Crank bearing failures

[Turts]

Ok, another buddy had his 850t ch!t out crank bearings. How common is this? What’s causing it?
His made it to 2800kms.


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[Lem Lamb]

Most likely the out put shaft side would be my guess...

String from a belt causing the seal too fail is 1 of the 27 reasons why it happens...

Too many causes too list...

Hopefully the case halfs and crank are salvageable...

 

[ABMax24]

Let me guess, lower rod bearing?

Auxillary injectors washing the oil out of the bearing, and of course the highest fuel flow through those injectors occurs at max boost, full load, and max rpm. Just exactly when you want oil starvation to occur.

Same deal as the Polaris 800 when it had an aftermarket turbo installed a decade ago, except we could run oil in the fuel to help the issue. Can't do that on a direct injected ETEC.

The NA 850 can have this happen too, but they run less fuel through the auxillary injectors so failures are less common and usually happen with more miles on.

 

[mikeydoo]

Why can't you add some oil to the tank? did it for years on my areo charged xm.

 

[JMCX]

It's not from lack of oil injection. Those things are thirsty. The auxiliary injector wash theory is plausible. Was there not a passage from the main to rod bearing similar to automotive? Why not premix a little? Sure, most of the time it's wasted by the direct injection but if it saves a crank. Especially out of warranty.

 

[ABMax24]

It's not from lack of oil injection. Those things are thirsty. The auxiliary injector wash theory is plausible. Was there not a passage from the main to rod bearing similar to automotive? Why not premix a little? Sure, most of the time it's wasted by the direct injection but if it saves a crank. Especially out of warranty.

Yup, that passage should have solved it. But the number of crank failures suggests otherwise. Issue is 95% so far have been warranty, so the engine doesn't get opened up at the dealer for inspection to verify this for certain.

ETECs are not supposed to run fuel in the oil, messes with the injectors or something.

 

[mikeydoo]

It may not be approved but it still works. I vented a 800 block at about 1000km. After that ran oil in the fuel for a calculated total of 20:1 with injecton and went 8000km on the next one. This was 2 generations of sled ago so I may be talking out of my ass lol.