Polaris Engine and surrounding information

ottawaair · Sep 16, 2013

Paul_Aris said:
How many miles before failure? How many miles are on your aftermarket pistons?

1,700 on stock pistons. i kept an eye on them with a bore scope camera, thru the Y pipe.
I started seeing the piston crown lifting so talked to the dealer. (still under warranty)
They replaced them with polaris pistons, and at that time found the cracked skirt, so replaced the mono-block as well.

When i got it back, i rode it for 300 miles, it vibrated worse than before, and only had 112 psi compression. Had 118 psi before rebuild.

I ordered wossners, and replaced them myself ( **** the warranty).
I now have 700 miles on the wossy's
All around better running sled.

I measured and weighed all the parts when i replaced them.
I recorded all measurements and can go them if needed.
The wossners were by far a better quality piston.

Thinking of a full kit with head this season.

RoffRider · Sep 16, 2013

ottawaair said:
Ok, 1986 Honda CR 500... One huge piston, 500cc's worth.

Correct piston fitment, no broken skirts. hmmmm......

2010 and up cat motors... correct piston fitment. No broken skirts.

Since you have so much knowledge, but haven't opened up your motor yet, Maybe you should tell us what you opinion is.....
Rather than trying to debunk our findings.

well, i dont know what is really wrong with this engine, so i dont know...but from what im told...i think a spacer plate with firm support for the boost port cylinder skirt pegs wouldnt hurt, and with a spacer a longer rod that wont hurt, and aswell as reinforcement for the exhaust side cylinder skirt...i dont know if the cylinder really is the problem...but thats what i think, im not trying to hurt feelings, were all trying to find out what is wrong to help each other

ottawaair · Sep 16, 2013

mtncat1 said:
i'm not buying that. the computer is monitoring engine temp ,and engine air temp continually, refreshed several times a second, the air temp in the air box is going to correct it's self very quickly as the engine pulls fresh air into it as soon as the engine starts up. so this lean condition would be corrected by the time you hit the throttle. if you were talking water temp maybe because it changes much slower.

Just throwin it out there. I don't know how fast the sensor responds to temp spikes.
Plus, i do believe that it is mounted slightly out of the direct airstream, possibly taking longer to cool down.
Im sure the voltage could be read with a digital wrench hooked up to see how fast it responds.

RKT · Sep 16, 2013

This thread is not a thread about what is wrong with the 800 CFI engine.

It is a thread about "myths" that surround this enigne and whay they may or may not be "myths"

Can we try and stay on topic?

rmscustom · Sep 16, 2013

Rkt, Is there a case volume issue?

ottawaair · Sep 16, 2013

RKT said:
This thread is not a thread about what is wrong with the 800 CFI engine.

It is a thread about "myths" that surround this enigne and whay they may or may not be "myths"

Can we try and stay on topic?

Kelsey, you already debunked the myths in the first post.....:face-icon-small-coo

That just leaves us to talk about pistons.:typing:

How about the Myth of having a 2 stroke engive survive any amount of time with epa regulations and ethanol gas.

Silly me, thats not a myth.:crazy:

RoffRider · Sep 16, 2013

rmscustom said:
Rkt, Is there a case volume issue?

thats what bikeman says, they claim 4 hp from a cylinder spacer and a longer piston, not sure if thats right but i asked them about it and they said while primary compression is a good thing, it can also be over done, and that there was not enough air in the crank case to begin with so when they lowered the primary compression ratio they gained power from more air over all...high crankcase compression is usually a gimmick unless it is very low

ottawaair · Sep 16, 2013

I guess i might be confused.
Is this thread about why these motors suffer durability issues, Or why they don't make the hp of the other manufacturers ??

RoffRider · Sep 16, 2013

ottawaair said:
I guess i might be confused.
Is this thread about why these motors suffer durability issues, Or why they don't make the hp of the other manufacturers ??

i have an idea, we take all the info from all our cfi 800 threads, and when we are all done...put them into one big thread... and sticky it...

philsummers21 · Sep 16, 2013

RKT said:
It is about why or why not the claimed issues (see initial post) are valid/true or not? AND , most importantly, why they are valid or invalid

Many may remember last season when the "2013 drive shaft myth" surfaced...
I developed a "fix" for this issue and explained to people why this fix would work and solve their issues. I always try and explain the reasoning behind things.. Just my Engineering training/background , I guess..

MANY came on this forum and told me how the fix I had would NOT work and that the problem was elsewhere (other myths like Bad Glue, faulty assembly at Polaris (sorta like this whole cylinder not plated to the correct size at Polaris thing) etc. etc) and how I was just "band-aiding" a problem and the fix offered would fail in short order ...

There was sound engineering opinions, by myself and others, that supported and did not support the solution proposed... and others that did whatever they could to steer you aways from what was offered as a solution..

THEN.. POLARIS, came up with the exact same conclusion that I came up with.. they (and about 5 other shops around Northern America) came up with the same solution/fix product that I designed and built.. and offered it to ALL ther customers..

Then all the people who told me I was full of it seemed to quiet down and the 2013 Sled owners finished their season (with the fix) without issues...

This is kind of the same thing.. you have many people claiming that certain issues are present... So, I think it would be wise to discuss why they are valid concerns or not..So, not really looking at "fixes" for the time being... looking at finding if the "myths" are true or not... Again.. real hard data to show it valid or invalid..

We can discuss "fixes" and durability concerns in another thread..

But I am looking for SOLID data to support or not support the items in post #1

Solid Data:
2011 Pro 1600 miles. Engine replaced by Polaris due to broken piston skirt and hole in Crank case
2011 Pro 2000 miles (400 new engine) RKTek drop in pistons installed due to preventive maintenance and vibration.
2011 Pro 2600 miles (1000 miles new engine, 600 miles new pistons) Motor continued to vibrate horribly and locked up
2011 Pro 2600 miles (0 miles on Long Rod motor) Will post on honest opinion after this season.

Either way. Pistons alone did not fix my vibration. And yes there is something wrong with this motor.

RKT · Sep 16, 2013

philsummers21 said:
Solid Data:
2011 Pro 1600 miles. Engine replaced by Polaris due to broken piston skirt and hole in Crank case
2011 Pro 2000 miles (400 new engine) RKTek drop in pistons installed due to preventive maintenance and vibration.
2011 Pro 2600 miles (1000 miles new engine, 600 miles new pistons) Motor continued to vibrate horribly and locked up
2011 Pro 2600 miles (0 miles on Long Rod motor) Will post on honest opinion after this season.

Either way. Pistons alone did not fix my vibration. And yes there is something wrong with this motor.

Good data, thanks for sharing..

Sounds like you had a crank issue from the start with your replacement engine.. we see that often where the replacement crank has excessive run out . We find the MAPE crank to be one of the issues with this engine.. Fortunately, there is a new crank . from Polaris, that seesm to help with this..

Thanks for the info...

philsummers21 · Sep 16, 2013

Very well could be. That was my thinking hence the LR motor with new crank. Still the funnest sled ive owned

tinkerjohnson · Sep 16, 2013

X2

rmscustom said:
Rkt, Is there a case volume issue?

This is another topic that comes up, I have read about this several different places. I also would like to know what others (engine builders ) think about this

tinkerjohnson · Sep 16, 2013

philsummers21 said:
Solid Data:
2011 Pro 1600 miles. Engine replaced by Polaris due to broken piston skirt and hole in Crank case
2011 Pro 2000 miles (400 new engine) RKTek drop in pistons installed due to preventive maintenance and vibration.
2011 Pro 2600 miles (1000 miles new engine, 600 miles new pistons) Motor continued to vibrate horribly and locked up
2011 Pro 2600 miles (0 miles on Long Rod motor) Will post on honest opinion after this season.

Either way. Pistons alone did not fix my vibration. And yes there is something wrong with this motor.

I would guess it was a crank issue aswell all the pistons I have installed (rkt) have taken the vibration away, it's very noticeable with stock pistons vs rkt

scott t · Sep 16, 2013

So if its just a piston issue. Wouldnt the 600's be experiencing the same thing? I know they are two different engines but wouldnt they both have polaris cast pistons? And the 6 has good performance for a 6 with way less issues than the 8. Im not an engine builder as my post probably show. Just trying to learn from these threads as I am or will be looking into alternatives when my warrenty is up.

Vfrtrader · Sep 16, 2013

In short: There is absolutley no rod ratio issue. If there were, then Cat and Ski Doo would be suffering even worse. Again, opinion only , but opinion based on real data, text book design criteria, and experience

Kelsey,
Would you say Cat and Doo hasn't had broken skirt issues because they pistons fit better than Polaris'?

Snodawg · Sep 16, 2013

It sure seams like it is hit or miss with these motors. I have seen many reports of these motors running a real long time (3000+ miles) with no issues. I myself have 2000 miles on my 11. No issues. I pulled compression on it just recently (125+ psi, both cylinders, hot and cold). I don't want to start something here, so I will try to be careful, but I feel it needs to be addressed. How are these motors with failures being treated? Myself, I am very diligent about every time I fire up my sled, I try to let it warm up to around 120 before I sled off into the distance. Please don't take this as an accusation, just more of an inquiry.

As far as case volume is concerned, I hear of conflicting reports. Some builders say that an increase in case volume is what these motors need. Others say not to increase case volume (ie: long rod, spacer plate etc.) as this will hurt bottom end torque. So who is right? BTW, these are all top notch reputable engine builders. Sounds like some myths to me..

I have also heard differing opinions (from same engine builders) on types of pistons. Some swear by forged pistons and others say there is absolutely nothing wrong with the stock pistons. Just change out the pistons at around 1500 miles regardless of whatever type of piston is used. They just simply wear out quickly and need to be changed out more often.:noidea:

RoffRider · Sep 16, 2013

Snodawg said:
It sure seams like it is hit or miss with these motors. I have seen many reports of these motors running a real long time (3000+ miles) with no issues. I myself have 2000 miles on my 11. No issues. I pulled compression on it just recently (125+ psi, both cylinders, hot and cold). I don't want to start something here, so I will try to be careful, but I feel it needs to be addressed. How are these motors with failures being treated? Myself, I am very diligent about every time I fire up my sled, I try to let it warm up to around 120 before I sled off into the distance. Please don't take this as an accusation, just more of an inquiry.

As far as case volume is concerned, I hear of conflicting reports. Some builders say that an increase in case volume is what these motors need. Others say not to increase case volume (ie: long rod, spacer plate etc.) as this will hurt bottom end torque. So who is right? BTW, these are all top notch reputable engine builders. Sounds like some myths to me..

I have also heard differing opinions (from same engine builders) on types of pistons. Some swear by forged pistons and others say there is absolutely nothing wrong with the stock pistons. Just change out the pistons at around 1500 miles regardless of whatever type of piston is used. They just simply wear out quickly and need to be changed out more often.:noidea:

well as for your comment on crankcase volume, it kindof depends, a good 2 stroke with a wide powerband and respectable top end hp peak uses the pipe pulling power(pipes can creat a vacum bigger than you think) alot more than crankcase compression, the problem with more crankcase compression is it forces air into the cylinder through the transfer ports very violently and uncontrollably, in the carbed days this was a big problem cause lots and lots of fuel/air would escape out the exhaust when you arnt in the power band, lowering crankcase compression would mean more air/fuel in the case to charge the cylinder, but it would be very slow in filling the cylinder, a good pipe design would make up for this

the polaris also has a goofy cylinder skirt design and its like a triangle thing, i imagine if you square those out to the edge of the transfer ports you can pick up some gains

Angermangement890 · Sep 17, 2013

2011 Polaris Rush Pro-R all stock, no engine mods, punted cylinder skirt out of the case at 2200 miles, running Polaris oil

2012 Polaris PRO RMK, engine replaced by Polaris due to same issue as above. Polaris engines back ordered mid season 2013, 2011 engine installed by dealer, ran like crap, poor compression, cyl measures .0035" out of round. Crank wheel damaged, Reeds are torched at the tips from excessive heat in the lower end. Polaris warranty says no help as they already installed a new engine. Running Polaris oil

2010 800 IQR Carb engine, poor compression reeds are torched, excessive heat in the case, I did not measure the bore myself, there was so much slop in the bore at TDC that I could stick a .025" feeler guage between cyl and piston at TDC. I know this isnt an accurate measurement of the the bore, but seriously .025" of slop at TDC... Something isn't right.

All 3 engines now long rodded... I dont expect there to be any issues this season, or next or the following one either.

RKT · Sep 17, 2013

Vfrtrader said:
Kelsey,
Would you say Cat and Doo hasn't had broken skirt issues because they pistons fit better than Polaris'?

No, I would not really say this,,

The Ski Doo and Cat pistons actually fit LOOSER in the bore than the OEM POLARIS piston.. The OEM Polaris piston is actually the tightest fitting piston (when new) of all the manufacturers... you can measure for yourself and see.
What we see is that the piston quickly begins to collapse the skirt.. so, that once ,real tight, clearance becomes looser and looser as the miles are put on... eventually, the fatigue sets in and the skirt breaks usually taking the cylinder and case with it.
We have yet to see a cylinder that is out of spec or out of round.. that is not to say that it can not happen but is is certainly not the "norm"..

ALL 2 stroke snowmobile Pistons are heavily tapered from the skirt to the crown.. There are good reasons why they are designed this way. The top of these OEM pistons seems to fair just fine.. but you will ALWAYS have huge piston to cylinder wall clearances when measuring at the top of the piston to the cylinder.. This is fine..
Compression checks on the engine will not tell you anything about the condition of the lower half of the piston.

So, the compression can and will be fine but you could have a major lower piston skirt issues present.. In fact, you can break off the entire lower half of the piston, do a compression check and it will check out fine.. That is why you really have to inspect the lower half of the piston in order to see any issues...

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