Why do these Crank Mag Bearing cages crack?

[///M5]

So I pulled this crank to rebuild a motor, and noticed that the "Mag Bearing cage"? Is cracked.

This same thing happened to my 66V Crank, and in both cases the bearings are super smooth with no noise.

What's going on that's making these fall apart?

 

[modularjunk]

That looks like water intrusion damage to me. From what i see in the pics there is a lot pitting on the crank and the rust on the bearings i would say you are getting water in the motor.

 

[///M5]

That looks like water intrusion damage to me. From what i see in the pics there is a lot pitting on the crank and the rust on the bearings i would say you are getting water in the motor.

That pitting was from the timing cover leaking. The inside of the motor is clean, and the bearings roll really smooth with no noise.

What I want to know is why that ring in the mag bearing cracks. Does it happen to anyone else? I have 2 cranks that have good bearings and rods, but that cage is shot.

 

[BruceSki]

I have four or five crank cores on the shelf with the same problem.

 

[OCD Solutions]

@ScottS

 

[Freakrider]

I believe those are dust covers (black plastic) and not bearing cages just to clarify things on your question.

 

[kevbo]

I extend an oil passage in front of the bearing.

 

[Freakrider]

I extend an oil passage in front of the bearing.

Please explain this ? Thanks.

 

[BruceSki]

Looks like it holds the balls in place to me?

I only have one broken on right now

 

[///M5]

Looks like it holds the balls in place to me?

I only have one broken on right now

That's what I thought. So when this cracks or disintegrates, it makes them unusable right?

 

[BruceSki]

I wouldn't run one in my own ski. But I have pulled running skis apart with bearings that looked like that. They will last a while on a stock boat that doesn't turn super high RPMs.

 

[///M5]

I wouldn't run one in my own ski. But I have pulled running skis apart with bearings that looked like that. They will last a while on a stock boat that doesn't turn super high RPMs.

It looks like the bearings will bind up when they hit each other from not being retained. My 66V crank has the same problem, and I'm scared to run it that way.

If I didn't pull it apart to change crank seals, I would have never known.

For all I know it's common and not a problem, but common sense is telling me otherwise.

 

[///M5]

I extend an oil passage in front of the bearing.

Does this mean that it is caused by lack of lubrication on the mag bearing?

 

[Blue]

The black plastic does act as a cage to seperate the balls. Its hard to say why they fail and crack. Could be heat, lubrication problems or the crank moving forward and backward as the bearings wear. I see this every so often even on clean looking oem cranks.

Sent from my SAMSUNG-SM-N900A using Tapatalk

 

[///M5]

The black plastic does act as a cage to seperate the balls. Its hard to say why they fail and crack. Could be heat, lubrication problems or the crank moving forward and backward as the bearings wear. I see this every so often even on clean looking oem cranks.

Sent from my SAMSUNG-SM-N900A using Tapatalk

Thanks for the info,

So basically, if this cage is gone or starting to break up. The crank is no longer safe to run correct?

 

[Blue]

Correct. Replace the bearing or the crank.

Sent from my SAMSUNG-SM-N900A using Tapatalk

 

[kevbo]

Does this mean that it is caused by lack of lubrication on the mag bearing?

I never thought that it was adequately served by the stock oil passages. I extend the stock passage to assure the bearing hole is not covered and cut a channel to the front side with a 1/8" ball file.

 

[OCD Solutions]

We did a similar trick to the Skidoo triple 800's. They would prematurely fail the PTO bearing as well unless you extended the oil passage.

 

[snowxr]

Ethanol. Doesn't play well with some plastics and rubber parts.

 

[///M5]

I never thought that it was adequately served by the stock oil passages. I extend the stock passage to assure the bearing hole is not covered and cut a channel to the front side with a 1/8" ball file.

Please post up a photo of your case mod if you have one.