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Just my 2 cents.

Are you sure that the piston didn't seize first? That type of bearing failure looks like your crank is bent. When this happens, the balls no longer follow the grove in the inner race, but unstead try to climb out. I think the cage got pushed out because of this.

Looking at your crank, a split like that has to come from trying to peel the shaft from the lobe. This is common for a bent crank.

Just a thought - check your runout, its probably terrible.

A few points to check to determine if the root cause of failure was from the crank bent - or if the bearing failed first.

- Check the balls. do they look like there peeling? Do they all have this "peeling"?
- Do the balls look burnt?
- These 2 items would show a gradual bearing failure gone critical

On the other hand,
- Check if the balls look clean
- Are a few ball clean with pitted marks
-  Do some balls look good?

These thing would indicate that you had a forced failure of the bearing. They were running good and then started running out of thier groove in a helix patern.

Don't worry about using locktite. I instruct all my gearbox assemblers to do the same. - Helps elliminate creep and corrosion fretting on the outer race.
I don't think it will affect the heat disipation. After assembly there is barely a film a locktite.

Can you post a close up of the bearing?

Hope some of this is useful
 

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Limskii, nice picture.

You can tell alot from this pic. First off - you were right. That bearing is beyond allowable tolerences. When you lose the mirror look of the balls it is because they are getting rough. They get rough because they are loosing surface material. If you were to compare that ball in the picture to a new one using a powerfull microscope it would look like huge crators are forming. Another indication is the dark color of the groove in the inner race. This is because of the poor surface quality of the balls. If the balls were perfect, that surface would be mirror like.
Looking at this picture, it is defenetly not a failure due to the cage or cage material. The cage is damaged because the crank let go under load - forcing the balls the run out of their groove.
The bearings were installed properly because there is no indication of a shoulder forming on the inner race. If the bearing was cocked you would feel a ridge at the edge of the groove.

My guess is some type of cyclic stress on the crank, due to excessive axial/radial play in the bearing.

Just my 2 cents, hope some of this is usefull

Thanks for the picture, and I'm glad you don't need to line bore.

Good luck next season
 

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These are good facts that you mention ski-dood.I aggree the bearing did overheat I don't think anybody disagrees. Overheating causes bearing wear and failure. The wear on the balls and the inner race is definetly  from heat. But I don't think it comes from the lack of coolent contact or coolent efficiency.
When the balls become worn like the ones in this picture, it creates an increase in surface friction. This heat from friction has a much bigger impact than improper cooling. And is degenerative, which means that the more you run, the more heat is created, which means the more wear is created, which means the more heat is created and so on, and so on.

This wear is what I think cause the crank failure. Because eventually the looseness caused flexing in the crank.

Thats another good point on the outer race being compressed. This causes the balls the run harder/hotter and fail. But I don't believe that this type of application can cause this. You sound like your familiar on this type of failure probably because you work on split bearing cartridges that need to be shimmed, or on the taper roller bearings that you need to tighten up the locknut on the taper sleeve in order to achieve proper clearences. And we all know what happens when they are improperly installed. You run the equipment up to speed, measure the temp, and watch as the temp keeps climbing to critical.
But on the type of bases on sleds, I don't think it would be possible to compress the race enough. The only way I could see this happen is if the groove where the bearing sits in the housing was damaged and had a high spot or not properly cleaned. Then I could aggree that this could cause the bearing wear.
Using locktite only creates a film, the excess gets pushed out plus I don't think it has the strengh to compress the race.
As far as the locktite goes for heat transfer, it does not have the "R" value to insulate. So basically if the bearing is hot, the locktite is hot, so heat will still be removed.

Interesting theories, but in the end, we both may be wrong. These are just our 2 cents and don't actually have the bearing in front of us to study.

Just my opinion
 
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