Just a little FYI on the Polaris CFI Engine and surrounding rumors

[RK Tek]

I thought it may be helpful to post a little info on this engine and the large amount of "information" that surrounds this engine. I think S&M may have the more level headed members and HOPE that this thread can stay civil..

PLEASE take it as ONLY MY opinion (even though there are many other engine experts (including the manufacturers) who share this same opinion), but an opinion BACKED UP by REAL DATA (not theory or hear-say) and decades of experience

1) Rod Ratio is lacking: FACT: Polaris 800 CFI has the BEST rod ratio of any of the , modern, 800cc engines out there. The rod ratio is actually on the HIGHER end of the "acceptable" spectrum. Yes, there exists design guidelines for all engine builds.. and , again, the rod ratio of the CFI 800 is th ebest out there.

In short: There is absolutley no rod ratio issue. If there were, then Cat and Ski Doo would be suffering even worse.

2) There is a "Cold Shot" that causes engine failure: This is a good one and a huge gimmick.. Arctic Cat has had the SAME type as Polaris of coolant system for ever (no by pass loop) and has no issues .. the difference between Cat and Polaris is Polaris has a digital gauge so you can see the actual temps.. Cat has the same temps but no gauge.. Install a gauge on the Cat and ,SUDDENLY, it will have a Cold Shot problem as well... Only Ski Doo utilizes a by-pass loop and they only started doing this in 2000. For more details on why this is simply not an issue please check out this article:

3) The cylinders, from Polaris, are sized wrong as delivered: This could be one of the biggest falsities of them all.. The simple fact is that the cylinders, when plated, are all plated to within .0005" of each other. This spec is a requirement and is inspected at the factory before installed on the block. RK Tek, as well as, many other Shops, have inspected a large number of these cylinders, ALL, I mean ALL, have fallen within the given spec.

Think about what kind of error it would take to have this SIMPLE inspection/operation "SLIP" by at a HUGE manufacturing facility like Polaris. Polaris has been doing this same manufacturing bore size inspection for over 50 years they are not suddenly going to quit checking cylinders or, worse yet, plate them to the wrong size.....

Think about what a major screw up this would be and how hard it would be for this to be "over-looked" THEN... couple that with the countless cylinders that have been measured (all in spec) and you can realize how rediculous this rumor really is..... Again, simply one person's opinion.

4)(A little off the topic..but related) There is an aftermarket product that you can purchase that has a 3 year warranty on the entire engine: Without getting into any debate.. This is SIMPLY FALSE.

It is very unfortunate that people are mis-lead to believe this kit offers such a coverage.

It is not my intent to say anything postive or negative about any other product out there. BUT--> PLEASE, do not think that there is ANY 3 year engine failure aftermarket product available today!!

Please read the details and NOT the INTERNET FORUMS regarding this... What is covered with this "kit" is the crank and and cylinders from BREAKING!! AND ONLY IF the product is INSTALLED by the MANUFACTURER (which is totally understandable)!!! If you install the SAME products yourself.. NO WARRANTY ..

YOU SQUEAK a piston or Break a Piston--> NOT COVERED.. PISTONS ARE NOT COVERED!!
AGAIN, not saying ANYTHING negative, AT ALL, about this kit.. Just pointing out a few misconceptions that surround its "warranty" AND this thread is about misconceptions.. so, I felt it fit the mold..

Please guys... Let's not turn this informative thread into something it is not.. It is simply opinionated information, that , hopefully, SOME will find useful........

Peace

 

[recguy]

I thought it may be helpful to post a little info on this engine and the large amount of "information" that surrounds this engine. I think S&M may have the more level headed members and HOPE that this thread can stay civil..

PLEASE take it as ONLY MY opinion (even though there are many other engine experts (including the manufacturers) who share this same opinion), but an opinion BACKED UP by REAL DATA (not theory or hear-say) and decades of experience

1) Rod Ratio is lacking: FACT: Polaris 800 CFI has the BEST rod ratio of any of the , modern, 800cc engines out there. The rod ratio is actually on the HIGHER end of the "acceptable" spectrum. In short: There is absolutley no rod ratio issue. If there were, then Cat and Ski Doo would suffer even worse.

2) There is a "Cold Shot" that causes engine failure: This is a good one and a huge gimmick.. Arctic Cat has had the SAME type as Polaris of coolant system for ever (no by pass loop) and has no issues .. the difference between Cat and Polaris is Polaris has a digital gauge so you can see the actual temps.. Cat has the same temps but no gauge.. Install a gauge on the Cat and ,SUDDENLY, it will have a Cold Shot problem as well... Only Ski Doo utilizes a by-pass loop and they only started doing this in 2000. For more details on why this is simply not an issue please check out this article:

3) The cylinders, from Polaris, are sized wrong as delivered: This could be one of the biggest falsities of them all.. The simple fact is that the cylinders, when plated, are all plated to within .0005" of each other. This spec is a requirement and is inspected at the factory before installed on the block. RK Tek, as well as, many other Shops, have inspected a large number of these cylinders, ALL, I mean ALL, have falled within the given spec.

Think about what kind of error it would take to have this SIMPLE inspection/operation "SLIP" by at a HUGE manufacturing facility like Polaris, who has been doing this same manufacturing bore size inspection for over 50 years.. When you think about what a major screw up this would be and how hard it would be for this to be "over-looked" THEN... couple that with the countless cylinders that have been measured (all in spec) and you can realize how rediculous this rumor really is Again, simply on person's opinion.

4)(A little off the topic..but related) There is an aftermarket product that you can purchase that has a 3 year warranty on the entire engine: Without getting into any debate.. This is SIMPLY FALSE.

It is very unfortunate that people are mis-lead to believe this kit offers such a coverage.

It is not my intent to say anything postive or negative about any other product out there. BUT--> PLEASE, do not think that there is ANY 3 year engine failure aftermarket product available today!!

Please read the details and NOT the INTERNET FORUMS regarding this... What is covered with this "kit" is the crank and and cylinders from BREAKING!! AND ONLY IF the product is INSTALLED by the MANUFACTURER (which is totally understandable)!!! If you install the SAME products yourself.. NO WARRANTY ..

YOU SQUEAK a piston or Break a Piston--> NOT COVERED.. PISTONS ARE NOT COVERED!!
AGAIN, not saying ANYTHING negative, AT ALL, about this kit.. Just pointing out a few misconceptions that surround its "warranty" AND this thread is about misconceptions.. so, I felt it fit the mold..

Please guys... Let's not turn this informative thread into something it is not.. It is simply opinionated information, that , hopefully, SOME will find useful........

Peace

Good read and thanks RK Tek. My question to you is why should I install the head and pistons from RK Tek? If polaris factory motors have a tendency to fail then sure it would be a good idea, but i am not seeing engine failures of any sort with the group i ride with.
Appreciate your time.

 

[RK Tek]

Good read and thanks RK Tek. My question to you is why should I install the head and pistons from RK Tek? If polaris factory motors have a tendency to fail then sure it would be a good idea, but i am not seeing engine failures of any sort with the group i ride with.
Appreciate your time.

Great question

Here is what we have seen over the years with this engine (dating clear back to the 2008 IQ Chassis)

The pistons, when new, are properly sized... the problem is (and worse since 2011 when they change piston manufactuers) is that the piston does not hold it shape or tolerances.. So, as it runs, the skirt begins to collapse, this "shrinkage" of the skirt allows for excessive piston thrusting (rocking) pressures when the piston STOPS at TDC and BDC. so, as time goes on, the clearance becomes more and more excessive and eventually the piston skirt will fracture and break OR it will fracture the cylinder skirt -->think of a pry bar (piston skirt) "prying" against the cylinder's lower skirt.. this is what is happening. eventually something gives.. sometimes it is the skirt of the piston, sometimes the cylinder skirt.. sometimes BOTH.. The result is always the same.. Catastophic failure.... and the engine is "hooped"

There are several ways to fix this.. We choose to use a VERY special designed piston that is lighter (less mass thrusting) , stronger (speaks for itself) and will hold its shape and tolernances (after 2000 miles or so our pistons will show only .0005" skirt collapse)

So, combining all 3 of these things that are inherent with the piston ,we use, and the risk of failure dimishes GREATLY!! In other wrlds.. take aways the excessive rocking and thrusting and the stress on the associated parts will always be less... We have been using this method for several years and the results are conclusive... The failures seem to be gone.

Some with try and have you believe that the cylinder is wearing.. This is nonsense.. Think of rubbing a piece of wood on a granite rock.. This is what you have with a piston and a NikaSil Plating.. NikaSil is near Diamond in its harness... It takes more than a light steel piston ring or aluminum piston body to wear a diamond.. In short.. the NikaSil is very hard and difficult to wear with a lesser hardness material.

If you are not seeing failures with your current riding group.. Consider yourself fortunate.. But , rest assured,, it WILL eventually happen.. Tell ya what.. pull down 1 of your engines and measure the piston.. (if you have over 1000 mountain miles) if the piston is still in spec, I will send you FREE pistons.. That is how sure I am on this..
Waiting for engine failure is not wise.. once it happens, it will be catastrophic and EXPENSIVE.

Compression checks tell you ZERO.. the issue is at the piston SKIRT not the ring area.. so, you will never get any indication of this using a compression check.

Hope this helps

 

[LUCKY 7]

thanks for the great information.

 

[recguy]

Great question

Here is what we have seen over the years with this engine (dating clear back to the 2008 IQ Chassis)

The pistons, when new, are properly sized... the problem is (and worse since 2011 when they change piston manufactuers) is that the piston does not hold it shape or tolerances.. So, as it runs, the skirt begins to collapse, this "shrinkage" of the skirt allows for excessive piston thrusting (rocking) pressures when the piston STOPS at TDC and BDC. so, as time goes on, the clearance becomes more and more excessive and eventually the piston skirt will fracture and break OR it will fracture the cylinder skirt -->think of a pry bar (piston skirt) "prying" against the cylinder's lower skirt.. this is what is happening. eventually something gives.. sometimes it is the skirt of the piston, sometimes the cylinder skirt.. sometimes BOTH.. The result is always the same.. Catastophic failure.... and the engine is "hooped"

There are several ways to fix this.. We choose to use a VERY special designed piston that is lighter (less mass thrusting) , stronger (speaks for itself) and will hold its shape and tolernances (after 2000 miles or so our pistons will show only .0005" skirt collapse)

So, combining all 3 of these things that are inherent with the piston ,we use, and the risk of failure dimishes GREATLY!! In other wrlds.. take aways the excessive rocking and thrusting and the stress on the associated parts will always be less... We have been using this method for several years and the results are conclusive... The failures seem to be gone.

Some with try and have you believe that the cylinder is wearing.. This is nonsense.. Think of rubbing a piece of wood on a granite rock.. This is what you have with a piston and a NikaSil Plating.. NikaSil is near Diamond in its harness... It takes more than a light steel piston ring or aluminum piston body to wear a diamond.. In short.. the NikaSil is very hard and difficult to wear with a lesser hardness material.

If you are not seeing failures with your current riding group.. Consider yourself fortunate.. But , rest assured,, it WILL eventually happen.. Tell ya what.. pull down 1 of your engines and measure the piston.. (if you have over 1000 mountain miles) if the piston is still in spec, I will send you FREE pistons.. That is how sure I am on this..
Waiting for engine failure is not wise.. once it happens, it will be catastrophic and EXPENSIVE.

Compression checks tell you ZERO.. the issue is at the piston SKIRT not the ring area.. so, you will never get any indication of this using a compression check.

Hope this helps

Yes, thanks. I will call my dealer and get some parts ordered. Sure hate to be stranded.

 

[neilsleder]

Good info!


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[E-Zmoke]

I have never really been sold on the rod ratio theory...but I would like it if you could please answer a couple questions.

Can you please explain the difference in detail between cast, and forged pistons? Why do some kits offer a cylinder shim, and longer pistons? Is this not just a "band aid"? What if one was to just match the piston to the cylinder? Wouldn't this be a highly more sufficient way to maximize performance, and life?

Thanks

 

[E-Zmoke]

Sorry I misread #3...thought it said all of the (cylinders) have failed after measuring them but it says "falled" (cylinders are within spec)

 

[E-Zmoke]

Also can you please explain are their any differences in the pistons from your drop in kit and the direct replacement kit? Or are they the same piston/design? Do you offer a turbo specific piston?

Thanks

 

[RK Tek]

I have never really been sold on the rod ratio theory...but I would like it if you could please answer a couple questions.

Can you please explain the difference in detail between cast, and forged pistons? Why do some kits offer a cylinder shim, and longer pistons? Is this not just a "band aid"? What if one was to just match the piston to the cylinder? Wouldn't this be a highly more sufficient way to maximize performance, and life?

Thanks

Cast Vs.. Forged.. Simply a different method of "forming" a part.. Forgings are stronger and usually lighter but are more expensive to produce.. this is the main reason why cast is used on most production vehicles... HOWEVER; there are more and more production autos beginning to use a forged piston... When a forged piston is designed properly and manufactured using proper techniques and alloys.. they will be a better part.. When they are NOT held to a higher standard (like some out there), then they CAN have some "quirks".

SAME with Cast.. Hence these "Chinese" made cast pistons that are out there.. Cheap to make but NOT held to the high standard in terms of alloy or production.. I gets calls every week from the people who saved $75.00 buying the cast chinese pistons ONLY to have this $75 savings turn into a HUGE loss when these pistons fail and ruin their engine.. Trust me on this one.. Don't roll the dice on the heart of your engine.. Spend the money and get the good pistons.. Same with Cranks... These Long Rod kits use a CHINESE rod (King Rod).. IMO, Chinese parts have no business in any high performance engine (or in North America for that matter.. but that is a whole 'nother topic)

Kinda like tires on yur street bike. you want to risk your life on KENDA tires doing 100 MPH down the road or spend a little extra and get a Bridgestone or Dunlop and KNOW that your riding on good tires...

Taller piston and shim.. I am not a fan of this mod AT ALL.. The piston lacks cylinder support at BDC and this is where the excessive thrusting forces are causing issues.. Raising cylinders REMOVES lower skirt support (which is already lacking), for this reason, alone, I am not a fan... The argument can be made that the added upper support negates the need for lower support.. I can see this but still do not like to see the piston NOT supported (even more than it already is ) via cylinder shimming...

 

[Gunnerthesnowman]

And your point is ?

 

[rmscustom]

Is the case volume on these motors lacking? Does your drop in kit change it?

 

[rmscustom]

Is there a benefit to installing a bypass on this motor and running it cooler? I was noticing a huge power loss last march in wet heavy snow and when I would look at the temp it was 140 plus but would drop as soon as I would let off the throttle and then the power would be back until the next temp spike.

 

[Ryeser]

Thanks for the info on this! There are a lot of us Poo guys that love the chassis and want to improve the reliability of the engine...

 

[0neoldfart]

I'm of the opinion that you get what you pay for, and frankly guys (and girls), the OEM sources parts through the least expensive manufacturer. Not likely that Polaris, Arctic Cat, etc is casting or forging thier pistons in-house. Cast pistons are commonly used in OEM build for a couple reasons: cost, and they are less likely to suffer a cold seizure due to the differences in thermal expansion rates (better for those who don't warm up thier sled properly). There is no chance in he!! you will find cast pistons in an automotive race engine, unless the builder was smoking something, but then again you won't find a full race engine in your daily driver - consider the horsepower vs. displacement between any newer sled motor and your daily driver, obviously the sled motor has a definitive advantage. Cylinder shims have been used sucessfully along with head modifications to raise port timing and maintaining compression on SOME engine designs (think 07-09 M8, although there are others).
In a nutshell, the consumer demands and EPA requirements dictate that the manufacturers produce cleaner two stokes, and someone has to pay for this technology. As consumers we are not prepared to spend 20K for a stock sled, so parts and manufacturing will be tendered out to the lowest bidder 99% of the time, which makes the end product less then stellar, and reliability is sacrificed. Not a bad deal for the OEM, as they are in business to sell snowmobiles, not fix them... just my humble opinion.

 

[trench]

Thanks for the info on this! There are a lot of us Poo guys that love the chassis and want to improve the reliability of the engine...

Hey Ryser I'm going to be putting one of these kits in my 2011, my engine feels like I have a paint mixer under the hood, don't really trust it anymore!

 

[Ryeser]

Chrisco can put it in locally if you need. He did mine, and it he did a great job at the time...

 

[gedakbx]

Chrisco can put it in locally if you need. He did mine, and it he did a great job at the time...

Hey ryeser did you do the complete drop in or just the pistons? How many miles on your set up what did you find for results?

thanks

 

[Ryeser]

When my engine went, it took out the entire top end... replaced top end, crank was still good. I went with the PMS kit at the time, as it was recommended to go with it... I would definitely go with RK if there is a next time, as they have nothing but the best from what I have heard in our group... Nothing wrong with my kit so far, I've been adding a little oil every run, letting it warm up, and I believe I now have close to 2,000 miles on it... since the rebuild. just went thru it a couple of weeks ago... pistons are still in good shape, had an issue with my TPS and exhaust valves, they are now fine. I will try to get one more season out of it.

There was a small increase in HP, and i also changed to V-Force reeds, so it was a little more peppy off the line than original...

 

[trench]

Thanks Ryser, going to tear it down myself and take it in to work and get the millrights there to make sure it all measures out to spec.