Pistons?

Summitstef · Apr 1, 2015

Now that the sled is finally back from the stealership, I'm thinking that a fresh top end is in order.
I'm not exactly sure what pistons to use but I know that I'm staying away from RK Tek and Wiseco.

Was thinking OEM or SPI. Any suggestions? What really would be ideal is a set of grooved OEM Polaris 2016 pistons, but did the bore size change on the new 800CFI HO engine?

Jkmola · Apr 2, 2015

I'm acutally gonna redo my top end this summer as well. Rk Tek pistons are the way I'm leaning right now. Why are you against them?

powderseeker7 · Apr 2, 2015

Summitstef said:
What really would be ideal is a set of grooved OEM Polaris 2016 pistons, but did the bore size change on the new 800CFI HO engine?

I would really like to know this as well. I am considering a new top end in the off season.

tuneman · Apr 2, 2015

I'll be looking my 2012 over this summer to determine if it needs new pistons. If so, thru my fairly extensive research, I'm leaning toward the Bikeman Durability Kit. I like the fact that they offset the wrist pin, since we know 2012 engines have thin cylinder skirts. They also claim a slight increase in HP, which makes sense to me with their design. They're the only ones that I've seen that actually get into specifics:

1. Wossner Pistons - Unmatched forged piston quality compared to any other manufacturer. Other companies use Wossner but they are not the same design as ours.
2. We engineered our Pistons .250" taller than stock to reduce fatigue on piston skirts due to rod angles. Some people install longer rods but doing so decreases power and costs much more.
3. We designed Gas Ports into our piston These are small ports that allow oil film from underside of piston through the piston to help lubricate high load areas.
4. We offset our wrist pin .020" towards the exhaust side to reduce skirt loading during power stroke.
5. We engineered a wider ringland between the rings to reduce ring temperature.
6. The addition of the .250 inch spacer under cylinder corrects cylinder volume for the 800 cfi resulting in more efficient power.
7. The addition of the spacer under cylinder also lifts cylinder intake shirts up out of the reed window reducing intake restriction and resulting in more power during high airflow demand at high RPM.

Jaynelson · Apr 2, 2015

I have never owned anything from Bikeman - but I will say that I really appreciate the detail they go out in to with the specs (as above), dyno tests, etc.

Carls Cycle · Apr 2, 2015

It is the same bore, as the base gasket is the same as the 2015 motor. To answer your question, the 16 pistons will fit in the Pro 800 motor, but since the piston from 14 and 15 will fit and work properly, why not use those pistons. Those pistons have been pretty near indestructible, and motor reliability due to proper clearances and better skirts, along with the thicker walls on the newer cylinders have made these motors really reliable. Don't mess with the supposed "fix kits" would be my recommendation. Always better to go OEM, since they are actually designed for the sled.

Besides, if you are going to go with the 16 pistons, I would get the whole rest of the sled to match it. YOU won't regret it!

powderseeker7 · Apr 2, 2015

Carls Cycle said:
It is the same bore, as the base gasket is the same as the 2015 motor. To answer your question, the 16 pistons will fit in the Pro 800 motor, but since the piston from 14 and 15 will fit and work properly, why not use those pistons. Those pistons have been pretty near indestructible, and motor reliability due to proper clearances and better skirts, along with the thicker walls on the newer cylinders have made these motors really reliable. Don't mess with the supposed "fix kits" would be my recommendation. Always better to go OEM, since they are actually designed for the sled.

Besides, if you are going to go with the 16 pistons, I would get the whole rest of the sled to match it. YOU won't regret it!

I just checked the Polaris parts fiche and they have the '13 piston part number changed to the '14/'15 piston pat number.
I'm leaning towards these OEM pistons.

On a related note, seems the 600 CFI can fit in the AXYS chassis does that mean the 800 will fit? In turn will the new 800 HO fit in the Pro?

Reg2view · Apr 2, 2015

Carls Cycle said:
... but since the piston from 14 and 15 will fit and work properly, why not use those pistons. Those pistons have been pretty near indestructible, and motor reliability due to proper clearances and better skirts, along with the thicker walls on the newer cylinders have made these motors really reliable.

I realize that it would be very politically incorrect for you to express your honest opinion - but I gotta ask for the rest of us - why did it take over THREE FREAK'IN YEARS for poo to address the CFI2 piston and cylinder issues?

God bless CFI4 owners.

FWIW, I've had excellent luck with the RKT Wossner's in a dropin kit with head (first of the Wossner piston designs for the 800). The Carl's clutching, evol R kits, and other stuff from Carl's were excellent, too. And I'm not sucking up just to get a honest answer. No experience with the BM kit.

alwaysright · Apr 3, 2015

Carls Cycle said:
It is the same bore, as the base gasket is the same as the 2015 motor. To answer your question, the 16 pistons will fit in the Pro 800 motor, but since the piston from 14 and 15 will fit and work properly, why not use those pistons. Those pistons have been pretty near indestructible, and motor reliability due to proper clearances and better skirts, along with the thicker walls on the newer cylinders have made these motors really reliable. Don't mess with the supposed "fix kits" would be my recommendation. Always better to go OEM, since they are actually designed for the sled.

Besides, if you are going to go with the 16 pistons, I would get the whole rest of the sled to match it. YOU won't regret it!

I too asked this question a while back, glad to have carl's confirm they will fit, thanks!

Do we have a motor builder that is saying the stock motor is reliable? That's a first and thank you for doing so. I just got a '13 800 sb pro-r and have really been on the fence about replacing the mine with 3400 (albeit flatlander) miles.

I come to this board for good info and this is exactly what I want to hear, not just another company trying to sell parts. although I don't have the '14-15 pistons I now more than ever feel like I can ride it without too much to worry about. I'll check ring land and piston skirts and hope to ride it more with the stockers still in it.

I too think the '16 pistons are an improvement and have only heard on 1 of these motors going down here on the interwebz so who knows.

Either way, carl's has just confirmed what I've been thinking all along, polaris has made these motors reliable, not something any of the other motor builders/parts slingers would have you believe

tuneman · Apr 3, 2015

Reg2view said:
I gotta ask for the rest of us - why did it take over THREE FREAK'IN YEARS for poo to address the CFI2 piston and cylinder issues?

I actually think they've addressed the situation well. The internet has just blown it up into a way bigger deal that it really is.

I totally respect the response from Carls Cycle. However, can I get your feedback on what to do about a 2012 engine that has the thinner cylinder skirts? Will just new pistons take care of the issue? Or would it be even better to widen the rings, offset the wrist pin and increase the height in order to reduce cylinder skirt fatigue. I'm certain the new OEM pistons are better than the old ones, but I want more than just a marginal improvement.

Also, if BM's claim of a HP increase is true, why wouldn't I want to get that kit for the increased performance, especially if it costs nearly the same as two new OEM pistons?

Carls Cycle · Apr 3, 2015

The proper way to fix a 2012 motor is to actually update the cylinders as well. The newer cylinders have twice the thickness of the earlier versions as well as better tolerances, so they hold up better. Downside is the monoblock is about 1100 dollars. Plus, you have to machine your upper crankcase to take the new cylinders. That cost's about 125 to do. Most people don't understandably want to drop that kind of money, plus the 500 dollars or so for the pistons and gaskets, so they go with one of the supposed fix kits.

P.S. by the way, we do the machining, and I even think we have a reconditioned set of cylinders that will fit a 2013-15 that we are selling for 600. Plus, we have all the pistons and gaskets necessary for the complete rebuild. When I get back to work tomorrow, I can check on that set of cylinders if you are interested.

Reg2view · Apr 3, 2015

tuneman said:
I actually think they've addressed the situation well. The internet has just blown it up into a way bigger deal that it really is.

FWIW, I ride with a poo dealer and two of his techs. Their experience is hands on, and the internet rep on untouched 11-12 motors is pretty close to their reality. 13+ is a better story. They don't all go down in 1500 miles, but too many did. More oil, good warmups before hammering, anytime you restart, and luck of the draw all helped.

gtwitch · Apr 5, 2015

Great comments on Piston selections! Lots of opinions here and all are probably valid! My thoughts after talking with different rebuilders are as follows and worth just what I charge here. As one rebuilder that has a steller reputation says, Polaris pistons are good and usually run 2k to 3k miles and they are cast pistons that handle the temp cycling usually better than forged pistons and this comment has come from two other rebuilders. If you do put in forged pistons, make sure that you be judicious about the warmup procedures every time you start it from cold or from a warm shutdown and then a start up from that where a cold slug of water from the coolers could cold shock. Been through 1 set of forged pistons (Wiseco) replacement this season on a 09 D800 and failure at 211 miles after discovering that the Exhaust Gilloutines were contacting the pistons (more common than you would think) origionally I thought cold seize here but not the case. I have since programmed my CNC mill and built a jig to radius mill these exhaust gilloutines back away from the piston faces on an upper cyl rebuild. I have gone back to using the cast pistons as my choice on upper end rebuild or complete remans only because of the temperature stability of cast pistons, not saying that the forged pistons are all bad, because they are not if warmup protocall is followed! See if you can get your customers to do this, good luck!

gtwitch in wyoming

Merlin · Apr 5, 2015

gtwitch said:
Great comments on Piston selections! Lots of opinions here and all are probably valid! My thoughts after talking with different rebuilders are as follows and worth just what I charge here. As one rebuilder that has a steller reputation says, Polaris pistons are good and usually run 2k to 3k miles and they are cast pistons that handle the temp cycling usually better than forged pistons and this comment has come from two other rebuilders. If you do put in forged pistons, make sure that you be judicious about the warmup procedures every time you start it from cold or from a warm shutdown and then a start up from that where a cold slug of water from the coolers could cold shock. Been through 1 set of forged pistons (Wiseco) replacement this season on a 09 D800 and failure at 211 miles after discovering that the Exhaust Gilloutines were contacting the pistons (more common than you would think) origionally I thought cold seize here but not the case. I have since programmed my CNC mill and built a jig to radius mill these exhaust gilloutines back away from the piston faces on an upper cyl rebuild. I have gone back to using the cast pistons as my choice on upper end rebuild or complete remans only because of the temperature stability of cast pistons, not saying that the forged pistons are all bad, because they are not if warmup protocall is followed! See if you can get your customers to do this, good luck!

gtwitch in wyoming

That is all good info. & I agree with your preference in cast over forged however it seems that very few people understand that the key to success of running any of these pistons, cast or otherwise, is proper blue printing during assy.

If you measure the clearances but don't take the time to have the cylinders properly fit to the specs. of the piston being installed, thinking "what's a thousandth of an inch either way?", don't expect great results.

While proper warm - up is absolutely essential, it won't make up for improper PTCW clearance.

gtwitch · Apr 6, 2015

I agree with the blueprinting and checking all available information about the fitment of all parts and I done this since I started building race engines and others in the early 70s . It never has been a waste of time and I feel it has paid off in every respect. Will finish an 11 PRO today but probably not get it on the snow for a breakin till next Nov but I can always hope for a late season DUMP!!

gtwitch in wyoming

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