With the Polaris CFI Engine (ALL 2 Injector Models,Including the HO (AXYS)), the lower half of the engine is dry.. meaning there is little to no fuel entering there.
FUEL (NOT COOLANT) is the #1 cooling agent for ANY Engine (important to remember) and this engine has none!
Heat is one of the primary causes of skirt collapse and skirt collapse is ONE of the primary issues with the OEM design..
Remember this, VERY IMPORTANT, a compression check will tell you little to nothing about the health of your skirts.
You can have a BROKEN off lower skirt and the compression reading will not change!
Doing a compression check will not yield any relevant information regarding the health of your PISTON SKIRTS.
People always state "I pulled my OEM pistons and they LOOKED fine and compression reading was still in spec!"
LOOKING fine and MEASURING fine are 2 VERY different things!
You MUST MEASURE the piston in order to determine if the piston is "GOOD".
Skirt collapse happens usually WITHOUT any scoring or visual appearances on the piston. In other words.. your piston can LOOK perfect but MEASURE out of spec.
Our CUSTOM pistons (Direct replacement, Drop In, AND Big Bore) are CUSTOM designed!
They have very a proprietary design that is unique to ALL of our pistons.
These pistons, we offer, are FAR from ANY "off the shelf" OR "aftermarket" piston available today!
They are 100% unique to RK TEK!
They are also lighter than the OEM Piston and that will help with the acceleration from a stop.
Another VERY important misconception... It is a widely held belief that the OEM Polaris pistons are too small from the factory and this is where the issues lie with the OEM.
The OEM Polaris piston is 100% in spec and the proper size when new in the box!
The REAL issue is that the OEM piston does not REMAIN in spec after use.
The other major issue is the LACK of lower piston support at BDC.
We address this with our REV 2 Drop In Kit.
We are the ONLY company that has a kit to aid in lower piston skirt support.
When you hear that all these aftermarket kits have a tighter tolerance than the OEM.. it is simply NOT true!
The truth is that the OEM piston's tolerances are in spec, they just don't stay there.
Our custom pistons HOLD their tolerances.. AGAIN.. Visual inspection will tell you NOTHING about the size of your piston.
The piston kits we offer (some call a fix kit.. we do not) are the highest quality piston on the market today.. They are designed with hard anodizing on the ring lands, pin boss and crown underside AND custom coating on the crown.
Installation of ANY of our pistons will allow ANY Polaris CFI engine to reach a higher potential. THESE pistons address many issues associated with the OEM design (Balance, weight, ring location to name a few)..
Turbos also love them!
"FIX KITS" Or other "Clever" marketed named Kits
These are very clever marketing terms to impose the "idea" that by installing these kits that the engine is "fixed" and will no longer be prone to failure.
This can be very misleading!
The TRUTH of the matter is that MOST of these "Fix Kits" are nothing more than an Arctic Cat 800 Piston under a different name.
If it uses a 1/4" shim under it, then this is most likely the case. Sorry guys... this is the reality!
Some will also have you believe that they have installed a "special" pin offset. The truth is that the Factory OEM Piston has a .020" offset to help relieve thrust pressure near Bottom Dead Center (BDC).
One would hope that any of these other pistons would also contain this same OEM offset. Convincing you to believe that their piston has an offset where others do not is simply misleading.
Let's get a little more specific:
1) The 2008-2012 Pro 800 CFI Engines use a crank manufactured by MAPE. This MAPE crank has a high failure rate of the lower rod bearing and the outer bearings.
The MAPE crank was discontinued in 2013 and newer engines in favor of a new manufactured crank by FUJI. This FUJI crank is a superior crank to the MAPE in every way.
This FUJI crank WILL install without any modification into any 2008-2017 engine case. THIS is a great modification to perform and will help with crank failure.
Clever named kits do not address the MAPE Crank Issues!
2) The 2008-2009 CFI-4 engines had a VERY thin lower cylinder skirt that was prone to cracking especially once the OEM piston gets lose in the bore.
In 2010 Polaris thickened up this skirt. Polaris thickened up the skirt, again, for 2011-12 CFI-2 Engines.
ALL of the 2008-2012 800 Engines were prone to lower cylinder skirt cracking!
Installing ANY clever named piston kit will NOT fix your thin walled cylinder skirts!
3) For 2013-Present (HO included), Polaris thickened up the cylinder intake skirt, once again, to help alleviate all the cylinder skirt failures.
This thicker skirted cylinder WILL install into your 2011-2012 cases ONLY if you modify the upper case half to accept the thicker skirt. This is a great modification and can be done by any competent machine shop. This allows your 2011-2012 engines to run with the better 2013 cylinder.
4) There is a common belief that the 2013 and newer engines have a cylinder or crankshaft offset compared to the earlier years. This is 100% false!!
5) It is also believed that there exists a Rod-Ratio issue with the Polaris 800CFI engines. More clearly, the rod ratio is too small for this engine.
The Rod-Ratio is the ratio of the rod length to the stroke of the engine. The longer the rod, the higher the ratio, given the same stroke.
The Polaris rod is approx 132mm in length and the stroke is 70mm yielding a rod-ratio of approx 1.88.
The Arctic Cat 800 has the approx 130mm Rod and the same stroke. Therefore, the rod ratio on the Arctic Cat 800 engine is WORSE than that of the Polaris 800 engine.
The Ski Doo 800HO and 800R engines have a 132mm rod and 75.7mm stroke yielding a rod-ratio of 1.74.
So, it stands to reason that IF the rod-ratio of the Polaris 800 CFI engine is too small, then the rod-ratio of the Arctic Cat and Ski Doo 800 engines are also too small (especially the Ski Doo since it is even smaller).
Based on these FACTS, I think it is safe to assume that the rod-ratio is not an issue and claiming that is nothing more than a scare tactic.
You can derive your own conclusions.
6) ANY running of the thinner walled cylinders (2008-2012) can lead to stress and fatigue on the cylinder skirts. This stress is amplified by a looser piston and the potential for full cylinder skirt failure increases when a piston is out of tolerance .
Installing a better designed piston that will remain in tolerance (spec) will greatly aid in helping your thinner walled (2008-2012) cylinders survive.
Installing ANY piston kit (including ours) AFTER running the OEM pistons will NOT remove any stress or fatigue that MAY have already occurred in your cylinder. In other words, IF your cylinder is fatigued, it will STILL be fatigued once a better piston is installed.
7) Another held belief is that the new AXYS piston has addressed the OEM short-comings mentioned above.
The new AXYS piston is basically, the SAME piston with some added oil retention grooves on the exhaust upper skirt. This is not a bad change but does very little to aid with the skirt collapse, extreme piston weight, and heavy ring drag.
We feel this piston to be mildly superior to the previous piston but also feel it is a lesser quality piston than what we offer.
It has EXCESSIVE skirt taper.. This allows for a lot of rocking in the bore (not good)
It also is VERY heavy!
Running our piston vs. this piston WILL show some performance enhancements.
600 Polaris Pistons
1) The 600 Polaris Engine is a great engine!.. However, the piston design is not much better than the 800 Piston.
It suffers from skirt collapse and it is also WAY too HEAVY!
There are some massive gains to be had by drastically altering the piston design.
We have spent the time and developed a Piston Kit and a Drop In Piston/Head kit for the 600 Twin..
Both of these kits offer SIGNIFICANT performance enhancement and extend engine life!
Hopefully, this article will clear up some of the mis-conceptions that surround this engine and its internal design?