Blown m8 motor, broken skirts PTO side

[bartonls]

Last winter my m8 motor decided to go clankity clank and leave me stranded in about 3 feet of fresh powder 10 miles from the trailer.

After I got it home I dug into it and I was shocked, but impressed. I had never seen this happen before.

I just started the rebuild process because I had a bunch of projects to get to first.

Before I rebuild the whole thing, I would like to hear some ideas on why it happened in the first place.

Concerns:

1) I am not sure if it overheated (I have dual Koso EGT gauges and coolant temp, BUT.... the gauge shorted out and would not read anything the day before after a quick power-wash) Maybe it was taking power from fuel pump? I have never had a problem with high coolant temps, and EGTs only get too high if you cruise on the trail without varying the throttle.

2) The Mag side head and plug has never looked like this (What is with the thick black glaze?)

3) Could a bad PTO seal cause this? Bad injector? Stuck power valve?

4) I do not have the stock m8 gauges so I am not sure if it threw any codes. The ECU was tuned by Speedwerx and the arctic cat race team.

5) Anyone want to buy a rolling chassis (2008 sno pro 600 with 158" track, m8 skid, custom tunnel, etc.) Kidding, kind of.

Here are some pictures for your enjoyment.

Thanks in advance for any ideas before the rebuild!

 

[Anylizer]

Typically see this kind of failure with excessive mileage. How many on this engine?
Also if you take a close look at the other piston, you may see cracks starting in the same locations on the sides under the pin.

 

[mmsports]

Ice snow

Is possible it in-gusted a peace of ice from air box. That will have that affect.

Its from snow melting then freezing inside box.

 

[bartonls]

Thank you for the reply, this could definitely be the case, as I am not sure how many miles are on the motor. I had the motor out because I was replacing the water pump seal and I had all the parts for a top end rebuild, but the compression was great... so I put motor back in the sled. The second day out on a weekend trip it gave up. Lesson learned on this one.

Typically see this kind of failure with excessive mileage. How many on this engine?
Also if you take a close look at the other piston, you may see cracks starting in the same locations on the sides under the pin.

 

[bartonls]

Is possible it in-gusted a peace of ice from air box. That will have that affect.

Its from snow melting then freezing inside box.

Thank you for the reply! This is also a possibility. The air box is custom on this sled, and I just glued some frogzskin material over the stock sno pro 600 nose cone. I noticed a 2" rip in one of the screens during dissasembly. The box definitely got some snow in it, which probably melted and then turned to ice over night. I also don't have the coolant running to the throttle bodies because there isn't room. Looks like I'll be buying the updated 2010 snopro nose cone and filter just to be sure!

 

[kiliki]

the ice hits the piston top and cools it so you end up with one "cold piston" not to mention the air fuel mix up. congrats some guys can break the anvil in the sand box.

 

[BD-Xtreme]

The scoring on the piston skirts front and rear could definitely be from moisture ingestion of some sort. This would typically give the pistons more clearance. Notice how polished looking the very bottom of the good piston is? Since that area is very narrow that is showing signs of too much clearance, which could cause the skirts to have too much force on them and break. Or simply just too many miles on the pistons and someone else already mentioned may have caused the failure.

I have brand new take out pistons and heads in stock. The ones I have are the HO ones, but you are still fine to run them.

Is the motor modified? Ported? A larger exhaust port can make the pistons wear out faster too.

http://www.bd-xtreme.com/index.php?id_product=67&controller=product

 

[bartonls]

The scoring on the piston skirts front and rear could definitely be from moisture ingestion of some sort. This would typically give the pistons more clearance. Notice how polished looking the very bottom of the good piston is? Since that area is very narrow that is showing signs of too much clearance, which could cause the skirts to have too much force on them and break. Or simply just too many miles on the pistons and someone else already mentioned may have caused the failure.

I have brand new take out pistons and heads in stock. The ones I have are the HO ones, but you are still fine to run them.

Is the motor modified? Ported? A larger exhaust port can make the pistons wear out faster too.

http://www.bd-xtreme.com/index.php?id_product=67&controller=product

Thanks for the reply. I already have all the parts I need, just waiting on some crank seals, crank bearings, oil and water pump shaft seals, and getting the cylinders back before I can start on the rebuild but thanks.

Ya it was ported by speedwerx. The head is fine, it looks dinged in the picture but no damage. I also have a high compression head that I can use as well after I get a fuel controller.