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Micha
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While checking the crankshaft and its front bearing before assembly into the engine, I saw some marks on the crankshaft front shoulder, where that main bearing should sit.
I decided nevertheless to mount the crank into the heated engine case and during the front bearing cover assembly I applied a bit of Loctite bearing-surface adhesive to the bearing. When everything was assembled and still hot, wet and liquid, I had a two-millimeter front-rear crankshaft play. After setting and drying, there is no play at all (of course).
I remember that the bearing cover with bearing inside got onto the crank without heating it, so there is a bit of wear on that shaft.
I would like to know if someone over here knows the diameter of the crankshaft where that bearing should sit.
What do you think in total? Will it last (as it did until I disassembled the bike) or do I have to go through a chromium Filling on that shaft?
Thank you all.
Michael

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

Micha
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Correction: the adhesive was

Correction: the adhesive was not a Loctite item.
It is a Swiss made ERGO type 4452. I have checked on the web and it states:
Flash point: > 100°C
I doubt the engine oil could reach that heat, even in a slow summer ride, but then again - I am not sure.

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

Jim D 5112
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Flash Point

I would think that the flash point is only relevant when the adhesive is in a liquid state before that it has set up and cured.

Micha
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Thanks. I talked to a friend

Thanks.
I talked to a friend who deals with aviation parts design. He told me that every axis that is inside a bearing has such an allowable tolerance so it can theoretically move inside the bearing. The bearing never grabs the axis in an absolute way.
All that worries me is what happens if I assemble the bearing on the crankshaft when the last one is worn, that is, below the permissible diameter setting.
He calmed me down and said that both the glue would do its thing and the crank’s expansion as it warmed up and that everything was fine... He thinks that the crank axis will never be able to turn inside the bearing around itself and “you are not dealing here with a race engine”.

What do you guys think?

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

malmac
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Toowoomba, Australia
Joined: 06/29/2014
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A point of view

Unfortunately I am unable to add good news to your situation.

My son has an R60, 1968 build. He had a worn rear journal on his crankshaft. I tried Loctite 680 and reassembled the engine.
The bike is not a race bike but the 680 did not hold, so eventually we secured an alternative crankshaft and that has fixed the problem.

The reality seems to be that the crankcase expands more quickly and perhaps overall more than the steel crankshaft.
This expansion means that the rear bearing is given the capacity to move within the rear bearing carrier.
The front bearing is locked into it's bearing carrier, so the front of the crankshaft should remain in position and the rear bearing adjust for the expansion of the crankcase. I hope that makes sense.

The implications I see for your engine is that the expansion is trying to pull the crankshaft rearwards out of your front bearing and it is only the bearing mounting glue that will be holding it.

Will it hold it all OK? Well I don't know, but I do know that loctite 680 was not able to secure the rear bearing onto the rear journal of my son's bike.

Sorry I was not able to give you better news.

Mal

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mal - R69s
Toowoomba- Australia

Micha
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Thank you for this info,

Thank you for this info, Mal.
How did you find out that the loctite didn't last?
Was there a particular noise sound?
Was there mechanical damage?
Did the motorcycle get stuck?

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

malmac
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Toowoomba, Australia
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Subsequent work

We eventually decided that it was time to restore the engine more fully.

When it came time to remove the rear bearing from the crank journal, it was able to be taken off without resistance.
The bearing had been freely spinning on the crankshaft journal.
We replaced the crankshaft with a new one and I have yet to get the old crankshaft rebuilt.

In your case the problem of failure would possibly be more accute as the front bearing is meant to hold the crankshaft in place end for end.
I fear that what would happen is that the front timing gear would then be relied upon to maintain the crankshaft roughly in position.

I think that could cause more serious issues.

Just my opinion, others would have more experience than I do.

All the best

mal

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mal - R69s
Toowoomba- Australia

malmac
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Toowoomba, Australia
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I didnt do this to prove a point

Today I pulled the crank out of our R69s engine.

The rear bearing literally fell off the rear journal.
I haven't measured the lack of interferance fit, but in the photo you can clearly see the residue of the liquid bearing mount that failed admirably.

This engine has probably done 10,000km since the last owner rebuilt it.
I am allowing that 8,000kms of that travel was by him.

The slingers were virtually empty which adds weight to my assumption.
In short I don't think bearing mount liquids are the answer.

Mal

  • mal_0676.jpg
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mal - R69s
Toowoomba- Australia

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