11 assualt piston study

peaceofwork · Dec 29, 2017

Over the years a buddy's sled has been eating pistons and a crank , I see it prefers to eat mag side more than cultch side Pistons but if it's really hungry it eats the mag one then gets started on the pto side. Shops have done it 3 times and last summer I give it a go thinking maybe the shops just we're not thurow and using due dillagence.
I pulled off the top end and did whatever I could think up to cure this, up to date my list looks like this...
New fuel filter
Tested fuel pressure
Had injectors serviced and tested
New fuel
Set TPS
Welded in and polished the divots in the y pipe
Ground out the high points in the exhaust ports
New reeds
New power valve diaphragms
-Cylinders renicasiled and fitted Pistons- clearances checked at fast enterprises and my regular local shop machinist
Very fine honing to finish the surface
Oil pump turned up
Oil added to fuel
Head and cylinder checked for warpage
Now a maybe a few hundred miles and the sleds running like crap and bits of aluminum visible on the electrode, I pulled it down and used muriatic acid to clean the aluminum off the cylinders and had a look around but I'm really struggling to cure this, it's not wet around the mag side crank seal and it's not showing codes but I must be missing something.
Now I think about replace the sock in the fuel tank on the pickup and I contemplate running the fuel pressure gadge while actually riding the machine .
Examining the Pistons it don't look like the ring ends butted at the locator pins and they did not push out 180 across on the cylinder, I don't see signs of detonation just melted skirt below the rings all the way around on the one piston, I say warm it up more before hitting to hard on the fuel but I am not sure exactly positively so I'm asking , maybe I can post a few pics of the Pistons for you piston whisperers.
If I had a blocked or semi blocked oil line in the crank case I guess I might have lost a crank bearing and rod bearing by now, I notice the y pipe looks oily looking down both ports so I tend to think it would look dry down their if their was an oil problem ?

peaceofwork · Dec 29, 2017

Vess gold and new Polaris gaskets each time , new in line oil filter and the pump arm gets held up to perge any air out of the line and pump.
My personal sled motor I built me and others that I built work just fine but this one is making me work.

Sheetmetalfab · Dec 29, 2017

After rebuilding 11 pro’s as a hobby.

Parting them out seems the best option.

peaceofwork · Dec 29, 2017

OUCH AND USUALY I LIKE YOUR HELP LOL,

pulltype_polaris · Dec 30, 2017

I have a 14 that went 3000 miles on stock pistons. Didn't look terrible when I changed them. Put forged new ones in. 500 miles later both intake sides wiped out and exhaust sides look new. Oiler turned up and a couple ounces added to fuel. Lots of oil in bottom end and in pipe. I'm stumped too. Not riding in a bunch of snow dust also.

volcano buster · Dec 30, 2017

I guess I'm curious why you changed to a different style of piston if the stock ones lasted 3000 miles.

kiliki · Dec 30, 2017

Sheetmetalfab said:
After rebuilding 11 pro’s as a hobby.

Parting them out seems the best option.

after as many rebuilds this is the answer^^^

tuneman · Dec 30, 2017

My dad's '13 Pro went down this week. Tearing it apart today to see what's up. It had a MTNTK kit in it too. Put it in at 6,600 miles. Sled has a bit over 9k miles now 8-D

Probably time to part it out.....

I do think a lot of issues are artificially created when folks put in new pistons. I can vouge for the improvement a forged piston makes in these sleds, but installing them is not a weekend garage mechanic job. It takes a good amount of technical skill to do it correctly and make it last.

peaceofwork · Dec 30, 2017

tuneman; Probably time to part it out..... I do think a lot of issues are artificially created when folks put in new pistons. I can vouge for the improvement a forged piston makes in these sleds said:
I do see what you and others are saying and I,ll tell you if the dealership can't make it run and last with Polaris Pistons or the mountaintek kit and head, I don't mind giving it a go because in the end the professionals couldn't do it .
I built my 12 pro motor and it's just fine and many other motors are living a long life.
I do clean work as in follow torquing patterns and specs and get their in stages gap rings proper with a light coat of oil on all the moving parts using new Polaris gaskets and for piston to cylinder clearance I have 2 shops check that for me.
I bleed the air out of the cooling system and I see coolant moving in the resavor bottle and the temp has stayed so very close to the temps of the other 800 pro's in our riding group and it don't loose coolant.
Now that it's once again back together I'm thinking about a leek down test and or pressure testing this build before it gets a snow day . I'm unsure about a couple of things like will the power valves bleed off air pressure ? Will grease seal the pv enough to hold 10 lbs pressure ?Should I aim to test both sides at once or one side at a time?
Is their any one here that tests their new built cfi 800 for leek down? I'd sure appreciate a rundown on the specific cfi procedure.

Sheetmetalfab · Dec 30, 2017

Don’t get me wrong.

A 12 or newer is worth rebuilding.

Part out the 11’s though............

LoudHandle · Dec 30, 2017

INDY SPECIALTIES is the only place I will send my cylinders, and why!

IMO; Nicasil Cylinders should NOT be honed at all (as most people can not invest in the proper honing shoes / machine to do it correctly). When the average joe attempts to hone it they use the incorrect hone and inflict far more damage to the cylinder than just putting new (Stock) pistons in it. The only machine I'm aware of on the North American Continent with a tried and true Nicasil honing setup is Indy Specialties.

If there is any visible cross hatch it is not smooth enough (much less if you can feel it) to not wipe out the rings and pistons. You can NOT / should NOT apply old school cast iron and automotive experience to Nicasil cylinders. It will not agree with what has been learned in the last few years about Nicasil and how to get better than 4 stroke reliability.

When you do it correctly (read; Indy Specialties) you will never need to touch the top end again, ever, period! Well maybe after 10-15 thousand miles, but who keeps their sled that long?

Forged pistons are another fairy tale, which some still believe apparently, but due to their metallurgical differences. Will always four corner seize at some point. regardless of how generous you are with your clearances.

Norway · Dec 31, 2017

LoudHandle said:
IMO; Nicasil Cylinders should NOT be honed at all (as most people can not invest in the proper honing shoes / machine to do it correctly). When the average joe attempts to hone it they use the incorrect hone and inflict far more damage to the cylinder than just putting new (Stock) pistons in it. The only machine I'm aware of on the North American Continent with a tried and true Nicasil honing setup is Indy Specialties.

If there is any visible cross hatch it is not smooth enough (much less if you can feel it) to not wipe out the rings and pistons. You can NOT / should NOT apply old school cast iron and automotive experience to Nicasil cylinders. It will not agree with what has been learned in the last few years about Nicasil and how to get better than 4 stroke reliability.

When you do it correctly (read; Indy Specialties) you will never need to touch the top end again, ever, period! Well maybe after 10-15 thousand miles, but who keeps their sled that long?

Forged pistons are another fairy tale, which some still believe apparently, but due to their metallurgical differences. Will always four corner seize at some point. regardless of how generous you are with your clearances.

I have huge respect for Dans skills, experience and the resulting process he puts in finishing his cylinders (and other Products), but I dare say this goes beyond that..

Remember the 1996 F III from Doo came With the mindblowing News of Nicasil, and we've been running them since. Huge numbers of people have acid-cleaned and then ball-honed nicasil cylinders without problems.
Along comes CFI-2 and -4 engines.. WTF happened??

Not saying I can school people in honing or nicasil, but I just don't buy that. Sorry.

On this particular engine, I have a memory ringing of crank indexing.. has that been checked? To much ignition and a bit out of phase = taking mag side first.
Second; I just had to work my a$$ of to get air out of my oil line! I thought it was gone, then flipped the sled on its left side and waited... There it was! Bubble came creeping put again.
Had to disconnect the oil hose and let oil spill (on rags) from oil tank and on top of the hose before quickly putting it in again. Didn't dare trust any other method..

Sounds tricky tho, good luck!

kiliki · Dec 31, 2017

don't forget about some of the oil caps not venting.:face-icon-small-blu

peaceofwork · Dec 31, 2017

Thanks for the ideas guys
Crank indexing is a very interesting thought so now I'm thinking could it be checked while still in the machine? Degree wheel on the crank and dial indicators on the piston tops through the spark plug holes? Sounds sketchy to me but because the crankshaft don't have a lot of miles on it I'm hesitant to pull the motor.

geo · Dec 31, 2017

First thing I check with a forged piston seizure (if you lost aluminum you had a seizure with multiple possible reasons) on a Pro is a cracked cylinder (along the length of the back boost port). Find the same thing with Cats and dirt bikes with a forged piston seizure but it is the exhaust boost port bridges that crack.
Amazing mount of friction and force is created when things don't expand at the same rate and plenty of torque to push it through.

If you have a "weird one" lol, I think Norway was setting you on the right path with checking the crank phasing (if all else is truly well). Sleds have been twisting cranks since they put a 10 lb weight on one end.
Thing is, port injection has zero "forgiveness" compared to throttle body injection or carbs.

peaceofwork · Dec 31, 2017

Geo , I cleaned the aluminum off the nicasill cylinder with muriatic acid so if I had a crack through the plating any place the acid would boil up showing a crack if their was one, not only that but looked it over with a magnifing glass.
At this point the sled is back together with new Pistons and gaskets and has been heat cycled. I think of fixing this machine rather than just replace parts so ya I like the idea of crank phasing and a leek down test before getting it out for a ride.
How come your not out riding today after the big dump of snow all across southern bc? Do you go up to honeymoon?

Merlin · Jan 1, 2018

Can you clarify that a bit?

Do these shops measure the PTCW clearance & simply provide you with the measurements OR do they measure & tell you that you're good to go based on their judgement?

peaceofwork said:
for piston to cylinder clearance I have 2 shops check that for me.

diamonddave · Jan 1, 2018

Sheetmetalfab said:
After rebuilding 11 pro’s as a hobby.

Parting them out seems the best option.

Totally Agree. 11's should all be updated to 2012 or newer.

As for getting to the bottom of the repeat failures, more detailed info would be nice.

I would not waste my time with 2011 injectors. Throw those in the trash. Get some 2012's and reflash the ECU.

I would go into the fuel pump (2011's were problematic), install a permanent fuel pressure gauge.

Pull the motor and perform a leakdown test.

Where'd the crank come from? What kind of pistons are you running now?

Exhaust Porting? More info on what was done? Maybe time for a new monoblock.

And I would be replacing oil line check valves. Cheap compared to R&R'ing and throwing pistons and your time in it repeatedly.

Now you see why many of believe the 2011 should go to the wrecking yard.

peaceofwork · Jan 1, 2018

Merlin said:
Can you clarify that a bit?

Do these shops measure the PTCW clearance & simply provide you with the measurements OR do they measure & tell you that you're good to go based on their judgement?

Off the top of my head I seem to remember the box the Pistons come in said a little less than five thousands 4995 if I recall right. Also for ring gap it specked four thou per inch of bore minimum and I seem to remember
3.35" /85mm eighteen thousands ring gap is what I went with.
The shop that did the renicasiling job had the Pistons before the process began, I mailed the stuff half way across the continent to be serviced so was not their to whitness their measurements but was assured it was at specs. Now after shipping back home I took the monoblock and the piston my local machinist and watched it all get measured out a few times . I know that it's all at least at the minimum spec to a little less than five thousands ptcw

peaceofwork · Jan 1, 2018

diamonddave said:
Totally Agree. 11's should all be updated to 2012 or newer.

As for getting to the bottom of the repeat failures, more detailed info would be nice.--- ok Dave you got it

I would not waste my time with 2011 injectors. Throw those in the trash. Get some 2012's and reflash the ECU.--- I had the injectors serviced and tested, flow rated before I ever heard you say don't even mess around with them old things you would just upgrade to new injectors an reflash.

I would go into the fuel pump (2011's were problematic), install a permanent fuel pressure gauge. --- I did buy a test gauge and found I had 58/60 lbs pressure while running and when I shut down the machine it it dropped 10 lbs in ten min then held steady for hrs. I was contemplating drilling a little hole in the shroud so I could run my gauge on the machine at high rpm to see if it maintained 60ish lbs pressure under load. Again it's not my sled and I live 2hr drive from the snow

Pull the motor and perform a leakdown test.--- I been asking on here if someone could give me the rundown on how to do or what I need to know about doing a leek down test on a cfi motor. I built my own leek down tester fo my cr500 testing but I am unsure about doing the twin cylinder cfi motor.

Where'd the crank come from? What kind of pistons are you running now?---the crank come from a Polaris dealership I assume new Polaris? 3 days ago I threw in asset of Weisco Pistons and new gaskets and started asking about on here how to do a leek down test and for helpful ideas.

Exhaust Porting? --- no exhaust porting, I gently knocked off the casting slag, high spot off the bottom of one port and smoothed sharp edges around a pock mark. More info on what was done? Maybe time for a new monoblock.--- could be but it may have 300 miles on it from when I had it redone last summer.

And I would be replacing oil line check valves. Cheap compared to R&R'ing and throwing pistons and your time in it repeatedly. ---New updated oil pump last winter at the dealership 400 bucks I don't know abou the check valves but I can say the y pipe is oily wet when I look down it, also it's oily wet inside the crank case when I look after lifting the monoblock . Because of these things I assume all is well Concerning oil delivery and I have turned up the oil.
I did the top end this last fall and 3 days ago but I'm asking questions before it sees a snow day all the other builds or parts swaping was done at the dealership.
My friend thought the dealers builds wouldn't last so maybe I could figure it out, I am the guy that tested injectors, replaced fuel filter, removed the pull start looking for an oily mess around the mag side seal, fixed up potential hotspots on the exhaust side. This sled has close to 2000 miles on it and a few nice extras so it would be nice to figure it out

Now you see why many of believe the 2011 should go to the wrecking yard.

Theirs my best answers Dave, what's up with 12 injectors and a reflash? I thought the 2011 models were notoriously rich and that's why the vforce reads had a lot of trouble in the 11 poo ?

11 assualt piston study

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