Plating on cylinder walls coming off? (pics)

[e46m3]

Plating on cylinder walls coming off? (more pics)

I just bought this sled recently and removed the cylinders to inspect a scored piston. After inspecting the cylinder walls, it looks like the plating on the cylinder is coming off. Both the pistons have deep scratches on them that line up with the marks on the cylinder walls. Has anyone else seen this?

mag side piston

pto side piston

mag side cylinder

pto side cylinder

 

[skibreeze]

Yep, plating is coming off, looks like a fairly fresh rebuild. Gonna need to find out why it went down again.

 

[e46m3]

The guy I bought it from said it only had about 500 miles on the rebuild. It had nitrous on it but he said he never sprayed the new engine as it was not tuned yet. What would cause the plating to come off?

 

[Z-Man]

Looking at where it is coming off and the hone marks in that cylinder I would say that who ever put the engine together over honed it and possibly wasn't using the right type of hone.

It also looks like it got hot in that area possibly due to clearance on the pistons being to tight or improper break in. What type of pistons were installed in this engine? Factory or after market? Did you mix oil with the first tank of fuel for added lubrication of the new pistons during break in?

 

[e46m3]

I bought the sled after the engine had 500 miles on the rebuild so i don't know. The pistons are new '06 Polaris pistons. I talked to Millenium Technologies and they said these cylinders shouldn't be honed and if they are its only to do light clean-up. Thanks for the info.

 

[Z-Man]

I bought the sled after the engine had 500 miles on the rebuild so i don't know. The pistons are new '06 Polaris pistons. I talked to Millenium Technologies and they said these cylinders shouldn't be honed and if they are its only to do light clean-up. Thanks for the info.

Yes, light clean up with a diamond hone usually in a 45 degree crosshatch pattern to help seat the new rings. It looks like they put some serious gouges in there when they honed it.

 

[e46m3]

As far as fixing it. I was thinking of replating cylinders and replacing pistons. Should I be worried about any greater issues causing this?

 

[sw]

Excellent footwork so far! Great pictures by the way, and this looks like you've caught a problem before it got exponentially worse. In my book this is the biggest problem with 900's is their suseptebility to overheat. Millenium is reputable company to deal with. The '05 manual gives excellent info on determining if cyl's are in tolerance for dimensions. So document/write down what you have, compare against new pistons and go from there. Also if you or your friends have any dirt bike reference material, by a man named Eric Gorr in particular, I've found his two stroke info quite helpful and interesting. Good luck.

 

[slash]

I just bought this sled recently and removed the cylinders to inspect a scored piston. After inspecting the cylinder walls, it looks like the plating on the cylinder is coming off. Both the pistons have deep scratches on them that line up with the marks on the cylinder walls. Has anyone else seen this?

mag side piston

pto side piston

mag side cylinder

pto side cylinder

What does the inside of the dome look like ,the cyl looks like it got real hot at the exh bridge. Kind of like he put in new pistons and just rode it instead of seasoning the the top end..

 

[e46m3]

Seasoning the top end? I will post pics of the head tonight. The domes look ok.

 

[Mech Engr]

900 cyls

You can find re-manufactured (and replated with nikisil) cylinders on evilbay for around $200 each. Don't know what type of quality they are but there are 3 or 4 vendors that rework/replate them.

Big John

 

[e46m3]

The guy i bought the sled from said he never sprayed the new engine. But the nitrous was armed in the controller when i bought it (noticed after i got home). The system was suppose to have been tuned for the 25hp shot. This was before the motor was rebuilt. He put the 45hp nozzles in after the engine was done, but never had it tuned. I'm begining to think he might have sprayed it and that is what caused this.

 

[diamonddave]

The guy i bought the sled from said he never sprayed the new engine. But the nitrous was armed in the controller when i bought it (noticed after i got home). The system was suppose to have been tuned for the 25hp shot. This was before the motor was rebuilt. He put the 45hp nozzles in after the engine was done, but never had it tuned. I'm begining to think he might have sprayed it and that is what caused this.

I'm in agreement 100%

Probably never had it tuned because he couldn't get it tuned.

 

[machineman]

I agree probably the hit not tuned. Nitrous transfers a incedible amount of heat into into the ring lands. Exhaust bridges are hot spots and under intense heat can swell and scrub the pistons and swage the ring lands pinching the rings and killing the compression. This can come from the nitrous, insufficient warm up and the high demands on the engine. I would renik and new slugs. I have in the past cleaned up pistions and freed the rings that look like this. Also polished the bad spots on the bridges a couple of thou as to make a low spot in the cyl wall for the rings to bridge over as they pass by. I don't recomend this but have done it before.

 

[alsled]

I bought the sled after the engine had 500 miles on the rebuild so i don't know. The pistons are new '06 Polaris pistons. I talked to Millenium Technologies and they said these cylinders shouldn't be honed and if they are its only to do light clean-up. Thanks for the info.

Were the jugs replated by millenium for the rebuild 500 miles ago?

 

[e46m3]

I dont think they were replated at all. They look like they were just honed. The normal cylinder wear on the cylinder wall can be seen. It lookes like the cylinders that had 2700 miles on them were just honed and reinstalled.

 

[e46m3]

Pics of the cylinder head

Here are some pics of the cylinder head. I think it looks alright to me. What do you guys think?

 

[BIGGDAWG]

the head looks fine