16' RMK 800 - Top End Re-Fresh?

[matchrocket]

Curious... how long are guys going on these motors before doing a top-end? Sled is non-boosted its whole life, runs great, static compression is the same as new as far as I can tell.

1700 Miles and ~115 hours.

Most of what I find are PRO Posts (1500 miles) or trail guys (5k+ miles)

 

[05rmksteve]

Best thing to do is a top end leak down test. My 16 past a compression test but failed the leak down test. Put a top end in it and now I have to add clutch weight. I gained 300 rpm with the new top end. Every sled is different some will go 5000+ on original top end some quite a bit less.

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[gdwrnch10]

Lost the engine on my 16 at about 2000 miles because a ring locater pin came out. Was running great up to that point.

 

[Indy_500]

My 16 was toast at 1800 miles. Ran ok for the most part with a minor bog here or there. Runs like a raped ape now.

 

[200smk]

Are you guys just dropping new Polaris pistons in? Any honing of any kind? Thanks

 

[Ultrasauras]

I would but a Fix/Durability kit in it I did the MTNTK one in my pro at 700 miles and it is still going strong at 2000 Miles I will be doing the same in my 2017.

 

[minus40]

Best thing to do is a top end leak down test. My 16 past a compression test but failed the leak down test. Put a top end in it and now I have to add clutch weight. I gained 300 rpm with the new top end. Every sled is different some will go 5000+ on original top end some quite a bit less.

Sent from my SM-G965U using Tapatalk

Interesting, 300 rpm is a big gain. Maybe i missed them, Would you mind sharing the compression and leak down numbers?

 

[05rmksteve]

Are you guys just dropping new Polaris pistons in? Any honing of any kind? Thanks

I did not hone the cylinder. I put a bmp durability kit in because I was already running a stage 2 and now with the piston kit I'm at a stage 3. If I was running a stock set up then I would have put stock pistons back in.

 

[05rmksteve]

Interesting, 300 rpm is a big gain. Maybe i missed them, Would you mind sharing the compression and leak down numbers?

My compression was around 120 each side and I had 10% leak down on the mag side. I installed a bikeman durability kit to up grade my stage 2 kit that I was running to a stage 3. So some of my rpm gain could be from the wossner pistons. But I'm also not dropping rpm in a long pull.

 

[Indy_500]

Are you guys just dropping new Polaris pistons in? Any honing of any kind? Thanks

I put SPI axys replacement pistons in with a light hone. I have 3 full days on them and it rips. I’m NOT a fan of forged pistons in a snowmobile so that doesn’t leave you with many options. OEM is the best option imo but they are pricey.

 

[Sheetmetalfab]

I put SPI axys replacement pistons in with a light hone. I have 3 full days on them and it rips. I’m NOT a fan of forged pistons in a snowmobile so that doesn’t leave you with many options. OEM is the best option imo but they are pricey.

Fyi.
2015 pro pistons are slightly cheaper than axys pistons and the toughest pistons available.

 

[200smk]

Fyi.
2015 pro pistons are slightly cheaper than axys pistons and the toughest pistons available.

Good info.....Thanks. I have a '16 that's getting near 2000 miles.....60-70% trail/flatland.....so thinking the 3000 miles mark would be fine to freshen it up (unless I start to lose power before that).

 

[AdrenalineAddict]

I would recommend that if you are out of warranty to replace those +100 hr. pistons as soon as possible. I have had 8 Polaris 800 twins go down because of the ring locating pin falling out between 98 and 112 hours since 2012. My sled gets ridden extremely hard (long uphill steep pulls, just for reference), hopefully others will chime in on sleds seeing a fair amount of trail miles. If I didn't have warranty they would be replaced at 85-90 hours.

 

[iluv2fly]

I put SPI axys replacement pistons in with a light hone. I have 3 full days on them and it rips. I’m NOT a fan of forged pistons in a snowmobile so that doesn’t leave you with many options. OEM is the best option imo but they are pricey.

)
I use to think the same thing on forged pistons but I have now installed the mtntk fix it kit in my last 3 polaris 800 sleds and they have all been rock reliable with zero issues. I think their pistons are much better than the stock polaris ones. My 16 axys has the mtntk kit, 100 gram lighter pistons, with the mtntk turbo and it runs like a dream. 2000 miles and going strong.

 

[St. Hellens rider]

Had 2600 miles on my 17 le. Compression was good. Running 11lbs boost since 300 miles and then this. Lost rod bearing and the bottom case.