2012 pro scored pistons

[canj]

I guys, both pistons scored on my 2012 pro rmk 800 2 days ago and I need a little help finding the cause.

I installed an rk tek drop-in piston kit this summer. Sled was running great but I had air bubbles in my coolant bottle ever since. I pulled the head off to change the o-rings last weekend and got out for a ride on sunday. Problem not solved but no other issue.

Got out for a ride on wednesday on a really hot day (minus 1 celcius) and 10 minutes later I was stopped with a burned down engine... It happend on a long river pull at 3/4 throttle. engine temp was good, fluctuating depending on the snow conditions. No light came on. I don't run with the ethanol plug and never had issue before.

pto side piston is scored all around with a grey top. mag side piston did not had time to completely burn but it has some marks on the cylinder on the intake side with a grey piston top too. There is some cylinder plating missing on the pto side.

Since this engine has always been reliable before the pistons change, I assume that I made an error or that something went wrong in the process of changing the pistons.

Any idea on what went wrong?

 

[o2bncamo]

Drop in kit? Was it just the replacement pistons, or pistons and head? Running a fuel controller? Pic of the pistons would help too. Both sides and the top.

 

[canj]

just the replacement pistons. No fuel controller. I took some pics of the top of the pistons and the cylinder walls. I'll take some pics of the pistons tonight.

https://www.dropbox.com/sh/q3y0gu0cxkuifxi/AAB71t-j_fx5SWXzDtObXQUDa?dl=0

 

[pulltype_polaris]

Was it just the ten minute ride that you had on the sled since install?

 

[canj]

no the pistons have been changed this summer and I ride every week end since the holidays...

 

[pulltype_polaris]

After replacing my pistons this fall I was pretty careful tracking my oil consumption. Before I opened up my motor I was burning about 70:1 but after it was up around 90:1. I did have the throttle bodies off and checked/replaced reeds though. But at any rate I was using less oil. I think there is enough slop in the bolt holes to throw off oil pump adjustment. Turned adjuster in 2 turns and I'm about 60:1 now. Your pistons I'd guess are oil starved. Especially since the intake port on the one is scored. Fuel washed what oil was there off.

 

[canj]

I'll take a look tonight...

 

[canj]

pics of the pistons added. I've notice that the pto piston is not scored all around as I thought : there's a corner of the exhaust port that's intact.

 

[roni87]

Is there oil in the line going from the tank down to the pump? Had very similar experience this wknd but blaming it on a oil cap not venting...oil in my tank but oil line was full of air when I brought it back home. Also made a swish sound when I opneed the cap the next day...

 

[mark]

scored

No carbon on the top of the pistons means a lean condition. Did you replace crank seals last summer?

 

[canj]

I changed the cylinder head o-ring the night before the "incident" and the wash was perfect on both pistons, so if it was not running lean since the pistons change.

I rebuild it friday and rode it yesterday and everything seems good. So crank seal must be ok. I'll test it just to be sure tonight and I'll inspect the wash...

I really suspect an air leak in the base gasket. That would explain the air in the coolant as well. Did not had problem with the coolant yesterday btw...

thanks for the help guys

 

[canj]

I tested the crank seal this moring and it is good.

 

[Turboegt]

Were these the Wisecos?

I had a very similar incident.

Mine made it 150ish miles. How many did yours?