PTO Cylinder/Piston Scarring - 2015 RMK Pro 600

[ac14]

I got a DET code about 10 miles into a ride the other weekend, had to limp it back home for the day to check it out. I started pulling it apart and noticed the PTO side spark plug had an odd grayish looking substance on it so I figured it maybe it wasn't getting enough fuel. Mag side spark plug looked completely normal so I thought it was most likely the injector on the PTO side. Pulled off the fuel rail and injectors, cleaned them (PTO side had looked a little dirty, then again so did the mag side), and then put it back together. When I started it up it seemed to only be running on one cylinder so so I checked compression on both cylinders with mag side being about 130 and PTO side was 90. So I started to dig deeper..

When I got the head off I noticed some "not insignificant" scarring on the PTO side cylinder and piston. Found some metal shavings on that side as well.. Previously when I've seen this it's been a cracked/broken ring, but they both seemed to be fully intact on the piston still. I did notice that the piston (both the mag and PTO side) had a little bit of side to side movement in the cylinder which shouldn't be there.

The sled is bone stock, just bought it this year with 300 miles on it. Put about 500 more of my own miles on it, never let it go above 140F and then this happened.

I have a couple questions here (first time working on a Polaris so bear with me):

1. What could have caused this scarring and metal shavings in the cylinder? Is the piston on some sort of bearing at the end of the crank shaft? Maybe that's shot and a piece of metal came off of that? Blocked oil injector? Not getting enough fuel? I'm going to fix this and don't want this happening again after a couple rides..

2. What's the best course of action for a fix? I'm no machinist, but i'm not sure the scarred cylinder could be rebored to stock (maybe i'm wrong). I have looked into a couple different 660 big bore kits and I have been wanting to get the Carl's Cycle setup, I just haven't been able convince myself it's worth the money - now I HAVE to dump some money into the sled so might as well get what I want, right?

The thing ran like a DREAM all season with no issues, I was just getting ready to sell it to upgrade to an Axys 800 ? (at least I didn't sell it to someone and have it blow up a week later, good karma coming my way? hopefully?)

 

[turbolover]

You can have the cylinder replated and put it back to stock form for much cheaper that a big bore kit.

The nickasil coating has apparently been damaged. It can be repaired and reapplied like chrome then you put new pistons and rings in it and should be good to go.
Replace all the seals and gaskets and you'll be back in business.

Sent from my Pixel 5 using Tapatalk

 

[ac14]

You can have the cylinder replated and put it back to stock form for much cheaper that a big bore kit.

The nickasil coating has apparently been damaged. It can be repaired and reapplied like chrome then you put new pistons and rings in it and should be good to go.
Replace all the seals and gaskets and you'll be back in business.

Sent from my Pixel 5 using Tapatalk

Thanks for replying. I was looking at a couple different top end kits online and they looked pretty affordable. Where would you normally get the cylinder replated? I have a couple of buddies that are machinists but I'm not sure where to find bore size/tolerances information or the plating information.

Any idea what typically causes this? Just don't want to drop money into it just for it to happen again.

 

[BeartoothBaron]

I've never used them, but heard Millennium Tech (https://www.millennium-tech.net/) thrown out as a good place to get jugs repaired. It's not something a typical machine shop can handle. The most they could do is hone the cylinder, but unless they do a lot of two-stroke work, that's also something better to send in to a specialist. I love the idea of the 660, based on reports, but have never rode one myself and ended up getting a good deal on an 800 last summer. If you really want one, now would be the time to do it: re-plating is required after the cylinder is bored for the bigger piston. Still, you're talking about spending double for a big bore vs. a fixing it stock.

As to what caused it, there are several possible causes that come to mind. Bad injector causing a lean out, not enough oil (I know turning up the oil pump is standard procedure on the Pro 800s, probably a good idea on the 600 too), overheating (could have happened before you got it and took a while for the damage to snowball), bad gas, or running low grade or eth gas in non-eth mode. Some pictures would help, but I'd definitely get the injectors cleaned and turn up the oil pump before you put it back together.

What direction you go depends on your budget. 600s have pretty good resale, and a new engine should be a bonus. A 660 isn't worth doing unless you plan to keep the sled for a few years; it'll add some to the selling price, but not what it cost. Since you mentioned the AXYS, there's a good chance you'd enjoy that more than a Pro 660 (you may find the motor more fun than the 800HO, but not enough to overcome the older chassis). If you're already thinking of going that way, just have the cylinder re-done properly, use OE pistons, and trade up when the time is right.

 

[retiredpop]

It could also be caused by a leaking crank seal on the PTO side although at 800 miles that's probably not likely.

 

[BeartoothBaron]

^ That's a good thought, and the low miles probably make it more likely. With only 300 miles when purchased, it could be the sled was rode one season and then sat without being used for years. Could be the seal was starting to go when you got it. That kind of thing can also contribute to fuel and/or injector issues. Seals like that should last much longer (my old 600 is going on 20 with the original seal), but some of these things aren't made as well as they once were...