2012 Pro seized before 700 miles.

[Leftys]

If Detonation is causing Lower Rod Bearings to go out these days than I am missing something. I have seen many pistons with holes melted right through them. Some big some small. This creates serious heat and I have not seen a Lower Rod bearing failure do to this. Back in the days of the XCR, XLT, Ultra, and earlier 700 RMK's burning pistons due to Detonation or Pre-Ignition was very common. I would like some solid proof or something that makes sense to how that can happen. What has changed to make these engines have Rod failures due to Detonation.

 

[hudini]

The only thing I can think of is that the explosion at the wrong time, (pre-detonation) sends vibrations or stress down the rod at wrong angle, and this causes unwanted loading on the bearing? Maybe even vibration to the bearings?

I don't even know if I'm explaining my thought well or even if its possible, but it's the idea that came to mind when wondering how DET could cause these failures.

 

[Leftys]

What you said makes sense, but it just seems strange that all of the Top Ends I have rebuilt due to Detonation with no Lower Rod Bearing failures and most of the dinasours still running. What is different now?

 

[BigMan]

I'm curious if it could be the bearings themselves. Is Polaris installing premium grade bearings in these things or some cheap knockoff from China? Quality of parts alone can sometimes make all the difference.

 

[TRS]

I'll bet its a MAPE crank.

 

[mountaincat 800]

It is a type 1 crank. Whatever that means. But whichever one it is I'm sure the bearings spec out the same.

 

[kiliki]

knock sensors stopped working on the cfi? that's a lot of them then.

 

[TRS]

It is a type 1 crank. Whatever that means. But whichever one it is I'm sure the bearings spec out the same.

The rods are very different in design. The MAPE rod design limits oil to the big end compared to the Fuji rod.
If you have each rod available for comparison, you will see the difference.

 

[bajah2x]

Its your oil cap not venting,its almost always the mag side lower rod that goes first..