What would cause this engine damage???

[Snowmow]

I should understand this....but nope, please explain.

I hate not figuring this out lol.

this would mean that's where the crank pieces were pressed together at the factory have moved from their intended positions. Causing the Pistons to be out of time.

This is why people (usually in high performance applications) "weld" a crank, to keep it from ever moving at the pressed together junctions of the crank.

 

[LoudHandle]

On a two cylinder the crank is phased so the rod journals are exactly 180 degrees apart. If the crank gets out of phase (anything other than the intended 180 degrees on this engine) the fueling and timing is regulated by the pickups on the flywheel (mag end). So it makes sense that the mag cylinder would continue to run fine. The detonation or in this case pre-ingnition (because the piston is not where the electronics think it should be) is starting combustion too soon because the piston is still too far down in it's stroke. Essentially trying to run the engine backwards with the PTO cylinder and forwards with the Mag cylinder. That is the only feasible explanation for the radical crank damage. It takes a lot of force to fatigue steel to the point of cracking like shown in the pics.

 

[BC_mtn_rider]

Another possibility is the crank out of phase. Would make sense the mag side survived and the PTO did not. Do any clutch work lately? Blow any belts? Etc.

No clutch work was done...just cleaned at beginning of season. As far as belts, yes I did blow the Quickdrive belt the day before when the track cased a ditch. Also noticed the Jackshaft had a bit of play in it when I changed out the belt which is now an old warranty issue the dealer said was
The drive belt was on the Frits when the motor went. Was still in tact but started to seperate & was losing fibres.

 

[LoudHandle]

No clutch work was done...just cleaned at beginning of season. As far as belts, yes I did blow the Quickdrive belt the day before when the track cased a ditch. Also noticed the Jackshaft had a bit of play in it when I changed out the belt which is now an old warranty issue the dealer said was
The drive belt was on the Frits when the motor went. Was still in tact but started to seperate & was losing fibres.

May guess casing the ditch caused it go out of phase in the moment or two before the QD belt gave out. It really is impressive the torque and power these sleds have especially under full power and coming to a dead stop or near dead stop instantly.


Good luck with whichever direction you chose to go from here!

 

[RedRider]

Air leak on that side, cracked intake boot or leaking crank seal.

 

[sledhead9825]

Really hey? What fuel should I be running because every sledder in my region has been using this chevron 94 for years with no issues. I'm all ears on why I should switch fuels stations or grade. My partners E-tech has 5500 miles & its all he puts in his sled??? This DET has nothing to do with the fuel. The mag side piston was in perfect condition.
As far as how the sled sounded...it ran as strong as it ever has & sounded like it always has since new. The day before was in 3ft of fluff all day & was awesome. The 2nd day we were still in the pow in the morning then it blew on our way back.

I live in your area and have ridden 2 stroke sleds and bikes for years. I never run Chevron 94 only Shell 91. There are techs who feel the Chevron 94 is not the best 2 stroke fuel. Not saying Chevron 94 blew up your engine.

 

[BC_mtn_rider]

I live in your area and have ridden 2 stroke sleds and bikes for years. I never run Chevron 94 only Shell 91. There are techs who feel the Chevron 94 is not the best 2 stroke fuel. Not saying Chevron 94 blew up your engine.

Who knows...either way I'll change back to the shell 91. I used that in my Dragon before she blew up on me to!

 

[Trashy]

Probably not the cause here, but using an air impact gun to remove the clutch is rumored to lead to crank phasing issues which can result in the damage shown.

 

[BC_mtn_rider]

Yes, I have heard that as well. I personally have not used one but the shop may have....I hope not! Once everything is all back together, the Polaris dealership in my area will have to perform a series of tests to figure things out. I'm hoping to wash my hands of this sled as my bill is not even feasible at this point. They give a 30 day warranty but what good is that when my season is over. They only have 1 demo that seems to be always lent out to other guys with blown up engines as well!!! Like I said in some previous posts, it's my 3rd Polaris engine gone in as many sleds & 2 from the same dealer. I just hope they are reasonable & I cut my losses.
This one has been a tough pill to swallow for sure.

 

[Reg2view]

What are your thoughts on the deto sensor not working?

 

[diamonddave]

What are your thoughts on the deto sensor not working?

It might (could) have been working and just wasn't enough protection in this case, especially if only 1 cylinder is detonating and the other is fine.


Or maybe the deto sensor and signal interpretation to the ECU isn't sensitive enough when only 1 cylinder (appears) to have been detonating?


Just another reason why I think Loudhandle's theory of the crank going out of phase (time) is so logical. You could prove it mocking up the motor but warranty isn't going to cover the time at this point.

That crank damage is impressive to say the least. I would be curious if IndyDan has seen anything like that before.

But I still wouldn't use BC's Chevron 94.

 

[BC_mtn_rider]

I just wanna thank all u guys for your replies & opinions on this topic! I feel it helps me through this difficult time of tragedy! Losing a loved one is very hard!!! I'm always interested I what you guys have to say so keep em coming.
And yes...Indy Dan, if u would like to chime in, we'd love to get your take.
I just really hope this doesn't happen to anyone.
It'll be 10-12 days before the reassemble begins as I'm waiting for cyl re-plating, crank & Fixkit.

 

[JMCX]

Paying the dealer to fix that has got to hurt in the wallet. You will be lucky to get $7k for the sled even with a new motor.

 

[eddy]

Crank Picture

Notice the crack in the journal shows signs of displacement. This fatigue crack is likely the result of a lot of force over a longer period of time. While a momentary shock could do that kind of work, it would seem the piston erosion appearing at the same time as the crack is telling. The crack likely grew in the same period as the piston erosion was happening. This is consistent with explaining the failure of two components (crank and piston) simultaneously, due to the same root cause - detonation.

Can I prove it? We can only look at the evidence and make conclusions that agree with the physical properties. However, most of the time the bearings go out before the crank breaks under a detonation situation.

One thing I know is the crank is the single most expensive device in the whole machine and relatively hard to break. The MFR tries to save money and engineer the thing to be cheap and reliable - opposite forces indeed!

 

[BC_mtn_rider]

Dealer repair

Paying the dealer to fix that has got to hurt in the wallet. You will be lucky to get $7k for the sled even with a new motor.

Yes without a doubt it will be a huge bill from the dealer & that's why I'm hoping to wash my hands with that sled. I know the boys that run the shop, even ride with them & im hoping they'll help me out as they have the means to repair this for much cheaper then I can. I'm hoping they will give me a fair price for it as is & then they can fix it & resell it with a warranty & make some $. If their not interested then I am pulling the sled & will mess with it over the off season.
I was hoping for a fast repair so I could get back on the hills as we're seeing huge dumps right now up in Whistler but the whole crank issue has slowed things down so hopefully this all works out. I guess we'll see what happens!

 

[kiliki]

sell it as a roller and take the money and put it down on a new(er) one.

 

[eddy]

Engine

How about buying a used engine? No shame having a used engine in a used sled. Two hours labor - done.

 

[The Bob]

How about buying a used engine? No shame having a used engine in a used sled. Two hours labor - done.

The guys at Barrett Jackson wouldn't like that. Matching numbers!

 

[Uncle Bob]

We stopped using 94 octane in BC and went to 91 octane because it was reported to be highly oxygenated and the 91 was not.

After situations like this...

after problem after problem we also realized shell 91 is 10 times the fuel chevron 94 is

 

[BC_mtn_rider]

Moved on!

Yes, I'll be keeping my piston as reminder of why I should never buy a Polaris product again.
Starts to get old when it's the 3rd time. Pretty sure the E-tech won't let me down.

Well I did it boys...after 3 downed Poo sleds I finally made the switch & bought myself a 15 T3 163 with 300 miles & warranty until nov 2019. All I can say is WOW...10x the sled.