Help! What are my pistons telling me?

[Troutfrea]

Greetings,

I could really use some help determining if I need more than a new top end. I just pulled my heads off of my sled because I had very little compression and was preparing to replace the top end.

Can someone please let me know your thoughts on the sides of these pistons? Did a ring wear out? Not enough oil? Too much heat? Do I have a larger problem? To me it seems it would be a lack of oil/heat issue, but I don’t have a ton of experience and am only speculating. The mag side is the biggest concern but the PTO side shows a bit of the same problem. Let me know if better pics would help… it’s midnight and I don’t have the best light.

If it was your sled, what would you do? Should I do more than just a top end?

Other relevant facts:

2012 RMK Pro 600 w/ 155 track. Mileage is about 2500.

I just bought the sled a few months ago so don’t know the history of it. The guy I bought it from said he took good care of it. I had no reason to doubt him. Maybe I’m a sucker…

I initially thought I had an exhaust valve issue. Have them a good cleaning but it didn’t fix the issue at all. I then did the compression test and found out I had bigger problems.

This all started because I kept fouling the mag side plug.

PS - The pic showing both pistons shows the PTO side in the foreground.

Thank you for any help you provide!!

 

[Troutfrea]

Here are some better photos.

 

[davesilb]

Looks like over heating problem. This could be from lack of oil, lack of water cooling, or a cold slug of water hitting a hot engine from a short stop and a quick take off from that stop. Probably would need a bad thermostate to allow this slug of water thing to happen. If the barrels are not damaged a top end rebuild would be all I would worry about if you can determine what caused the overheating. I have had this 600 engine and it is really one of the best engines polaris ever built and had over a 10 year run with one of the fewest problems

 

[MATTELL]

Turn up the oil pump.

 

[Troutfrea]

Thank you both for your input. I will continue to evaluate and report back on the outcome

 

[czimpel]

Looks like they possibly ran it out of oil at low rpm locked up, but were able to get freed back up after cooling. Filled back with oil, got it running and sold it. I've seen similar damage not exact, but close to this. Or an extremely cold start full throttle bash.

Cylinders can be saved if it's just aluminum transfer. I used to use acid to clean the aluminum but found that making a paste of lye works much better. Clean them up, have someone knowledgable take a look at them if you are unsure before putting a new top end in it.

Grease the skirts of the pistons with low temp grease when reassembling with new parts. I'm also a firm believer in Polaris only brand gaskets as I've had too many poor gaskets from other off brand companies.

Good luck.

 

[Troutfrea]

Update - motor is out, heads and piston kit has been ordered from Millennium Technologies. I’m going to clean everything up as best I can and am looking forward to receiving the new product and putting everything together.

For some reason both thermostat bolts broke when I was taking everything apart. I have no idea why they would be in so tight. So far I’ve been able to get them out. What does everyone think; is using heat my best option!for extraction?

 

[fc8464]

Put a nut over the broken stud and weld them together. It will come right out.

 

[BeartoothBaron]

It's thread galling. It happens when dissimilar metals react and bind together; it's pretty common with aluminum. When it happens, the threads may be a little sticky, or it can be so bad that it's basically frozen, or it tears up the threads as you back it out. I like the idea of putting a nut over it and welding it; that'll put some heat in the bolt to help free it, although you'd have to move quickly. Also, I've found a lot more success if, instead of trying to back a stuck bolt straight out, I work the threads back and forth, doing 1/4 to 1/2 turn several times (the quicker the better), then 1/2 turn out or until it binds again, and keep repeating the cycle. I don't know if it's the heat it generates in the threads, or if it deposits some of the aluminum stuck to the threads back, but it's worked often enough that it's no coincidence.

If you don't have a welder, I'd lean towards taking it to a machine shop. A vice grip and some heat might get it to move, but there's a good chance it just makes a mess of it. I had a bolt broken off below the flange in the exhaust manifold of a project car I'm working on, and I took it to a machine shop. I tried an extractor tool, that just broke; thankfully I was able to get the piece out, because one of those stuck in place is borderline impossible to drill. It cost me $125, but considering how badly it was stuck and how expensive and hard to find a replacement manifold would be (it's on a Porsche 924 turbo), that was relatively cheap. This would be a lot easier to tackle: probably a half hour's work and $50 out the door. Oh, and after having to replace a water pump on my truck because I went to change the thermostat and all three bolts snapped right off, I keep a tube of anti-seize around and use that liberally on threads into aluminum. I (we) wish they'd do that from the factory... It won't help you much right now, but will save somebody this experience down the road!

 

[Troutfrea]

Thank you both for your replies. I will see if I can get some help with a buddy that welds. That combined with some heat and patience hopefully does the trick. Otherwise I will see how much a machine shop will charge me. I appreciate the help!

 

[Troutfrea]

Well, I wasn’t going to crack the crankcase open but realized the MAG side seal was leaking and likely the root of my entire problem. So it’s now cracked open. My plan is to clean everything really well to reuse the crank as while replacing both seals.

Is there anything I should look for when inspecting the crank? Make sure everything spins freely, there is no excessive play, etc.? Am I crazy to not do more than this if everything looks good?

Parts for the top end are on there way and my hope is to rebuild this weekend.

 

[BeartoothBaron]

Ideally, you'd check the crank runout and each of the bearings by feel. I've heard of people replacing certain bearings on the end of the crank (usually PTO) as a matter of course, but only on motors known to be hard on them. To check the bearings, you'd want to spin them by hand, feel for any roughness, and see if any have excess play by rocking them. You'll feel some movement, so don't panic as long as you don't have any that feel looser than the rest.

 

[Troutfrea]

Ideally, you'd check the crank runout and each of the bearings by feel. I've heard of people replacing certain bearings on the end of the crank (usually PTO) as a matter of course, but only on motors known to be hard on them. To check the bearings, you'd want to spin them by hand, feel for any roughness, and see if any have excess play by rocking them. You'll feel some movement, so don't panic as long as you don't have any that feel looser than the rest.

Great advice! I didn’t notice any issues upon initial inspection but will take a more detailed look this being using this great advice you provided.

Also, I noticed on another thread that you may have an applicable service manual. If so would you be willing to share it with me? Thanks so much! I will PM you my email.

 

[Troutfrea]

Does anyone have thoughts on which oil to run during break-in? I'm sure this sparks a heated debate as I noticed other posts with people on both sides of the fence. I was going to run full synthetic VES but the instructions that came with my pistons state to run a conventional oil. The Polaris service manual says to run a blended synthetic, so I guess that is a happy medium. My plan is to pick up a gallon of Polaris blue and use that up (including in my tank initially) and then transition to VES. Any red flags with this approach?

 

[BeartoothBaron]

I'm not sure what's best, but I'd minimize the amount of Polaris blue you run. It's a lot thicker and will have a harder time reaching the rod bearings in particular. Ideally, you'd want to pre-mix some (I've heard 50:1 for the first tank, 100:1 for the next couple) and crank up the oil pump. On the 800s, it's recommended to turn the adjuster rich another three turns or so. I'd do the same with the 600, maybe even go further while you're breaking in. I've never run Polaris blue oil, but I hear it's best for pre-mix and carbureted sleds, not so good for the newer CFI motors. There aren't many hard and fast rules for break-in; the only one I can think of is that it's hard to give it too much oil. You might foul a plug now and then is all.

 

[Troutfrea]

I'm not sure what's best, but I'd minimize the amount of Polaris blue you run. It's a lot thicker and will have a harder time reaching the rod bearings in particular. Ideally, you'd want to pre-mix some (I've heard 50:1 for the first tank, 100:1 for the next couple) and crank up the oil pump. On the 800s, it's recommended to turn the adjuster rich another three turns or so. I'd do the same with the 600, maybe even go further while you're breaking in. I've never run Polaris blue oil, but I hear it's best for pre-mix and carbureted sleds, not so good for the newer CFI motors. There aren't many hard and fast rules for break-in; the only one I can think of is that it's hard to give it too much oil. You might foul a plug now and then is all.

Thanks for your thoughts. I was going to go with blue based on the service manuals recommendation. I’ll call a couple of shops and get a couple of more opinions. I agree, you can’t. Get too much oil on these motors. I plan on doing just what you suggested, pre-mixing the gas for the first tank and turn the dial up on the pump.

 

[BeartoothBaron]

Yup. You may have noticed I'm doing a top end too. I'm giving Legend oil a try - that's technically not synthetic, and they say "no problem" on break-in, so I'll just run that off the bat. My plan is to mix 50:1 on the first tank, crank up the oiler (beyond its already turned-up setting), and run it in the "ethanol" setting initially. After the first tank, I'll back it down to 100:1, keep the oiler turned up until 150 miles or so, then back the oiler down, but probably keep adding a little oil to every tank of gas. Not that I'm any expert on break-in, but the common recommendations seem to be lots of oil and vary the throttle and RPMs a lot (up to wide open, but no long runs at WOT). Hopefully somebody can chime in on the Polaris blue oil. I don't think it'll hurt anything. I'd just minimize how long I run it, and there might be a better choice. I've done tons of reading on the "best" oils to run, but break-in is a special case where I haven't found much beyond "don't run synthetic."

 

[Troutfrea]

On second thought, I’m going with Polaris blue to start. I will only run it as long as I have to but feel it’s the right thing to do based on the manufacturer’s recommendations (for both my pistons and Polaris). It’s also what my buddy said to do and he worked at a dealership for about 10 years. I plan on cleaning the exhaust valves after initial break-in as I expect the blue to get them dirty. I’ll report back soon.

 

[Troutfrea]

Greetings, so it’s been about 100 miles after the rebuild and the sled is giving me problems. Holy cow is this frustrating!
Last year I ran it for about 30 miles and it seemed fine. We ran out of snow so I shut it down for the season. During the break in ride I was concerned/paranoid about not enough oil reaching the motor as the level in the tank didn’t seem to be going down fast enough for me.

Fast forward to this season and I installed a vented cap from Paaso. I also changed the oil from a synthetic blend (used during break in) to VES gold. This past weekend we had the sled out 2x and put about 30 miles per day on it (my 14 year old daughter is riding it). Yesterday, she went out with a big group of experienced riders and about 2 miles in it shut down suddenly. She said the temp was in the 130s. My buddy who was there said initially the clutch wouldn’t move but did after sitting for a couple of minutes. They added oil to the gas and put oil in each cylinder (through the spark plug hole) and rode it for 20 or so miles. He said the plugs looked clean with no signs of oil in the cylinder. There were also several air bubbles in the small oil lines.

I haven’t had time to break into anything but I don’t understand why the motor seems to be starving for oil. Per my previous posts, I’ve turned up the pump and I made sure all lines were blend at install. What are the odds my oil pump is bad? What else could it be? I don’t understand what is going on.

 

[ditch1000]

Check to ensure the oil lines are hooked up to the correct ports. I picked up a fixer upper with a blown top end and this was the case; the mag side cylinder and crank bearing lines were swapped. One crank later and figured out the oils lines and never had an issue after..