2012 polaris pro Piston Failure need help

[Dingus]

Delete

 

[moto5151]

Look at the top of the piston. The edge shows the ring from the top. It didn't break off, it melted away. Ring materials are different then the piston, thus the reason those are still intact. The liquefied piston material poured down the cylinder. That caused the scuffs and deep scratches. But the way the skirt has a clean cut, baffles me.
I've never seen a piston go black when it melts. I've seen them go white, in the center. But that usually shows up with a small hole in the center where the plug is located. Lack of oil? Check your oil pump?

 

[Dingus]

Delete

 

[cdnredneck_t3]

How many miles on sled? It could be that the bad pistons bit you, could have went lean or it could have done something else. I would let the guys at Boost It give you a diagnosis if they are willing.

I think you are on the right page by deciding to pull the bottom end. If debris made it in the crank better safe than sorry. Also have a good look at the cylinder, any damage and it needs to be re-nikasiled. They can't usually be repaired by honing.

 

[NM]

Before this thread gets too sideways. My opinion is that if people are going to ride at this elevation they have to call us and ask us what fuel and boost is recommended.
We have had quite a few people riding the last week and not be person called us to ask what we recommend and most people are having issues hitting Det, over revving, etc.
We set these sleds up for the mountains and give our customers fuel and boost guidelines for the mountains.

I encourage anyone that owns a turbo kit on an sled to ask the Turbo kit manufacturer what fuel and boost to run at this elevation. The air pressure and ambient air temp difference from here to the mountains is night and day difference.

Too ride around here, turbo two stroke sleds should run 100% Race or Av fuel.

The other issue around here when it's 15-18 below is that the Thermostat is constantly opening and closing and the Pros do not have a bypass circuit to keep head and cylinder temps consistent. This can promote a cold seize situation and this would be evident in a 4 corner skid melt down.

I think Dingus has to write this off as a hard lesson learned and 9 lbs boost at 2700 ft with half race gas is not going to cut it. Especially at -18 degC and stock compression.
i personally have at least 25000 Kms seat time on turbo sleds and have never blown an engine.

 

[WesG]

I have a piston that looks just like that one. Not enough octane. Similar scenario, A/F looks good, Coolant temps good, piston and turbo bad. LOL. Det sensor kicked in but the damage was done. Pro's like octane with boost. Do not skimp on octane with these units. Save yourself the wrench time and headaches. 7/8 lbs is half and half and anything over 8 is full race if running stock compression and timing. JMHO

Edit- This is for lower elevation riding 3000-6000 ft.