Piston to Cylinder Clearance Confirmed! Not Good!!

[akrevrider]

The Fix Kit & a Turbo?

So has anyone run the 'fix' kit with a turbo? Any issues??

Iowarmk, a member here on the forums, just installed the Fix Kit on on his Dragon 800 with a Turbo. It is running but don't know if he has tuned it yet.


akrevrider

 

[WyoBoy1000]

I'm just curious and learning here so don't take this wrong.

Thats kind of scary to see that much wear with so few miles, what turbo kit are you using, how much boost. I have ran from 6-12lbs and have 2000 miles, turbo'd since day one on a m8 and it looks perfect, wondering if its just the pistons that caused them to look like that or maybe other causes. I have seen some other poo 800 motors that still looked pretty good I thought at 1000 miles of boost, (the guy is good at tuning) or maybe just lucky. Seems like the wisco's are good

 

[theshadowrider]

No worries wyboy. Comparatively to other Polaris pistons they are a in good shape. This is one of the problems with these engines. Its crazy that at such low hours, other Polaris owners tell me that my pistons are in good shape because the way others look. Seems the two major reasons these Polaris sleds keep going down is lean midrange, and piston clearance. Its like, "why are we breaking piston skirts off at 300-400 miles." The tolerance are way to loose. I am learning and forming my own opinions also but so far I am not impressed with the stock pistons so I am going with aftermarket. I am running a BD turbo kit and if anything they, "turbos" seem to prolong the engine life compared to NA sleds. Not sure if its the increase pressure reduces slap, or the increase heat decreases tolerances but a turbo dragon seems to hold up better than a NA.

 

[WyoBoy1000]

I have seen a lot of them that just had a bd box for tuning prolong the life, I think it has something to do with helping the injection system maintain or smooth out fuel supply. It would be nice to see some measurements on new pistons to see if they are straight or not. I have found on a lot of two strokes if you keep the egt under 1200 ( I like 1150 range) they rarely break skirts, unless coolant temps get to high that will do it also. One year on a dirt bike I was breaking skirts every 2 weeks from hill climbing on hot days, pretty sure it was from extreme coolant temps. I have also heard if 2 strokes hit something like 172* or above there is a risk for the pistons to swell to much and 4 corner seize. (just what I heard, but kinda makes sense) If I was on a poo I would prob be running egts, O2 gauge, coolant, and charge tube sensors for a while to see just what was happening. Then if you where to cook something you would know how far you can go, or figure out different tuning methods to save it. Once you get it dialed you could remove most of it. I know its over the top but once you can actually see everything happening it all makes a lot more sense.

 

[theshadowrider]

Update

Thought I would post and update. I have had three rides on my sled with the wiseco pistons. They are working awesome. I did a few heat cycles and then took it easy the first ride for breaking it in. Only ran it at 8lbs boost and ran extra oil, and didn't hold steady throttle. Last ride out I turned it up to 10lbs and did some long pulls. Runs great under boost. What have I noticed? My EGTS seem to run more consistent, usually always withing 25 degrees of each other. Seems to idle smoother and quieter. After a few more rides I am going to check compression and pull my exhaust valves and see how they look. I feel a lot more confident this year in my engine than any previous years. So far I would endorse them! I will check back after running 14lbs!

 

[pus1100]

Thought I would post and update. I have had three rides on my sled with the wiseco pistons. They are working awesome. I did a few heat cycles and then took it easy the first ride for breaking it in. Only ran it at 8lbs boost and ran extra oil, and didn't hold steady throttle. Last ride out I turned it up to 10lbs and did some long pulls. Runs great under boost. What have I noticed? My EGTS seem to run more consistent, usually always withing 25 degrees of each other. Seems to idle smoother and quieter. After a few more rides I am going to check compression and pull my exhaust valves and see how they look. I feel a lot more confident this year in my engine than any previous years. So far I would endorse them! I will check back after running 14lbs!

struggeling with sloppy oem piston in my 2011 pro,thinking of going the Wiseco route.have you measured the squish clearances,stock and Wiseco?are there any differences.maybe small enough to get away with a extra cylinder base gasket?

 

[theshadowrider]

struggeling with sloppy oem piston in my 2011 pro,thinking of going the Wiseco route.have you measured the squish clearances,stock and Wiseco?are there any differences.maybe small enough to get away with a extra cylinder base gasket?

No, I didn't check either. I am guessing its close to stock based on compression readings.

 

[miller tools]

specs

Does any one have the TQ specs iam doing MTNTK kit and dont have the bolt TQ specs thank you

 

[theshadowrider]

Does any one have the TQ specs iam doing MTNTK kit and dont have the bolt TQ specs thank you

Not sure if you have already found this, if not here you go.

 

[miller tools]

THANK YOU

 

[sledhed]

Wow, they have a torque sequence on the recoil cover... I would have never thought... just put a new rope in my wife's 700, did not even think of doing a criss-cross type sequence on that cover.

 

[theshadowrider]

Another Update

Wiescos pistons are working awesome on boost. Put them through the paces last time out. Ran 12 lbs boost on multiple runs and got the EGT's fairly hot. All seems to be working good. I am at 9500' running 50% avgas. I have 3 day trip to the Unitahs and after that trip I will pull my exhaust valves and see if I can see anything.

 

[madmax]

Shadow,

GREAT WRITE UP!!

A couple of things to mention though... used pistons will often have different dimensions from wear due to fuel/lubrication differences because the cylinders are divorced... also the differences in cyl temp that can be inherrent in these designs (you cant get the coolant flow exactly the same in both cyls)... can cause wear on the pistons etc.

The Wiseco pistons, being a forged piston, will have different characteristics than the cast pistons... as well as specific warm-up needs... IMO, make sure you pay very close attention to this.

The OEM for the stock pistons, Elko from Europe (Austria) has some of the highest quality standards in the industry that I know of... and their pistons are some of the most abuse resistant in the two stroke industry that I know of... This however does not mean that they will hold up to a problematic motor design....

On the turbos though... after seeing the abuse that Kinzer put his uber-high mileage sled through with stock pistons... I feel that the turbo sleds have been having better luck than the N.A. sleds out there with the 800 cfi.

I'm also curious... what are the thickness' of the wiesco rings / OEM... and is the skirt length identical on the two different pistons... How bout the wrist-pin-center to dome-top dimension??

I would listen to mountainhorse here. The stock clearance from Polaris is for stock cast pistons. Cast pistons don't require as much clearance, as they don't expand as much when heating up. A forged piston (weisco) is stronger, but expands more when heated therefore require looser tolerances. .004-.005 is very tight for a forged piston. you are at much increased risk for cold sieze. I would make you find out from wiesco what they recommend for clearance, I bet it's closer to .007". Make sure let it warm up real good each time after starting or you'll be replacing those wiescos in no time

 

[gus bohne]

Before wiseco makes a piston they make sure all dimensions are exact match to the OEM piston they are replacing.

In the 33 yrs Ive been using wisecos without a single problem they have never been different in the timing dimensions than the oem they replace.

timing dimensions are pin to deck, pin to skirt bottom and ring pin location..
Always nice to close all 3 exhaust ports at TDC unlike many crossmatched oem cast pistons.

crossmatched means fits many different models within the brand ,, fits physically means nothing when the ports are left open or the locator pins are on the edge of a transfer window...Yucky red solo cup !!!

Glad to see so many POO turbos running quietly and happily on forged pitons,, makes me even happier knowing those with brand X turbos aren't buying flippers for them when they lose a cast skirt or ring land..

I will happily provide the wiseco piston of your choice for SKIRT breaking..I ve read some old wives tales about wiseco skirt breakage,,,, show me,, its forged,, it takes a sledge hammer and 2 foot long channel lock pliers to manhandle LONG ENough to brake one,, you cant deform one that much or bend it back and forth that far in a running engine. Unless of course,, the rod you broke FIRST sent it through the cases !!! LMAO
gus


We take them from 65 degree coolant temp and hit them with 25 psi instantly.. no worries,, its NICASIL...aluminum expands at very close to the same rates,, so its a non issue since we went to coated bores and dropped the old wives sleeves....

testing....005 max or you WILL roll the dome from excessive clearance..
WE have grown out of the stone age no more cast iron...

 

[theshadowrider]

I would listen to mountainhorse here. The stock clearance from Polaris is for stock cast pistons. Cast pistons don't require as much clearance, as they don't expand as much when heating up. A forged piston (weisco) is stronger, but expands more when heated therefore require looser tolerances. .004-.005 is very tight for a forged piston. you are at much increased risk for cold sieze. I would make you find out from wiesco what they recommend for clearance, I bet it's closer to .007". Make sure let it warm up real good each time after starting or you'll be replacing those wiescos in no time

No, wiseco recommends stock clearance. IMO warmup is no different than stock sled. 2816 (Forged Pistons) thermal expansion is only 15% more than 4032 (cast piston). That may seem like alot but to put that in perspective, if your Cast piston expands .003" than a forged piston will expand .0034". So only .0004" more on a 80mm piston. I also spoke with Wiseco rep and asked them if they are using 2816 on the snowmobile pistons. He said on the new snowmobile pistons they are using a hybrid material. He said it has the strength of 2816 and the expansion properties closer to 4032. I asked if he knew the thermal expansion coefficient he said he didn't have it but it was less than 2816, which is minimal IMO. He wasn't an engineer so I am little suspicious, but he did seem to know the snowmobile industry pretty well after speaking with him for about 30 mins.

Update: I have got about 500 miles on my wisecos and have been running them hard. Yesterday we went out in the best snow we have had yet. Finally! Turned the boost up and made a couple runs at 14 lbs. 14lbs is nuts! Wisecos held up great. I am going to pull the exhaust valves now and see if I see anything! Now I am not nervous that at any moment I am going to break a skirt off and put a hole in the case taking out my motor......again! I am with (Gus) on this one, get rid of the archaic cast pistons, and quit putting holes through engine cases!

 

[Snowbird11]

I am going to pull the exhaust valves now and see if I see anything!

any updates?

I only have a couple hundred on mine but they look great from the exhaust side and what i can see of the intake. I'm just curious to know how other folks are doing with the fix kit/wiscos.

 

[Scott]

THIS IS A GREAT POST!!!

Not sure if you have already found this, if not here you go.

 

[theshadowrider]

any updates?

I only have a couple hundred on mine but they look great from the exhaust side and what i can see of the intake. I'm just curious to know how other folks are doing with the fix kit/wiscos.

Update: finished the season turning boost up to 15 lbs. i saw peak egt 1300. I have about 600 miles on the pistons. This summer i pulled my eghaust valves and inspected. From what I could see wear looked good. No scuffing and minimal wear on the piston. Pistons still had coating on them. I am sold on them. I want to do a strenght test on wisecos piston skirts verus stock cast piston skirt. Think that would be interested to see how much force it takes before they break off as this is what I was worried about the stock pistons. Fyi i have already broke a skirt of and put a hole in the case with oem pistons.