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2012 800 engine

Discussion in 'RMK' started by Crambo, Nov 26, 2019.

  1. Crambo

    Crambo New Member

    Messages:
    1
    Location:
    Central Point Or
    Country:
    USA
    Years Snowmobiling:
    40+
    Snowmobile:
    12 Polaris 800 RMK PRO
    Yesterday I purchased a 2012 800 RMK Pro. 2900 miles. I have heard that around 3000 mile the pistons need replaced. Mostly what I read is he said accounts. On occasion there seems to be verified problems. So what to do what to do. Apparently there is no way to determine the condition of pistons until they let go. It seems to me with the 10's of 1,000's of machines sold there would be more verifiable piston problems. Did a rare event case an avalanche ? How about hearing from riders that have 3000 plus miles with no problems.
    Thanks for all your help.
     
  2.  

  3. George A Twitchell

    George A Twitchell Member

    Messages:
    54
    Location:
    Laramie, Wyoming
    Country:
    USA
    Years Snowmobiling:
    48 years
    Snowmobile:
    Polaris 2011 PRO 800-163
    I have had quite a bit of experience with the PRO series from MY11 to MY15 and still have a 2012 in our stable here and as I went on from my MY11 I found out that there is only two brands of pistons to put in when you are going to do the top end and the "Fix Kit" is not necessary. After doing several fix kits with very poor luck and talking with Indy Dan several times the conclusion I came to was just what Dan said---- Use stock Polaris pistons (use the 2015) and do not hone the cylinders unless you get Dan to do his "plateau hone process". Look at the cylinders and if they are nice and shiney, wipe them with scotch-brite green, wash with soap and water and assemble with 2 stroke oil break in and ride on.. I did find also that SPI stock pistons are good replacement and I used them on the last 2 top end rebuilds and they are still running strong after 4 years and each one of them has lots of miles. and with good compression. I sold my 2011 and the owner is still happy with it and the 2012 is still in the trailer and is ridden often. Just my experiences and of course my opinions here. Now have 2- 2018 800 -163 AXYS in our stable, riding stock with gear down from 2015 PRO---- GREAT RIDES!! I never run out of power or performance, if i get balled up , it is always a lack of talent/skill!
    gtwitch in wyoming
     
  4. Maydaze

    Maydaze New Member

    Messages:
    19
    Location:
    Hagaman, New York
    Country:
    USA
    Years Snowmobiling:
    48
    Snowmobile:
    Polaris Assault 800
    Well, I can tell you from experience that the thin skirt 12' cylinder is the issue. Check your cylinder skirt for cracks and have the cylinder measured, top to bottom. Mine cracked at 1200 miles. I found it while doing preventative maintenance and replacing the pistons. Replaced with an Indy Dan reinforced cylinder and the skirt broke off at 3400 miles taking the whole engine out. I had the SPI pistons with the oil grooves in it at that time also. Now, I have a complete 15' engine in it. We'll see how long this one last.
     
  5. Mike-DRH

    Mike-DRH Member

    Messages:
    36
    Location:
    Hastings
    Country:
    USA
    Years Snowmobiling:
    40
    Snowmobile:
    2019 Polaris Rush 800
    Pistons very rarely (maybe never) just plain wearout. In almost every (maybe all) piston failure(s) it's caused by something other than wear on the piston.

    All of the big 4 have had problems in the past with parts of the engines, including pistons. They were widely publicized, mostly by consumers, and they fixed it.

    I'm always a little leary when I hear someone say "I have three buddies and they all had the same problem". Some of this a little like "fish stories" and may be jazzed up a bit and if it is true don't ride with those three buddies they are extremely unlucky people.
     
  6. Maydaze

    Maydaze New Member

    Messages:
    19
    Location:
    Hagaman, New York
    Country:
    USA
    Years Snowmobiling:
    48
    Snowmobile:
    Polaris Assault 800
    The problem with the pistons on the 12' and some other years is that they were losing shape. The skirts were 'collapsing', coming in, until they finally broke or from rocking to much in the cylinder, break the cylinder skirt. Pistons in a 4 stroke are totally different than 2 stroke pistons. 2 stroke pistons have more of a tendency to get scratched, lose shape, melt down. They still might go up and down, but that does not mean that they are good. I use Forged pistons when I need to rebuild an engine and have had nothing but good luck with them over the last 40 years in liquid cooled and fan cooled engines. Some people do not care for them, that's fine. Polaris had great luck when their pistons when they were made by Asso. Then they changed. They finally have a good quality factory piston, but it took them several attempts.
     
  7. Polaris man

    Polaris man New Member

    Messages:
    6
    Location:
    Prince Edward Island
    Country:
    Canada
    Years Snowmobiling:
    40
    Snowmobile:
    2016 Polaris Assault
    I have 7500 miles on my 2016 800 Assault with 130 and 135 pounds compression. The engine is still all original and working good. The oil pump was turned up sense new. What are some opinions on when to rebuilt top end and with what pistons should i use. I only put an average of 1500 miles an year.
     

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