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850 pitted & etched cylinder bores


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#1 ctdls

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Posted 21 May 2020 - 08:08 PM

When I first pulled this cylinder head I thought a little corrosion on the bores. I don't know if the photo quality will show the etching & pitting in these cylinder bores. You run your finger over it & you think there is no way the rings will seal...it is very rough. This is a mountain sled & probably in 3000 km area. I'm curious if this is common with bore finish & if anyone else has seen this.

 

No complaints from the owner how it runs. BRP oil & it uses it. I suspected power was down when I clutched it last season as it would not run how I normally set them. 

 

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#2 Jarret

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Posted 21 May 2020 - 08:18 PM

Looks like rust from moisture. Was it sank? Also is that a hole in the piston in picture 3?


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#3 mike0chek

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Posted 21 May 2020 - 09:07 PM

no compression check before tearing it down? sure does look like a hole in that pic!



#4 wwracer

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Posted 21 May 2020 - 09:49 PM

:bighair


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#5 Caper11

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Posted 21 May 2020 - 09:57 PM

Yes I have seen that before, engine only had 300miles approximately.
Is yours a 2017 engine?????


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Edited by Caper11, 21 May 2020 - 09:58 PM.

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#6 mike0chek

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Posted 21 May 2020 - 10:03 PM

Yes I have seen that before, engine only had 300miles approximately.
Is yours a 2017 engine?????


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was poor engine performance the reason the cylinders were pulled at 300 milies?



#7 Caper11

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Posted 21 May 2020 - 10:17 PM

was poor engine performance the reason the cylinders were pulled at 300 milies?

Blew up, cant remember if that engine was a crank failure or a piston failure.


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#8 Gin la pine

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Posted 22 May 2020 - 06:30 AM

its sprayed iron...its supposed to be more porous hence the roughness i guess and bein iron its prolly rusting if sitting for too long ....I would believe it hapens to all of them..during the summer....at least it happens with packaged cast iron cylinder (or sleeved) sitting for over a year on a shelf....unless they are really well oiled and turned upside down couple of times a months i guesss...



#9 ctdls

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Posted 22 May 2020 - 07:27 AM

Thank for the replies, in my original post  "No complaints from the owner how it runs. BRP oil & it uses it."

 

No reason for a compression test, this is not a tear down only a cylinder head removal. The reason for removing the head was to increase compression, re machining of the stock head. In hind sight I would have like to have completed a compression test as I'm curious if it would have shown a problem or not. 

 

The comment about the coating is my concern & the reason I've brought up. I suspect there are other motor's with issue & owners don't know. This is mountain sled & there is no evidence & very unlikely is has ever been submerged. The full synthetic BRP oil should provide very good corrosion protection in normal conditions even if there is a maintenance neglect.

 

I've seen many motors that will have what looks like to be corrosion on the bores especially after storage. The motors start & it's gone, surface only. This is not surface corrosion, it is etched & pitted.

 

Speaking with one small engine machine shop, they have seen this many times on Kawasaki ATV........using the same bore finish.

 

Yes it is a 2017 motor.



#10 A7M266D

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Posted 22 May 2020 - 07:40 AM

For the amount of oil an 850 uses and the amount laying in the exhaust ports if you pull the Y pipe off I can't believe they could ever rust.  Like you said though its on on the surface and nothing to worry about.  It will be gone as soon as it fires up.


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#11 ctdls

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Posted 22 May 2020 - 07:46 AM

This is "not" on the surface.



#12 Ski-B

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Posted 22 May 2020 - 08:25 AM

I have had three 850 top ends apart and everyone on them looked like this. Deep rust pits in the cylinder bore. Even after a ball hone it is still there.

 

All using BRP oil and cylinders were removed for performance modifications. Motors were running well before removal.


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2018 XRS 850 Sons sled.

2017 Freeride 860R etec. 860BB. Daughters sled.

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2015 BCX  800R etec. Trail ported. Spare sled.

2014 BCX 800R etec. All stock. Spare sled.

 


#13 ctdls

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Posted 22 May 2020 - 08:38 AM

I'm told this material is soft enough my rigid hone would clean it up, I've not tried that as I'm sure the piston to cylinder would go beyond where it should be. The other issue I have is the problem would still be there & re occur.

 

The three you had apart did you correct the problem?



#14 Ski-B

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Posted 22 May 2020 - 08:54 AM

I was concerned about the look of the cylinder bore finish but the engine builders were not. Two were ported and the other one was a big bore exchange kit. The ported cylinders were cleaned up by the company that ported them but the deep pits were still visible. 


2020 Freeride 850. My ride.

2018 XRS 850 Sons sled.

2017 Freeride 860R etec. 860BB. Daughters sled.

2015 Freeride 800R etec. All Stock. Wifes sled.

2015 BCX  800R etec. Trail ported. Spare sled.

2014 BCX 800R etec. All stock. Spare sled.

 


#15 ctdls

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Posted 22 May 2020 - 09:46 AM

Tx's for that Ski-B, I'm inclined to go along with your engine builder comments. Probably the reason I cut the head & have re assembled everything.

 

I'm guessing that you had expected results form the engines that were reassembled with the visual cylinders of concern.

 

Also curious if anyone has brought this to the attention of BRP service & has had any feedback from them.






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