Piston question

RobertTrivanovic · Sep 27, 2014

So I pulled my y pipe and looked inside my engine and found that one of my pistons was scratched up nicely. There is one deep scratch in it which concerns me, and also it looks like the coating on the side of the piston was flaking off. I put these pistons in last season and the sled didn't miss a beat all season, if I didn't look inside I never would of even thought there was an issue. Anyone know what could of caused this? Im pulling the cylinders in the next few days to take a look at them. I'll attach a picture.

Also the sled ran rich all season and the top of the pistons look completely fine, no signs of det on the top anyways, not sure if this could be a sign if det?
Sled is also turboed

Ps. Aside from the one deep scratch it's not as bad as the picture makes it look.

RACINSTATION · Sep 27, 2014

This would depend on the other side of the piston. Based on the picture, I would say that you are running lean at one area or another of the powerband. The melting of the aluminum would lead me to believe this. The question will be if the intake side of the piston looks the same as the exhaust side.

This can be caused by too low of octane in your fuel selection, not enough in the mix ratio, or an airleak. Get some pics of the inside of the cylinders and the intake sides of the pistons for a full analysis.

RobertTrivanovic · Sep 30, 2014

The back is also scratched but not nearly as bad, if it was running lean why would it be only one cylinder?

RACINSTATION · Sep 30, 2014

I'm going to go out on a limb and guess that it was the PTO side?

RobertTrivanovic · Sep 30, 2014

Actually no the Mag side

RACINSTATION · Sep 30, 2014

What fuel controller are you running?

Usually the PTO side is the hotter side. You may have an airleak if it is the mag side.

If you have oil injection, make sure that the feed line is not kinked and is working correctly to that side. If you premix, make sure you are cross drilled (this is more for the crank than the cylinders).

I have seen sleds with the Boondocker controller and say the are running 5 on the trim, it is enough extra fuel to keep the PTO side happy and then you lose the mag side.

diggerdown · Sep 30, 2014

Check your fuel pressure, if it's a little low it will take one side out.

RobertTrivanovic · Sep 30, 2014

Im running a PCV and its the stock oil injection system. Ill check for kinks later, Im even more surprised by this because the PTO side injector was leaking a tiny bit so that side was getting even less fuel which makes this make even less sense to me.

Ill check fuel pressure once everything gettings rebuilt.

The other weird thing is the sled ran good 9 times out of 10 all season and the last day of the year was one of those good days.

If I had a air leak somewhere where would I be looking for it? Crank seals?

RACINSTATION · Sep 30, 2014

The air leak is usually in a reed boot or a crank seal. Are you running autotune? Do you have you map advanced so it is split between the cylinders?

RobertTrivanovic · Sep 30, 2014

No autotune and the cyclinders were both tuned the same no differences between the two.

At the beggining of the season one of my first few rides on the new pistons my sled shut off and I couldnt start it almost felt seized, 15 minutes later it fired up and I never had an issue after that. Is it possible something happened early on and the sled just ran like that all season and the issue disappeared? It have cracked and chipped reeds at the time and I had a boost leak so I was chasing so many things at once I thought it was just related to something like that and never worried about it after.

tjcatman · Oct 2, 2014

Pistons

First ride on new pistons? Did you heat-sink them? Often on new pistons you run them through a heat cycle and let the motor cool two or three times to let them sink to the cylinder walls. If you did not do this I'm betting that is your issue. Artic cat has such tight clearances in he motor this needs to be done every time new pistons are put in. I bought two new sleds in 2009 and the dealer failed to do this. 5 miles two seized sleds on the trail within 200' of each other. Let them cool 1/2 hr. before they would start and rode them out. Pistons on one side looked the same as yours. Hope this helps

madmax · Oct 2, 2014

What brand pistons did you put in? Your problem early last year sounds like you cold seized it and then broke it loose.

RobertTrivanovic · Oct 2, 2014

Yes it was the first ride if I remember. I did heat cycle them I believe it was twice in my garage and then loading the sled again would probably count as a third since I fully warmed it up.

Now that I think of it, its possible I had an air bubble in my coolant lines and thats what caused it?

I wish I could remember if I had to top up after the first ride or not.

And they were OEM pistons

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Piston question

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