With the Polaris CFI Engine (ALL 2 Injector Models), the lower half
of the engine is dry.. meaning there is little to no fuel entering
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!
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
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
They have very a proprietary design that is unique to ALL of our
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 poor manufacturing of this OEM piston and dry lower end
design allow this piston to quickly get out of spec.
The other major issue is the LACK of lower piston support at
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
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.. Can't say that for many
of the other kits. 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!
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
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.
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
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
Installing a better piston (from anybody) will NOT FIX your crank
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 poor quality
OEM piston got 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
3) For 2013-Present, Polaris thickened up the cylinder intake
skirt, once again, to help alleviate all the cylinder skirt
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.
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
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
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
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 (OEM
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
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.
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
Both of these kits
offer SIGNIFICANT performance enhancement and extend engine life!
You can read up on
these more here:
Hopefully, this article
will clear up some of the mis-conceptions that surround this engine
and its internal design?