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Oh No! Another Pro Burn Down Thread – Sorry

diamonddave

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I have not had much luck with the mtntk kit on 2013 and up Pro's. We went back to OEM pistons and have not looked back.. I do agree that you should check for seal, fuel filter, or possible injector issue but I have had a couple poo 800's melt down after doing a mtntk install just to freshen up the top end. Both with under 500 miles on them.
Indy Dan has a good write up on poo 800 pistons in Polaris section on this forum. Well worth the read.
Good luck with rebuild.


I have installed over 35 MTNTK Fix kits without one comeback, failure, or runnability issue. The fix kit was not the issue with RMK900Tractor's motor failure. 3 seasons, 1,500 miles and an issue at -34*F. Something else caused this problem. I'll bet fuel injectors, crank seals, or some other fuel starvation issue.

At this time, I currently have an industry leading Polaris motor shops engine in my garage. Story is it has less than 100 miles and both the cylinder skirts have cracked and a "piston" skirt broke off and went through the bottom of the case. Pieces have filled the rod bearing so it needs a crank also. Worse one I have ever seen.

As for your comment about the MTNTK fix kit being the problem here.....There are inherent issues with this motor design, electronics, controls, and mapping strategy that require a lot more attention to the outside of the motor to make them live.

1) These motors are very temperamental to fuel injector issues and oil cap venting. I have been preaching about the lack of venting from the stock cap since the Dragon days and was told I was crazy here on the forum.

2) I've also been touting everyone on getting injectors ultrasonic cleaned and flow tested during rebuild's the last few years. Injector placement on this motor leads to carbon build which then messes up the fuel flow. BRP learned this a long time ago and scrapped the SDI. Since these motors run so lean with stock mapping (especially '13's) they cannot handle anything less then ideal conditions, fuel flow, quality fuel, perfect TPS settings, proper storage and use. I have been having injectors cleaned and flow tested in previous years however, I am beginning to see injector fault codes also prior to engine failure's which indicates an electrical problem with the injectors as well as the carbon build up issue. Ultrasonic cleaning and flow testing an injector with an electrical fault is useless.

Take a partially plugged fuel injector causing a fuel flow pattern issue in a transfer port, a less than ideal fuel filter micron media that allows for reduced volume but with good fuel pressure, and you have a recipe for disaster with a lean mapped motor.

Then take less than ideal TPS settings, lean mapping, oil vent issues, crank seals that seem to be failing at early intervals, a noisy electrical system (that's a whole other discussion), along with what I have described above and you'll see that the 600/800 CFI-2 is a very temperamental motor to keep from having an engine failure. I'm not saying it can't be done but the struggle of challenges is real and attention to the details outside the motor is a must.


Early this year I started replacing injectors on all top ends and motor rebuilds with mileage near 1,500 miles instead of ultrasonic cleaning and flow testing. $260 from Polaris for injectors is cheap compared to the heart ache of a comeback or a heli ride and a burndown.


Hmmm.
 

Snowmow

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I have installed over 35 MTNTK Fix kits without one comeback, failure, or runnability issue. The fix kit was not the issue with RMK900Tractor's motor failure. 3 seasons, 1,500 miles and an issue at -34*F. Something else caused this problem. I'll bet fuel injectors, crank seals, or some other fuel starvation issue.



At this time, I currently have an industry leading Polaris motor shops engine in my garage. Story is it has less than 100 miles and both the cylinder skirts have cracked and a "piston" skirt broke off and went through the bottom of the case. Pieces have filled the rod bearing so it needs a crank also. Worse one I have ever seen.



As for your comment about the MTNTK fix kit being the problem here.....There are inherent issues with this motor design, electronics, controls, and mapping strategy that require a lot more attention to the outside of the motor to make them live.



1) These motors are very temperamental to fuel injector issues and oil cap venting. I have been preaching about the lack of venting from the stock cap since the Dragon days and was told I was crazy here on the forum.



2) I've also been touting everyone on getting injectors ultrasonic cleaned and flow tested during rebuild's the last few years. Injector placement on this motor leads to carbon build which then messes up the fuel flow. BRP learned this a long time ago and scrapped the SDI. Since these motors run so lean with stock mapping (especially '13's) they cannot handle anything less then ideal conditions, fuel flow, quality fuel, perfect TPS settings, proper storage and use. I have been having injectors cleaned and flow tested in previous years however, I am beginning to see injector fault codes also prior to engine failure's which indicates an electrical problem with the injectors as well as the carbon build up issue. Ultrasonic cleaning and flow testing an injector with an electrical fault is useless.



Take a partially plugged fuel injector causing a fuel flow pattern issue in a transfer port, a less than ideal fuel filter micron media that allows for reduced volume but with good fuel pressure, and you have a recipe for disaster with a lean mapped motor.



Then take less than ideal TPS settings, lean mapping, oil vent issues, crank seals that seem to be failing at early intervals, a noisy electrical system (that's a whole other discussion), along with what I have described above and you'll see that the 600/800 CFI-2 is a very temperamental motor to keep from having an engine failure. I'm not saying it can't be done but the struggle of challenges is real and attention to the details outside the motor is a must.





Early this year I started replacing injectors on all top ends and motor rebuilds with mileage near 1,500 miles instead of ultrasonic cleaning and flow testing. $260 from Polaris for injectors is cheap compared to the heart ache of a comeback or a heli ride and a burndown.





Hmmm.



All very valid points! I also wonder how many mountain guys go with a high compression head when they do a top end or other means of adding a few HP. All Adding insult to injury to an already aging/failing electrical/fuel system or weak crank seals.

Like you’ve said. So many things go into keeping these machine running strong.

People have been dooped into thinking a “FIX IT KIT” is a end all be all solution to durability issues with these motors. Not the case guys!
 

diamonddave

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All very valid points! I also wonder how many mountain guys go with a high compression head when they do a top end or other means of adding a few HP. All Adding insult to injury to an already aging/failing electrical/fuel system or weak crank seals.

Like you’ve said. So many things go into keeping these machine running strong.

People have been dooped into thinking a “FIX IT KIT” is a end all be all solution to durability issues with these motors. Not the case guys!



Yep, very good point.

The MTNTK kit does decrease the squish just a hair, (I've seen about a 0.003" - 0.005" decrease over stock). Adding a higher compression head on top of that without verifying squish and now we may have a new problem and then the kit gets blamed.

With the stock head, there's no problem.

There's only one Fix Kit. The MTNTK Fix kit. I have not used anything else.


https://www.mtntkperformance.com/engine-performance/performance-kit-0
 

RMK900Tractor

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They won’t vent properly at the 45ish degree angle they are at. Take a paper clip and heat it up red hot, then poke a hole or two (red arrows)for better venting. If it’s upside down for an extended period u might get a couple drips, nothing to worry about though

Thank you for the suggestion, will do.
 

RMK900Tractor

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I have installed over 35 MTNTK Fix kits without one comeback, failure, or runnability issue. The fix kit was not the issue with RMK900Tractor's motor failure. 3 seasons, 1,500 miles and an issue at -34*F. Something else caused this problem. I'll bet fuel injectors, crank seals, or some other fuel starvation issue.

At this time, I currently have an industry leading Polaris motor shops engine in my garage. Story is it has less than 100 miles and both the cylinder skirts have cracked and a "piston" skirt broke off and went through the bottom of the case. Pieces have filled the rod bearing so it needs a crank also. Worse one I have ever seen.

As for your comment about the MTNTK fix kit being the problem here.....There are inherent issues with this motor design, electronics, controls, and mapping strategy that require a lot more attention to the outside of the motor to make them live.

1) These motors are very temperamental to fuel injector issues and oil cap venting. I have been preaching about the lack of venting from the stock cap since the Dragon days and was told I was crazy here on the forum.

2) I've also been touting everyone on getting injectors ultrasonic cleaned and flow tested during rebuild's the last few years. Injector placement on this motor leads to carbon build which then messes up the fuel flow. BRP learned this a long time ago and scrapped the SDI. Since these motors run so lean with stock mapping (especially '13's) they cannot handle anything less then ideal conditions, fuel flow, quality fuel, perfect TPS settings, proper storage and use. I have been having injectors cleaned and flow tested in previous years however, I am beginning to see injector fault codes also prior to engine failure's which indicates an electrical problem with the injectors as well as the carbon build up issue. Ultrasonic cleaning and flow testing an injector with an electrical fault is useless.

Take a partially plugged fuel injector causing a fuel flow pattern issue in a transfer port, a less than ideal fuel filter micron media that allows for reduced volume but with good fuel pressure, and you have a recipe for disaster with a lean mapped motor.

Then take less than ideal TPS settings, lean mapping, oil vent issues, crank seals that seem to be failing at early intervals, a noisy electrical system (that's a whole other discussion), along with what I have described above and you'll see that the 600/800 CFI-2 is a very temperamental motor to keep from having an engine failure. I'm not saying it can't be done but the struggle of challenges is real and attention to the details outside the motor is a must.


Early this year I started replacing injectors on all top ends and motor rebuilds with mileage near 1,500 miles instead of ultrasonic cleaning and flow testing. $260 from Polaris for injectors is cheap compared to the heart ache of a comeback or a heli ride and a burndown.


Hmmm.
I agree with everything you are suggesting here.

One thing I did not emphasize was when I disassembled the engine, I noticed both pistions had a very fine "paste' covering the skirts. This past reminded me of oil mixed with aluminum powder. I'm wondering if the oil was getting starved to both cylinders causing the rings to micromachine off the cylinder coatings??? Someone else told me about an experince where a crank bearing siezed so was rotating in the case causign somthing simular.... Also, I checked my oil cap again and if I blow through it even at a level position and rattling around the internal "ball" the cap seems to have a tough time venting. Wondering if the cap was the root cause.......
 
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RMK900Tractor

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I have installed over 35 MTNTK Fix kits without one comeback, failure, or runnability issue. The fix kit was not the issue with RMK900Tractor's motor failure. 3 seasons, 1,500 miles and an issue at -34*F. Something else caused this problem. I'll bet fuel injectors, crank seals, or some other fuel starvation issue.

At this time, I currently have an industry leading Polaris motor shops engine in my garage. Story is it has less than 100 miles and both the cylinder skirts have cracked and a "piston" skirt broke off and went through the bottom of the case. Pieces have filled the rod bearing so it needs a crank also. Worse one I have ever seen.

As for your comment about the MTNTK fix kit being the problem here.....There are inherent issues with this motor design, electronics, controls, and mapping strategy that require a lot more attention to the outside of the motor to make them live.

1) These motors are very temperamental to fuel injector issues and oil cap venting. I have been preaching about the lack of venting from the stock cap since the Dragon days and was told I was crazy here on the forum.

2) I've also been touting everyone on getting injectors ultrasonic cleaned and flow tested during rebuild's the last few years. Injector placement on this motor leads to carbon build which then messes up the fuel flow. BRP learned this a long time ago and scrapped the SDI. Since these motors run so lean with stock mapping (especially '13's) they cannot handle anything less then ideal conditions, fuel flow, quality fuel, perfect TPS settings, proper storage and use. I have been having injectors cleaned and flow tested in previous years however, I am beginning to see injector fault codes also prior to engine failure's which indicates an electrical problem with the injectors as well as the carbon build up issue. Ultrasonic cleaning and flow testing an injector with an electrical fault is useless.

Take a partially plugged fuel injector causing a fuel flow pattern issue in a transfer port, a less than ideal fuel filter micron media that allows for reduced volume but with good fuel pressure, and you have a recipe for disaster with a lean mapped motor.

Then take less than ideal TPS settings, lean mapping, oil vent issues, crank seals that seem to be failing at early intervals, a noisy electrical system (that's a whole other discussion), along with what I have described above and you'll see that the 600/800 CFI-2 is a very temperamental motor to keep from having an engine failure. I'm not saying it can't be done but the struggle of challenges is real and attention to the details outside the motor is a must.


Early this year I started replacing injectors on all top ends and motor rebuilds with mileage near 1,500 miles instead of ultrasonic cleaning and flow testing. $260 from Polaris for injectors is cheap compared to the heart ache of a comeback or a heli ride and a burndown.


Hmmm.

I was also thinking about your TPS setting comment which got me thinking about the occasional DET issue I was having before the piston seizure. The MTNTK guys told me some engines respond well to the kit so could gain some HP. I theorized more HP with the same amount of fuel will cause an occasional lean condition = DET. Back to the TPS sensor, I had purchased a harness for measuring the TPS and used a high accuracy FLUKE meter to set the TPS exactly to the service manual specification. Wondering if I could have offset the TPS adjustment some amount to add extra fuel to the entire map???
 

XCaSSAULT

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I was also thinking about your TPS setting comment which got me thinking about the occasional DET issue I was having before the piston seizure. The MTNTK guys told me some engines respond well to the kit so could gain some HP. I theorized more HP with the same amount of fuel will cause an occasional lean condition = DET. Back to the TPS sensor, I had purchased a harness for measuring the TPS and used a high accuracy FLUKE meter to set the TPS exactly to the service manual specification. Wondering if I could have offset the TPS adjustment some amount to add extra fuel to the entire map???

Your better off getting a power commander fuel controller and doing it that way. Why chance it
 

RMK900Tractor

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Your better off getting a power commander fuel controller and doing it that way. Why chance it

Ya, I thought about that but I am sick of poking button then besides need an A/F gauge to understand what you are changing which then means need to modify the exhaust to install a sensor, etc.... Going back down the rabbit hole just like I did with the turbo system. I would rather just buy a stock AXYS - probably cheaper in the long run.
 

RMK900Tractor

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Pretty quiet here, what are you doing on this sled now?

Standstill right now, I was traveling for work all last week so not much has happened.

After a lot of discussions and thought I have decided to:
- Change crank seals
- Cylinder reworked
- Have someone check the crank indexing & bearings
- New set of injectors
- New MAP sensor
- New exhaust sensor (nobody mentioned this but I do know it is there to monitor the pipe temperature so if it gets too hot it richens the air/fuel mixture)
- Better venting in the oil reservoir
- MTNTK lightweight pistons
- Adjust the TPS sensor to richen up the air/fuel mixture (always had a detonation issue once the MTNTK kit was installed so must be making more power than stock so need a bit more fuel)
- Trying to stay away from adding a fuel controller and A/F gauge.

Probably cheaper to buy a new Axys!

Hopefully, this will resolve the issue.
 

Dazzler

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I have installed over 35 MTNTK Fix kits without one comeback, failure, or runnability issue. The fix kit was not the issue with RMK900Tractor's motor failure. 3 seasons, 1,500 miles and an issue at -34*F. Something else caused this problem. I'll bet fuel injectors, crank seals, or some other fuel starvation issue.

At this time, I currently have an industry leading Polaris motor shops engine in my garage. Story is it has less than 100 miles and both the cylinder skirts have cracked and a "piston" skirt broke off and went through the bottom of the case. Pieces have filled the rod bearing so it needs a crank also. Worse one I have ever seen.

As for your comment about the MTNTK fix kit being the problem here.....There are inherent issues with this motor design, electronics, controls, and mapping strategy that require a lot more attention to the outside of the motor to make them live.

1) These motors are very temperamental to fuel injector issues and oil cap venting. I have been preaching about the lack of venting from the stock cap since the Dragon days and was told I was crazy here on the forum.

2) I've also been touting everyone on getting injectors ultrasonic cleaned and flow tested during rebuild's the last few years. Injector placement on this motor leads to carbon build which then messes up the fuel flow. BRP learned this a long time ago and scrapped the SDI. Since these motors run so lean with stock mapping (especially '13's) they cannot handle anything less then ideal conditions, fuel flow, quality fuel, perfect TPS settings, proper storage and use. I have been having injectors cleaned and flow tested in previous years however, I am beginning to see injector fault codes also prior to engine failure's which indicates an electrical problem with the injectors as well as the carbon build up issue. Ultrasonic cleaning and flow testing an injector with an electrical fault is useless.

Take a partially plugged fuel injector causing a fuel flow pattern issue in a transfer port, a less than ideal fuel filter micron media that allows for reduced volume but with good fuel pressure, and you have a recipe for disaster with a lean mapped motor.

Then take less than ideal TPS settings, lean mapping, oil vent issues, crank seals that seem to be failing at early intervals, a noisy electrical system (that's a whole other discussion), along with what I have described above and you'll see that the 600/800 CFI-2 is a very temperamental motor to keep from having an engine failure. I'm not saying it can't be done but the struggle of challenges is real and attention to the details outside the motor is a must.


Early this year I started replacing injectors on all top ends and motor rebuilds with mileage near 1,500 miles instead of ultrasonic cleaning and flow testing. $260 from Polaris for injectors is cheap compared to the heart ache of a comeback or a heli ride and a burndown.


Hmmm.


Sorry Dave, I didn't see this reply.
As usual your posts are very informative and to the point..
I was just offering my opinion and that being, I have not had much luck with the Mtntk kit in the 2013 sleds, my engine rebuilding is just to help friends on the side.. I have only installed half a dozen fix kits, and I don't do this for a living or entertainment. My only point is, I think OEM pistons from 2013 up are much better that the previous years, and MTNTK kits are no longer a necessity in the later 800's and the fact that both 2013's didn't make 300 miles on the fix kit, so went back to OEM pistons and they're well over 700 miles now??
I totally agree with you on good fuels, regular filter change, and proper storage..
 
I have a thought about us guys that add 2 stroke oil to the fuel tank every time we fuel up,
Our computers-ECU , can compensate to allow for a few variables ? Now when we add oil to the gas at say 40/1 naturally that would be leaning out the air fuel mixture compared to 100% straight gas. I know the ecu compensates up to a percentage with temps fuel and timing variables but we must be tricking the computers fuel ideas by adding oil to the fuel their by leaning it out?
Running in cold temps
Low elevation
Marginal / borderline 91 oct fuel
He'll let's add a pipe and can:juggle::juggle::juggle:
How many percent can our computers adjust the fuel feed on these sleds?
 

XCaSSAULT

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I have a thought about us guys that add 2 stroke oil to the fuel tank every time we fuel up,
Our computers-ECU , can compensate to allow for a few variables ? Now when we add oil to the gas at say 40/1 naturally that would be leaning out the air fuel mixture compared to 100% straight gas. I know the ecu compensates up to a percentage with temps fuel and timing variables but we must be tricking the computers fuel ideas by adding oil to the fuel their by leaning it out?
Running in cold temps
Low elevation
Marginal / borderline 91 oct fuel
He'll let's add a pipe and can:juggle::juggle::juggle:
How many percent can our computers adjust the fuel feed on these sleds?

In my opinion the fuel injection systems on these and really all sleds is a very “archaic” system.

The best and most adaptable injection systems control fuel flow based on mass air flow input and a real oxygen sensor to achieve a near perfect air/fuel ratio.

The system our sleds have delivers fuel based only on air temp and pressure and exhaust temp, then based on throttle and crank position deliver the fuel. Only fail safes are knock sensor and temp sensor both of which attempt to adjust timing to avoid engine failure. But in a 2 stoke rocking 8,000rpm with .005 piston/cylinder clearance those fail safes are just slightly better then nothing. Think of the tps like a dimmer switch, more throttle=more fuel with the ecm making adjustments based on exhaust temp and ambient air temp. That’s it!

Not much better then a carburetor in a sense. At least it works at any angle the sled is in (unlike a carb)

To your point about adding oil making the mixture more lean. I think (and I may very well be wrong) the only way this could happen is the oil very marginally slowing the flow through the injectors. I doubt the little amount of oil would effect exhaust temps and I’m willing to bet that only a few ounces of oil will lean your sled by 1% plus or minus a .2%. The small amount of oil added to the fuel is more beneficial then losing that 1% because otherwise your spraying straight gas on your cylinders. Unlike the carb sleds of yesterday where the oil and gas mixed in the fuel pump.
 
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pacattack

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There should be sticky with a list of all the mods to do to a stock pro to make the most reliable as possible...

I got a 2014 as well with about 1500 miles on it. Everything on the sled is stock. I am compiling a list of mods to do this summer to avoid a blow up on the trail. So far I have got this:

-MTNTK Fix kit -or- RK Tek replacement piston kit (I honestly don't know how to choose between the two)
-Turn up the oil pump
-Get new injectors (or get current ones cleaned)
-Clean electrical contacts and apply dielectric grease
-Oil cap venting

What else am I missing.

Don't mean to hi jack the thread or anything but I feel like there's good information in here already that applies to sleds that have blown up and that have not blown up yet.
 

RMK900Tractor

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There should be sticky with a list of all the mods to do to a stock pro to make the most reliable as possible...

I got a 2014 as well with about 1500 miles on it. Everything on the sled is stock. I am compiling a list of mods to do this summer to avoid a blow up on the trail. So far I have got this:

-MTNTK Fix kit -or- RK Tek replacement piston kit (I honestly don't know how to choose between the two)
-Turn up the oil pump
-Get new injectors (or get current ones cleaned)
-Clean electrical contacts and apply dielectric grease
-Oil cap venting

What else am I missing.

Don't mean to hi jack the thread or anything but I feel like there's good information in here already that applies to sleds that have blown up and that have not blown up yet.

My list back a couple of post ago is my list of things I plan to do. However, I have changed my mind on the MTNTK pistons, going back to either Polaris stock or SPI. The reason for that is after talking with a local engine rebuilder and reading Indydan post in the below link.

I am sure I will get a lot of hate mail regarding the MTNTK comment but the forged pistons just seem to be a problem and only make 500 miles before trouble. And yes, lots of MTNTK kits have thousands of miles but I am taking the safe route. The perceived performance and minor HP gains are not worth the gamble to me anymore.


https://www.snowest.com/forum/showthread.php?t=433563
 

XCaSSAULT

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There should be sticky with a list of all the mods to do to a stock pro to make the most reliable as possible...

I got a 2014 as well with about 1500 miles on it. Everything on the sled is stock. I am compiling a list of mods to do this summer to avoid a blow up on the trail. So far I have got this:

-MTNTK Fix kit -or- RK Tek replacement piston kit (I honestly don't know how to choose between the two)
-Turn up the oil pump
-Get new injectors (or get current ones cleaned)
-Clean electrical contacts and apply dielectric grease
-Oil cap venting

What else am I missing.

Don't mean to hi jack the thread or anything but I feel like there's good information in here already that applies to sleds that have blown up and that have not blown up yet.


2014 with 1,500 miles I would do compression check and inspect pistons/cylinders through valve slots and plug holes. If all checks out I think all’s one should do is;
Oil cap
Oil pump
Primary balance
Clean both clutches good, check deflection/alignment
Clean valves
Trs coolant bypass

Ride it for another season and then.....
Have Indy specialty’s do there cylinder coating process
Replace pistons with spi’s or stock
Have injectors cleaned
Replace fuel filter
Clean valves
 
X assualt , do you personally run an Indy Dan cylinder or one of his motors?
I'd like to believe many of us on here could build an 800cfi that lasts equally as long and healthy of life as a Dan motor. I'm not bad mouthing him but building 800 cfi is a little short of rocket engenering. I do like his cylinder finish honing ideas but I'm not so sure about the forged Pistons are crap theory.
So far this has been a good informative thread for the do it your self kind of guy.
 

XCaSSAULT

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X assualt , do you personally run an Indy Dan cylinder or one of his motors?
I'd like to believe many of us on here could build an 800cfi that lasts equally as long and healthy of life as a Dan motor. I'm not bad mouthing him but building 800 cfi is a little short of rocket engenering. I do like his cylinder finish honing ideas but I'm not so sure about the forged Pistons are crap theory.
So far this has been a good informative thread for the do it your self kind of guy.

I do not run a Indy specialty’s motor. I bought into all the hype of the fix kits with forged pistons.

That was before I read his rant about forged pistons. That alone has not shifted my opinion on forged.

Back in my short track, wide open across a lake days taught me cast is a safer more reliable bet then forged. 2 stokes in general don’t play well with consistent throttle in any range. Varied throttle is obviously best.

Can forged work...yes of course. But if your gonna run forged your gonna have to be more aware of how u use your sled, like longer warm ups and waiting for temps to settle down after short stops, lots of varied throttle, etc. plus u better be on top of maintnece like fuel filter change every season, valve cleanings, and no gas older then a month.

Cast has a much better chance of surviving when things get out of the “perfect” zone of all those things. That’s prolly why polaris and all other manufacturers chose to run them.

I won’t belive anyone who says they can feel a noticeable difference in performance between cast and forged. (That be fun, line up 6 exact same sled, only one has forged, see if a expert can tell)

I’m not a forged basher. They have a place. I have them in my sled now. But if your talking reliability. Cast is the way to go.
 

pacattack

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Thanks for the info. Glad my offseason may have gotten cheaper... assuming pistons look good from the visual.

I mayyy do the injectors and fuel filter because I’ve just bought the sled and don’t know how it’s been summarized in the past.


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