2017 axys rmk top end

[seef158]

So the time has come to do the top end, pto side down. I'm leaning towards Indy specialties as he is local to me. Utah crankshaft has complete kit with cylinder and a " fix kit" spacer and sp1 pistons and they are about 500 cheaper than Indy dan. Anyone have any experience with Utah crank, and is there a benefit to the fix kit spacer on a 2017? Again leaning towards IS but figured I'd throw this out there. Thanks in advance. Also any input on root cause welcome. Mag side is in near perfect shape. I almost think bad plate job? Pretty lucky we didn't have to tow this out of the back country!

 

[sledhed]

Miles? Just redid my 2017 top end at 2100 miles and everything looked great... that does look kinda like a bad plate job... I would do IS top end, fix kits with spacers aren't needed in Axys HO motors from everything I have read, also read lots of horror stories with them blowing up at low miles...

 

[seef158]

Miles? Just redid my 2017 top end at 2100 miles and everything looked great... that does look kinda like a bad plate job... I would do IS top end, fix kits with spacers aren't needed in Axys HO motors from everything I have read, also read lots of horror stories with them blowing up at low miles...

Only 1200 miles on it. Thanks, I'm leaning towards IS. I'll probably put crank seals in it and have injectors tested and I SHOULD be good. I'd have sold as is and upgraded but I'm in process of a divorce so can't do chit!

 

[seef158]

This just has me confused too, mag side looks mint so thinking crank seal, injector or just bad plating. To me it doesn't appear to be a lean condition but I'm used to carbs. Not to mention I had RPM loss and still trail rode it 15 miles back, I'd think if lean it would have ended itself on that trail ride back.

 

[BeartoothBaron]

I wonder if it's a plating issue too. I'm doing my top end - due (I think) to a locating pin failure on the PTO side - basically, a ring moved and broke up and tore into the cylinder, mostly around the exhaust port. Outside of where the broken ring was scrubbing the cylinder wall though, there wasn't much damage to the plating. I don't see anything that would cause the damage to run all the way down the cylinder like you've got; maybe a lack of lubrication could cause that though. Anyway, mine caught me at an equally bad time. My motor's an IS long rod motor, and I contacted them, but they don't have OE pistons (I hear those are hard to find anywhere; I think it was SPI the offer as a substitute) and couldn't do anything for me as far as price (motor was well out of any warranty though).

Meanwhile, I had several guys recommend Wossner pistons. There have been several very knowledgeable sources who swear by only OE pistons, but the locating pin is a weak spot that keeps cropping up (usually on sleds that see long WOT runs), even on the 850. Forged pistons get dumped on for deforming and/or seizing, but I think there are two things behind that. First is that older forged pistons were 2618 aluminum allow, which could tolerate abuse better, but was less rigid and expanded a lot more than cast pistons. Then came 4032 alloy, which is what Wossners are; that adds silicone back to the mix (both standard cast and 4032 are around 12% silicone; 2618 is <1%). It keeps most of the strength of forged, but makes it more rigid and lowers the expansion rate. The downside is some of the brittleness of cast comes back with it. The second issue is cast is still best in terms of expansion rates. So, especially in a situation where you're offering a warranty to people whose idea of a warm-up is letting the engine run long enough get their gloves and goggles on, cast will have the least immediate failures. There are probably other causes of premature failure, but I'm pretty well convinced that most issues with forged pistons are from clearances too tight and/or lack of warm-up. So I'm giving Wossner's a try, but I will add leakdown checks and piston/cylinder inspections to my regular maintenance. I'm not sure I could have caught my problem in time, but I can't say I'd done a thorough check-over.

As mentioned, I do have a long rod setup, and I'm convinced that's the best on the Pro 800. It's a better choice than the "fix kit" taller pistons, but I don't remember the explanation that well, and can't say how much benefit the 800 HO gets. I think the long rod setup is something that could only help, but may not be worth the effort on the HO. The HO seems to need top end work almost as often as the Pro 800, but I don't hear of nearly as many bottom end failures.

 

[sledhed]

Locating pins coming loose were a known problem on the 17s for sure, not sure who told me that but I am pretty sure it is on the snowest forums somewhere too... IS says to use 2015 pistons as there is no benefit they can see in the newer $50 per piston more expensive ones... I ordered mine last summer knowing I wanted to do a top end as maintenance. I also used to be a fan of forged pistons, I think that is what was in my Carls 860 Dragon, I always let it get up to operating temp before riding... I am doing that now as well, just a good habit.

 

[BeartoothBaron]

TRS is the guy I've heard the most from about locating pin issues, but he's not the only one. Unless the Wossners have some kind of premature or catastrophic failure, or just don't last very long, I probably won't go back to OE. They're lighter (I weighed them; I think it was 65g less), cost half the price, and appear to be of equal manufacturing quality. I'm not sure how hard the OE pistons are to get right now, but they're the only ones I see being better quality than Wossner or Wiseco. The non-OE cast piston options seem to all be a copy of the OE piston, made in Taiwan. They're ok, it's just that personally, I think getting a piston from a top-tier manufacturer is worth more than sticking with cast on a sled that's going to see hard use.

 

[sledhed]

TRS is the guy I've heard the most from about locating pin issues, but he's not the only one. Unless the Wossners have some kind of premature or catastrophic failure, or just don't last very long, I probably won't go back to OE. They're lighter (I weighed them; I think it was 65g less), cost half the price, and appear to be of equal manufacturing quality. I'm not sure how hard the OE pistons are to get right now, but they're the only ones I see being better quality than Wossner or Wiseco. The non-OE cast piston options seem to all be a copy of the OE piston, made in Taiwan. They're ok, it's just that personally, I think getting a piston from a top-tier manufacturer is worth more than sticking with cast on a sled that's going to see hard use.

Indy Dan had done a post on different pistons and what he theorized as lifespans but I think that was a while ago, I thought the Wossners were too tight a clearance but I may be wrong...

 

[seef158]

At this point I've decided to pull the bottom end, put crank seals in and IS is putting all the parts aside for me and will test the injectors when I pick up the parts. They are local to me so that aided my decision. Hopefully there is something to his hg7 hone and the ride cool head to upgrade to the 2018 design that will help this thing last. It's gonna cost me a quarter of what I've already invested but new sleds are expensive. I want to keep this sled as a back up and maybe cut it down and put a 146 under it one day so it's more useful here in MN, then buy a newer one for mountain riding but that's gonna be a year out at least depending on how bad I get taken to the cleaners lol. Thanks for the replies guys

 

[flying frenchman]

I just picked up new OEM pistons
Man did I have fun getting them.
2015 pistons subs up to new style AXYS pistons with the grooves in them on the skirts.

 

[BeartoothBaron]

Indy Dan had done a post on different pistons and what he theorized as lifespans but I think that was a while ago, I thought the Wossners were too tight a clearance but I may be wrong...

This thread is one I've read through several times - https://www.snowest.com/forum/threads/polaris-800-owners-dont-replace-your-stock-pistons.433563/ Dan says all forged pistons fail his test, but it's not something I'd ever do with a sled I own (start with stone cold sled, let it warm to 70F, then immediately run it wide open for a mile). I mention the question of the warranty, and the test makes sense in that light, but I think most of us threat our sleds better than that. I'm not sure how the clearance issue plays out: I know it's something you have to pay careful attention to if you're boring and honing to spec, but as I understand it, something like the Wossner replacements are sized to match a bore set up for OE pistons, so the clearance should be correct. It's something I'm going to confirm, of course.

All that said, Dan is a major wealth of knowledge, and stands behind what he sells. I partly want to see for myself how things work - 4032 alloy forged pistons seem like the right fit, but also the difficulty of getting OE pistons is part of the equation. I don't think you'd go wrong with one of Dan's builds though; I'm not trying to discourage anyone from going that direction.

 

[seef158]

This thread is one I've read through several times - https://www.snowest.com/forum/threads/polaris-800-owners-dont-replace-your-stock-pistons.433563/ Dan says all forged pistons fail his test, but it's not something I'd ever do with a sled I own (start with stone cold sled, let it warm to 70F, then immediately run it wide open for a mile). I mention the question of the warranty, and the test makes sense in that light, but I think most of us threat our sleds better than that. I'm not sure how the clearance issue plays out: I know it's something you have to pay careful attention to if you're boring and honing to spec, but as I understand it, something like the Wossner replacements are sized to match a bore set up for OE pistons, so the clearance should be correct. It's something I'm going to confirm, of course.

All that said, Dan is a major wealth of knowledge, and stands behind what he sells. I partly want to see for myself how things work - 4032 alloy forged pistons seem like the right fit, but also the difficulty of getting OE pistons is part of the equation. I don't think you'd go wrong with one of Dan's builds though; I'm not trying to discourage anyone from going that direction.

To be clear I'm doing the work myself. I used to race some snocross and have done a few top ends in my day. I figure with new crank seals and IS testing injectors and or replacing if needed I should be safe. I still feel this was either a bad factory plate job honestly but don't want to wreck a new cylinder. Warranty doesn't cover stupid haha

 

[sledhed]

To be clear I'm doing the work myself. I used to race some snocross and have done a few top ends in my day. I figure with new crank seals and IS testing injectors and or replacing if needed I should be safe. I still feel this was either a bad factory plate job honestly but don't want to wreck a new cylinder. Warranty doesn't cover stupid haha

Makes sense. I also have done quite a few engines over the years, 2 stroke and 4... this time around I went ahead and just ordered new injectors with harness (already in place) and now on second thought and rereading some of the threads on 800 HO motors, I ordered new exhaust valves, the part that sometimes breaks off and (ouch) goes through your motor... again cheap insurance...

 

[davesilb]

To be clear I'm doing the work myself. I used to race some snocross and have done a few top ends in my day. I figure with new crank seals and IS testing injectors and or replacing if needed I should be safe. I still feel this was either a bad factory plate job honestly but don't want to wreck a new cylinder. Warranty doesn't cover stupid haha

I have read through this several times myself and could find no one suggesting what I think happen. I have not seen this on two strokes but have seen it on auto engines. The brown color indicates to me it was sucking a lot of water through the engine. Are you sure the head gasket was not leaking or the cylinder has a hairline crack in it? Did the other cylinder have any brown color to it?

 

[TheBeattie]

I personally won't run Wossner pistons again. They came in my CV Tech short block, and at around 1500km the mag side top ring cracked on the edge of the exhaust port and took out the cylinder with it. I can't find it now but I read somewhere that they changed ring suppliers a few years ago and it was a bad switch. Also the locating pin did not move from the hole its in and I am RELIGIOUS with warming it up before riding

 

[gtwitch]

See the other post from me today, I had a 2018 AXYS 800 go down because of the PTO side main bearing failure and called INDY and they said this was not un common and they have changed the bearing set up on the pto side to 3 bearings instead of the way polaris put that engine out with the extra wide main bearing. as that bearing came apart, it caused small particles of bearing to go up the transfer ports into the pto side cyl and scored the cyl so I had to get a cyl from INDY also and they said to only use Polaris pistons , definately did not like Wossner. Ditto on the pre ride warm up to thermostat open before ride start
gtwitch in wyoming