Did the chain jump a tooth or did the timing gear itself move? Is there a keyway or just press-fit? On a side note, my son's hockey team just played a tournament against a team from Kitchener and a few others around Toronto.

 

I won't know for 100% until we get the motor out.
It appears the gear slipped. They are pressed on. I plan to weld it. The upper one has a shear pin so that should fail in the future

 

Hmmm, I would've assumed both were key'd. I would think a small tack weld would do the job.

 

IMG_20140203_110339 by rangerbob316, on Flickr


image by rangerbob316, on Flickr

The valves were touching the piston as you can see in the one picture

 

What's the easiest way to check the timing? I have all my plastics off now playing with tps. Would like to check this before I put it all back together if possible.

Sent from my SCH-I545 using Tapatalk

 

I can't answer for you, my dealer hooked it up to his computer and it told him.
After he pulled the cover off the top, you can use a flashlight and look down in to the motor and you can see the two tabs that SHOULD be lined up.

 

Wow that timing gear slipped a good amount. I think tack weld would be a good idea to prevent future failure.

Sent from my SCH-R970 using Tapatalk

 

My cam gear turned with 70 miles on the quad. Ruined the entire motor. Polaris told me they were going to rebuild the motor, I fought them, and got a brand new motor installed. I'm not happy with the quality of these machines!

 

is this a common problem?

 

Any updates Rangerbob316?

Sent from my SCH-R970 using Tapatalk

 

70hp is more than my first diesel Rabbit had and that was a 4 cylinder car.
The timing gear and flywheel should be keyed to the crank or the crank should have 2 flats machined with a match mark to orient them. The match-marked flywheel and gear should have a mating double D hole. The mechanical engineering intern that did this one need his head examined.

 

I agree crank gear should have a keyway.

Sent from my SCH-R970 using Tapatalk

 

just an update....
the piston smashed the exhaust valves. new ones on order, but there is a two week back order on them.
I'm still in shock that this happened and still wonder why the darn thing failed. Dealer is still saying water got in to cylinder. I'm not ruling it out, but I'm having a hard time figuring out how the water got in there...
Gotta look for a leak in my snorkel setup

 

If it ingested water you'd find a bent connecting rod and maybe damaged pistons not a slipped timing chain gear with bent valves.

From orbit via Android.

 

Repair-Invoice by rangerbob316, on Flickr

 

was it covered under warranty? because as said if it ingested water it would have bent one or both connecting rods. water doesn't like being compressed.

 

dealer just gave me the goods news.... Polaris is covering the cost of the repair!!
I called in to Polaris a few days ago to argue my case, citing that fact the Scrambler 500's have a keyed CAM gear, why doesn't a big bore like the 850???
My dealer hit up Polaris with the same argument on his end, and four hours later....
Free repair for me

Parts are still on a two week back order, but now i can sleep at night.

 

Good for you. And good for Polaris. They did the right thing.

 

Thats great news Bob...they did you right....I would like to see the melted plastic victims done right now....enjoy the machine when you get it back....its been away for a while...again congrats

 

Thats cool bob. hopefully polaris will do the same with my broken frame. im assuming your 6 month warranty is over with?

 

My 2013 scrambler also has this same problem the dealer is rebuilding the motor with an aftermarket crank where the gear is casted on the crank. And polaris is warranting the whole thing. Only 150 miles on mine thank god I bought the extended warranty

 

Anybody know if this has happened to any 850 Sportsmans ?

 

I was thinking the same thing. Is this a Scrambler only problem? Does the Sportsman have the same gear/cam setup? I've never heard of this problem before.

 

Exact same motors far as I know.

Sent from my SCH-R970 using Tapatalk

 

http://www.polarisatvforums.com/forums/polaris-xp/38347-2012-850-xp-engine-problems.html

 

It happened to my sportsman last summer

 

So Polaris is going with water ingestion as the cause?
I just don't see it...

From orbit via Android.

 

Thanks Swamp. At least there doesn't appear to be many.

 

UPDATE: hot off the press. Polaris has sent a BRAND NEW REDESIGNED crank to my dealer. It arrives Tuesday. Hmmmm, wonder if it will be keyed? Have to wait and find out. Photos on their way as soon as I get them.

 

Bob,

Did you ever find out what the difference was?

Mines going in tomorrow.....


Sent from my iPhone using Tapatalk