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Discussion Starter #1
Hey everyone this is my first time posting on this forum. I have had a few sportsman atv's including a 850 xp which I sold this spring when I bought my RZR xp 900. Anyway my dad also has a 850 xp that he rolled a couple years ago and the throttle was pinned for a very short time while it was upside down. I replaced all the broken parts on the machine and it has ran fine until a few months ago when the engine literally exploded. We are thinking that it blew up from when it ran upside down. It punched a couple of holes in the block and when I look inside with a flashlight all I can see is complete carnage. Connecting rod pieces and piston chunks everywhere. From what I can see from the holes the cylinders have deep gouges in them. This engine is pretty much just a boat anchor now and my dad just wants to put a new crate engine in. The problem is Polaris has stopped making crate engines for 2010 850's but they do make them for the 2013's. Are the engines the same? Will it bolt right up? Any info would be great! Thanks a lot for any replies.


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Also what does a Polaris short block replacement engine include? From the picture it looks like it is a complete engine minus all fuel and electrical components. When I think short block that means no head but I am hoping that this would come with it.


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Welcome to the board. :med:
 

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Well the short block shows -2012-2014, but the case assembly, which would be the mounts, show 09-13. Not sure what the difference in the short block assembly is. Motor mounts are the same on 2011-2014.
 

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I am no expert, but from my understanding the 2010 is just an 850, and starting in 2012, they are an 850 HO. So you might need more than just an engine if you swap in the 2013....but might be worth it (10% more power).

Sean
 

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I doubt it was from running upside down. There have been quite a number of 2011 850's that grenaded out the side.

They changed up the throttle body and such in 2012, so I am not sure what all you would need.
 

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When my 850 suffered a complete failure at less than 1000 miles the replacement with labor was right at $6500. The valve covers, water pump, starter and charging system were used from the old engine. I know what it cost because I got a copy of the bill.
 

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DSC_0079_zps82fe2537.jpg

317380_227344243981736_1700006389_n.jpg

BOOM!!!! rod goes through the block :p
 

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Discussion Starter #9
Thanks for all the input guys and wow that engine really exploded! The reason I was thinking it popped from the upside down rpm redline because I was looking at one of the connecting rod pieces on the crank end and it is scored bad from what looks like lack of oil. It is just a guess at this point and really doesn't matter I suppose. From what I understand of the H.O. Engine the throttle body's were larger for one thing. I don't know about any other differences although there could be some. I might have tracked down a new 2010 engine anyway. I will find out this week.


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I would wager that you would need the HO fuel system components as well as an ECU for an HO.
 

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^^ This is what I was thinking.
 

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The engine internals are identical from 2009 thru 2014. You will be fine to purchase a 2013 short block however a 2013 long block will not work. What changed in 2012 and newer when they came out with the HO model was the throttle body, airbox and (cylinder head intake tract shape). << The 2013 cylinder head will not bolt up to your 2009 throttle body. Just to clarify once more - all internals are the same from 2009 except for the intake tract is a different design.
 

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So cam, timing, everything else is the same? Doesn't sound exactly correct.
 

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I thank the pistons on the H/O where 12.5 to 1 and the pistons on 09-11 are 11.5 to 1 or did they just mill the head down I thank the cam profile changed
 

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09 10 have the same cam 11 14 have the same cam 09 12 have the same piston 13 14 have the same piston 12 14 have the same heads
 

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09 10 have the same cam 11 14 have the same cam 09 12 have the same piston 13 14 have the same piston 12 14 have the same heads
Pistons & compresson never changed in the HO - part numbers yes just because of different runs & tolerances.

The only difference between the standard and HO is:

Intake, Throttle Body and EFI - fuel & timing settings. The biggest gain was the airbox airflow as the 2009-2011 intake was really restrictive.

Keep in mind the new Scrambler 1000 uses the same cam and throttle bodies as our 850's! The 1000 just has larger bore, stroke, valves and ports..
 

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So what compression ratio is a 2013 850 ho the owners manual shows 12.5 to 1 and the owners manual for my 09 shows 11.5 to 1
 

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So what compression ratio is a 2013 850 ho the owners manual shows 12.5 to 1 and the owners manual for my 09 shows 11.5 to 1
I'll have to go out in garage to get a picture of the stock 11:1 piston which are dished about 2 mm however here is a picture of the 12.5:1 pistons I'm running now.
 

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Do you know if they changed the CC of the combustion chamber
 
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