jul 24, 2023

Larry S said:
I don’t wear earplugs and/or listen to music when riding. I am practically deaf in my right ear and have trouble hearing in my left. Because I only hear in mono and not stereo, I can’t even tell where the sounds are even coming from. That is if I hear anything at all.

That’s a bugger.

An oil pressure gauge would be wise in that case if you don’t already have one. But IMHO they are mainly good for understand trends, a catastrophic failure can easily still happen before you’ve glanced at the gauge. Well, it did with me once !

Plus, and this might be controversial for some: perhaps experiment having the ISO’s set a little tighter, just enough so they transmit a little more feeling from the engine, that way you may detect abnormal vibes, and if coupled with an oil pressure gauge, may give you more of an early warning ?

Shelby-Right · Jul 25, 2023

Fast Eddie said:
That’s a bugger. An oil pressure gauge would be wise in that case if you don’t already have one. But IMHO they are mainly good for understand trends, a catastrophic failure can easily still happen before you’ve glanced at the gauge. Well, it did with me once !

I know most on here say they are distraction , but I don't think it's much different to looking at the speedo or rev counter , it is good for a sudden change , like a blown seal and sudden loss of pressure .

L.A.B. · Jul 25, 2023

possm said:
Larry are you running a anti wet sumping valve in your oil line?

Larry S said:
No I am not. I do have a pcv reed valve installed though.

Larry, is the Mk3 anti-drain plunger (circled) fitted because none of your rebuild thread pictures shows the plunger in position inside the Mk3 timing cover although of course it could've been fitted but didn't get into any of the pictures?
Without the plunger, the relief hole that vents the plunger cavity would be an open 'hole' in the timing cover oil feed gallery and although small in diameter, once the oil thinned out there would perhaps be a significant loss of feed/pressure without the plunger.

Uh-oh!

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