800 cfi Piston Replacement

[pj8556]

Am considering replacing pistons on my sled. 1000 miles on original (updated) motor and no problems, runs great but I dont want a piston to fail like so many others and take out the whole motor, $200 is alot more reasonable than $4000!

Anyway, cant decide on pistons. Was thinking Wiseco, but my buddy who is gonna order them for me recommended SPI. Said something about Wiseco and the cold not being a good combo.... ?? Thoughts?

THANKS!!

 

[sled_guy]

I'd pull the exhaust valves and look in at the pistons. If they aren't scuffed and look good I wouldn't pull it down.

Why fix something that isn't broken?

sled_guy

 

[penguinpoo]

Why not wait awhile and keep an eye on "the fix". Check out the post on this forum.

 

[2strokes_are_awesome]

I would keep running the lucky set that you have if its working right. The oem pistons aren't the "right" replacement IMO and I think many would agree. The fix kit from pms is your best bet on having a reliable engine as far as new pistons. Plus most people say the sled runs better than ever after they put the kit in.

I'll know soon enough as I should have mine together today with the fix kit assuming that the local dealer has the little green injector o-rings and new ev gaskets.

 

[Stroker Customs]

I think you should replace the pistons as I am one of those that had one come apart and take out the whole motor. The problem is not scuffing its the short piston that rocks back and forth in the cylinder causing skirt and ringland wear over time. When you pull your piston you will see what I am talking about. On the exhaust side look at the top of the piston around the rings you will see wear then on the throttle body side look at the skirt of the piston you will see wear. I like to replace the pistons about once a season unless you are putting on 3000 miles a year then do it twice. There are some different options if you want to fix this problem. But its all in what you want. You could just order a carls 860 for instance or you could stay stock and a few people out there are addressing the issue.

 

[INDEEP]

I think you should replace the pistons as I am one of those that had one come apart and take out the whole motor. The problem is not scuffing its the short piston that rocks back and forth in the cylinder causing skirt and ringland wear over time. When you pull your piston you will see what I am talking about. On the exhaust side look at the top of the piston around the rings you will see wear then on the throttle body side look at the skirt of the piston you will see wear. I like to replace the pistons about once a season unless you are putting on 3000 miles a year then do it twice. There are some different options if you want to fix this problem. But its all in what you want. You could just order a carls 860 for instance or you could stay stock and a few people out there are addressing the issue.

I'm with PDP. My pistons looked good too at 600 miles. After a skirt broke the whole motor is junk. Don't go with the OEM pistons they have too much slop. Go with Weisco's or the PMS Fix and make sure you always warm the motor up plenty.

 

[milehighassassin]

I have been thinking about changing my pistons as well. I don't think the OEM pistons are the solution for they have too much slop. I have also heard that the Weiscos have a lot of slop as well. Maybe the PMS is the sollution.

Edit... I just read "The Fix" uses Weisco pistons.

http://www.pmspolaris.com/thefix.htm

 

[thefullmonte]

I have been thinking about changing my pistons as well. I don't think the OEM pistons are the solution for they have too much slop. I have also heard that the Weiscos have a lot of slop as well. Maybe the PMS is the sollution.

Edit... I just read "The Fix" uses Weisco pistons.

http://www.pmspolaris.com/thefix.htm

The Wiseco pistons bring things right into correct tolerance. So they aren't a sloppy piston. They are also a much more consistant diameter piston from top to bottom. The OEM pistons measure narrow at the top and bottom and have a very small area 10mm up from the bottom where you are supposed to measure. Even there I was getting clearance of .0068. Out of acceptable tolerance. So that was at the widest point. The Wiseco was a very consistant .005 piston to cylinder clearance.

I think the fix is probably the way to go. Otherwise you are still dealing with crank throw generating side forces on the pistons. I spoke with SLP yesterday and man the issues with these sleds are never ending. I think my fix is to get something different when I can afford it. That won't be for awhile.

 

[rmkboxer]

wisecos are good pistons but they are known for cold seizures

 

[Polarisrocks]

So i have doven into the polaris cfi piston nightmare to help a friend. We tore one down his to find a big mess on a 500 mile sled, the mag piston ring had broken at the tips that cover the pin and they have made a mess of the cyliner and head and how much went into the cases/bearings. So we have contacted our dealer to find out why we have a cylinder that is out of specs 10 thou cylinder wall clearance!!! and have broken piston rings after 400 miles. Our local dealer put new pistons in at 99 miles, polaris's piston update. Do you think any of the dealer checked piston to cylinder clearances?? NO All they were told is to check ring end gap and make it 16 to 20 thou. So is there a cylinder expansion problem?? Is the reason they are running them sooo sloppy is to avoid a seizure problem? Did they switch pistons and figure that it would bite them in the a$$ this bad. Or are they handing out out of spec parts or assembling engines from the factory with bad out of spec parts and telling their dealers to turn their heads?? Should our dealer have checked the cylinder clearances and sent that set of cylinders back to polaris.... yes, did they.. NOPE, and frankly I am done with polaris!!
I think if polaris keeps handing out sh!t sleds year after year when is enough and how much money is enough. Polaris should of stood behind the 800 twin crank failures, did they, NOPE.. Are they standing behind the piston nightmare... nope. what about the 900.... when is enough folks??

 

[INDEEP]

Well said!

 

[754bigbore]

Totally agree with you guys! Have been a polaris fan for years now, but now I am stuck with a sled that no one wants and don't have a choice but find a fix so I can ride it. I have 900 miles on it and the pistons still look very good, but I know it is a matter of time. I will probably get the "fix" too after this season. Should probably do it now before the whole engine gets destroyed but financially not possible.

 

[R44guy]

I think you should replace the pistons as I am one of those that had one come apart and take out the whole motor. The problem is not scuffing its the short piston that rocks back and forth in the cylinder causing skirt and ringland wear over time. When you pull your piston you will see what I am talking about. On the exhaust side look at the top of the piston around the rings you will see wear then on the throttle body side look at the skirt of the piston you will see wear. I like to replace the pistons about once a season unless you are putting on 3000 miles a year then do it twice. There are some different options if you want to fix this problem. But its all in what you want. You could just order a carls 860 for instance or you could stay stock and a few people out there are addressing the issue.

This is a huge and never ending subject with these polaris 800 cfi engines when it comes to oem pistons and failures!

I would suggest to anyone who has one of these engines to be proactive and to change your pistons before you have a problem so it costs you less money and less down time.

I changed mine at about 100 miles to the fix with the slightly larger and taller wiseco piston and it has worked flawlessly and never better. I do not need to explain this kit as many of you have read the thread on this kit.

The biggest concern with waiting is if you have a failure you risk damaging a rod bearing and having a crank failure down the road. When the oem pistons brake the skirts off the broken parts of the piston can cause other damage that can lead to eventually needing a case or case half, cylinder, crankshaft or even possibly damage the head if parts end up on top of the broken up moving mass. So if you do nothing it can eventually cost you even more!

Otherwise you can get some good insurance coverage with a $50 deductible and lose control and hit a tree or send her off a cliff you may be better off providing your buddy doesnt post this exercise on you tube! We will then know in a few years if the polaris 800 cfi sleds have had more insurance claims then any other sled before in the insurance industry! Ofcourse there are other liabilites to this if you get caught like sleeping away from home for a while and not being able to make a living unless you have always wanted to make license plates.

 

[Polarisrocks]

Has anyone measured the 2010 cylinders? is the skirt thicker is the bore the proper size and how much needs to be taken out of the cases for them to fit. I think the oem piston is fine, i think its the slop... Millenium said they could renic the cylinders to the proper specs of your piston and you would be done. So for a few dollars in gaskets and some down time waiting for a cylinder from millenium you could have piece of mind knowing your motor has proper specs and may last. Now you may have to do some ring end gap clearancing to make the oem piston rings work, but i think oem piston is superior to wei(seize)co. Now I was also told from my dealer that polaris has renic part number that comes from US CHROME... so if you buy a new cylinder are you getting a reniced cylinder or are they all being resized and nicked?? Has polaris caught on to this??

 

[R44guy]

Has anyone measured the 2010 cylinders? is the skirt thicker is the bore the proper size and how much needs to be taken out of the cases for them to fit. I think the oem piston is fine, i think its the slop... Millenium said they could renic the cylinders to the proper specs of your piston and you would be done. So for a few dollars in gaskets and some down time waiting for a cylinder from millenium you could have piece of mind knowing your motor has proper specs and may last. Now you may have to do some ring end gap clearancing to make the oem piston rings work, but i think oem piston is superior to wei(seize)co. Now I was also told from my dealer that polaris has renic part number that comes from US CHROME... so if you buy a new cylinder are you getting a reniced cylinder or are they all being resized and nicked?? Has polaris caught on to this??

Rocks, Anything has to help with the factory polaris tolerance issues, It sounds like you dont like the wiseco forged style pistons and everyone has there own exierence and opinions so I respect that.

The issue I see with the polaris pistons is that the height of the piston is shorter then alot of other style pistons which is one of the main reasons why the loose tolerance's allow the piston to slap or rock in the cylinder and eventually with some heat expansion and wear that the piston skirts would break off.

this is one of the main factors why the fix kit from pms has some other advantages besides addressing and fixing the tolerance issues the piston is built taller and the cylinder shim is used to accept the same stroke with out changing the engine timing.

I too have heard from some that wiseco pistons are more prone to cold seizes but you need to warm these engines up to be safe and there for shouldnt be a factor.

I think you are making a big improvement and wish you luck with your repairs and changes. Are you running the latest april map or a pcv?

 

[Polarisrocks]

I guess i could have an open mind to weisco... from past experiences I swore I would never touch another one...
I measure the cylinder today and it specs 3.3450 at top and bottum, but the new and old pistons spec 3.3125 on top and 3.3415 on bottum..
So the piston is 36 thou smaller than the bore on top and has only 10 thou on the bottum... Why would the pistons be so tapered?? I see the bottum to the polaris spec of 5 thou but what about the top? Does the weisco had the same specs?

 

[milehighassassin]

Pistons are tapered because different parts of the piston heat up at different rates. Metallurgy.


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[thefullmonte]

I guess i could have an open mind to weisco... from past experiences I swore I would never touch another one...
I measure the cylinder today and it specs 3.3450 at top and bottum, but the new and old pistons spec 3.3125 on top and 3.3415 on bottum..
So the piston is 36 thou smaller than the bore on top and has only 10 thou on the bottum... Why would the pistons be so tapered?? I see the bottum to the polaris spec of 5 thou but what about the top? Does the weisco had the same specs?

As milehighassassin stated that the piston heats at different rates. The piston composition also plays into this. We can read into this a couple of different ways.

1. The OEM piston is of poor quality and has a very high expansion rate.
2. The piston is designed to expand, but never achieves the ideal heat to do so.

There seems to be a fix for both of these scenarios. Either way, the OEM pistons just don't seem to work well with this setup.

Remember that the crank throw is also an issue with these motors. It is adding a tremedous amount of side force to the piston. This is causing premature ring wear and ring land failure as well as piston skirt wear. So if the top of the piston isn't achieving optimal expansion it could still be allowing the piston to have some excessive tip inside the cylinder.

It has been my understanding that this motor design was developed from their race program. I see far too many variables with this. Race motors are maintained differently than consumer motors. These motors get proper fueling and heat differently. Most race programs usually operate with only the highest quality parts meaning everything has very precise tolerances.
Gets a person thinking anyway.

As for the Wiseco pistons. I don't know what I did with my measurements, but they had very little variance from top to bottom. They were much more consistant.

Wiseco earned a bad rep 20+ years ago. We used to say, "Wiseco, yeah I'm stuck on them". That was the joke, but the company is bigger than ever and making pistons for everything that needs one.

The same technology used in cast pistons is also being utilized by Wiseco in their forging process. This includes low friction coatings. And different materials being impregnated in the metal for heat tolerance and to control expansion.

I'm just more used to foreign motors I guess. Much tighter tolerances and far less failures. That is probably why I identified the piston slop as an issue back in 08. It had me shaking my head back then. And that is what got me looking for an aftermarket solution. There are other options, I just know that the Wiseco pistons brought everything well within spec so that is the route I chose.

Sorry about the long read. Just trying to shed a little more light.

 

[milehighassassin]

Monte

Did you use the regular wiseco pistons or did you use the "fix" pistons and shim kit?




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[gerrman]

There appears to be three options to address the stock piston clearance but all three do not address the piston rocking issue.

1. ReNic the cylinders to increase its thickness to bring stock pistons
into spec(.005"). Rocking issue addressed? Is this a band-aid fix?

2. Replace stock pistons with Wisecos to .005" spec. Does this address
the rocking issue the same as or different than #1?

3. Use the "Fix Kit" from PMS. This kit brings pistons into spec(.005") with
custom Wiseco pistons and address's the rocking issue with a longer
piston. This kit seems to address both issues that #1 & 2 do not.

So the question is , which is the best option? Monte, what are your thoughts. My engine warranty runs out at the end of this season and I want to do something.