what will do this piston scoring with rktec drop in pistons

purepolaris600 · Nov 23, 2014

I installed new rktec drop in replacement pistons last year, only 500 miles on pistons, I just pulled compression and it was at 93 lbs in both cylenders, spray a little oil in up to 120 lbs, so I pulled head and monoblock off and the cylenders are scored bad on intake side and so are the pistons, the intake side of the pistons wore into the rings making the rings stick, and made a sharp edge on top of piston, any body have this trouble or what could cause this, hade new monoblock put on last year at time of new pistons t

hanks

Danbot · Nov 23, 2014

Was the ring end gap set at instal? What was the gap?

purepolaris600 · Nov 23, 2014

gap

yes ring gap was checked and set at 19 tho, rktec spec is between 18-20 tho, thanks would it be do to lake of oil, almost seams like the piston was rocking in the cylinder.

Danbot · Nov 23, 2014

I'm no expert, and I'm sure someone with more knowledge than me will soon reply but here's what I see:
If possible post some clearer more detailed pictures. Head domes, top of pistons, intake side, exhaust side, skirt edges, cylinder walls.

The piston wash looks reasonable on the one top shown, no signs of melted aluminum. Thermal / lean condition meltdowns usually show melting and also include or are limited to this kind of damage on the exhaust side.

Lack of lube(snow ingestion, oil injection failure, etc), incorrect piston to cylinder clearance, tight ring gap would be my suspicions with the pics / info available.

RHODESIE · Nov 23, 2014

are they both like that? need the exact same pics that are not so blurry.

slash · Nov 23, 2014

Air box is sealed so no belt dust got in, hmm oiler turned to the correct setting no air bubbles ,had the hood on so no snow got into the intake . Looks like dirt or snow or something got into the cyl .

Norway · Nov 23, 2014

Clear pics are a must. And one showing the crown kinda close.

gman086 · Nov 23, 2014

Water (rain?) or snow ingestion. Did you wash the sled then run her?

Have FUN!

G

snowmobiler · Nov 23, 2014

a pack of mice made up a crib in your airbox

Sheetmetalfab · Nov 23, 2014

Looks like normal rk tek pistons after 500 miles.

tinkerjohnson · Nov 23, 2014

Rkt

What year is your sled? Are you running a fuel controller? I have run lots of these kits all run very strong and the one is pushing 3,000 miles never a problem. but I always install a fuel controller and add a lot of fuel across the entire map. Piston wash looks ok now but how long has it been running this way. it may have plenty of fuel now that the rings are not sealed and not running at its potential

polarisperformance · Nov 23, 2014

Same thing

Same thing as you on rk tek drop in kit (450 mile), on both cylinder and on the intake side. Exhaust side of the piston was like new. I saw it after my engine seized

Sheetmetalfab · Nov 23, 2014

Seriously though.

Looks like snow ingestion.

purepolaris600 · Nov 23, 2014

gap

Ok i will try to get better pictures also should metion was running turbo a 10 lbs with water to air, with plenty of fual on 100 ll, also no mice in airbox here sled has been sitting on stand in shop and all intake and exhoust taped off, both cylenders look the same and both pistons look identical, top and bottom of pistons have a sharp edge to it almost as if it rubbed harder on pistions on intake side, also did notice the top of the rods are blued. Hope this helps i am getting cylenders sent out tomarrow to get replated. I was thinking oil issues. I do mix my ave 100 to 1 oiler turned up 2 turns i did notice last year when i took my oilcap off it would suck air.

LoudHandle · Nov 23, 2014

From the most recent information; I would say insufficient oil quantity / oil starved. With the oil tank under suction, the oil pump can not overcome that to deliver enough oil to the engine regardless of how much you turn it up.

As much as I doubted the Phenomenon early on, I've come to believe that the vented cap does not function as designed on the PRO because of the mounting angle. You need to vent the tank, whether the Paaso Racing vent system or the Geo "Goretex" fix or any of the other methods listed in the oil cap / reservoir threads.

http://www.snowest.com/forum/showthread.php?t=374964

As much as I dislike Kelsey and his snake oil products and sales pitch, this was not due to the pistons, insufficient ring gap, etc. This would have happened regardless of what piston you had installed, and is likely the major cause of Polaris pistons getting a undeserved bad reputation. IMO

Fix the oiling issue and "run it like you stole it" with whatever slug you want to install.

mountainhorse · Nov 23, 2014

Looks to me like you have the piston ring upside down.

Wossner Rings

.

HAY FARMER · Nov 23, 2014

Rings are upside down..

snowmobiler · Nov 23, 2014

Mountainhorse wins

Bacon · Nov 23, 2014

purepolaris600 said:
Ok i will try to get better pictures also should metion was running turbo a 10 lbs with water to air, with plenty of fual on 100 ll, also no mice in airbox here sled has been sitting on stand in shop and all intake and exhoust taped off, both cylenders look the same and both pistons look identical, top and bottom of pistons have a sharp edge to it almost as if it rubbed harder on pistions on intake side, also did notice the top of the rods are blued. Hope this helps i am getting cylenders sent out tomarrow to get replated. I was thinking oil issues. I do mix my ave 100 to 1 oiler turned up 2 turns i did notice last year when i took my oilcap off it would suck air.

Lack of oil. I don't know how the polaris is but I would definatlty switch to pre mix. Especially wth a turbo. All that fuel that gets added doesn't have oil in it. Bluing of rods means heat and that is a sign of not enough oil.

Sage Crusher · Nov 23, 2014

mountainhorse said:
Looks to me like you have the piston ring upside down.

Wossner Rings

.

Great catch- and a Rookie mistake!! / Thats a lesson that alot will double check....

what will do this piston scoring with rktec drop in pistons

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