[Pistolpete102]

Hello everyone, I am new to the forum and snowmobiling. I recently purchased my first snowmobile, a very used 2004 Polaris RMK 600. I have been running into a problems and looking for answers led me to this forum. I originally bought this for ice fishing but then started to be more interested in snowmobiling. I am hoping some of you with a lot more experience than me could help me trouble shoot and see what ideas you have.

The first time I ran the sled it died a few miles in, turns out the carb bowl trap hose was bent which led to a crack and fuel loss. I fixed this and took the opportunity to clean the carbs. In doing this I managed to break off the fuel screw needle tip, unknowingly. I rode the sled about 40 miles or so in this condition, until I realized what I had done and had to get a different set of carbs from a similar sled.

The sled also had no top end power, both the exhaust bellows were torn. I replaced these and cleaned the valves. I noticed that one of the valves threads were completely stripped from the nut that holds the bellows, so I replaced that valve.

After fixing the exhaust valves I went out for a quick ride. The top end problem seemd to be fixed, but I did not get very far. My sled died and I could not figure out why. After getting a quick tow to a nearby parking lot I continued to try to start my sled. I pulled it a bunch of times, with the throttle depressed a bit for a lot of them. Then I noticed the main wiring harness connection was loose, the locking clip was broken. I pushed it back in and then the sled started up and ran for the mile back to my house.

The next morning I smelt a ton of gas in the garage so I pulled the plugs and turned it over. Gas shot all the way to the ceiling out of the mag side spark plug hole. While cleaning this up I noticed metal shavings! I was thinking they were the threads from the exhaust valve, but I checked with a magnent and they are magnetic. The valves I have are aluminum, the bellows nut is as well. This led me down the path of taking the head off for inspection.

The mag side piston head has some mashed up indentations and there are some really fine particles pressed into the mag head but it does not seem to bad. From reading other posts, it appears the steel is likely crank bearings or seals.
Looking into the crank from the mag side I did find some fine steel pieces, but I was thinking based on the size of pieces that may have passed up into the cylinder that I should be seeing a lot more visible damage indication if it was a crank bearing or seal. The biggest pieces were the ones in the cylinder, the ones in the crankcase were much smaller - I would think there would be a lot more in the crankcase if that where they were coming from?

My main goal is to figure out what the root cause of this is and what damage needs to be fixed so I dont end up continuing to damage the engine. I am thinking there was probably a lean condition from when I had the pilot circuit plugged....not sure if that caused this problem or if it is just a coincidence. I took some pictures, the mag side piston was much lighter than the PTO side piston, I am not sure if this was from running lean or having gas sitting in it cleaned it up?
EDIT: In these pictures I had already cleaned up the mag side piston head, it was a bit lighter than the PTO side but not this much.

I dont want to split the crank case if I dont have to, but it seems like maybe thats what needs to be done. I would really appreciate any advice or ideas anyone has. The couple rides I did get in were enough to get me hooked on snowmobiling, and I want to get back out riding!
My dilema is that it looks like it would be about 200 bucks or more so in tools to get the primary clutch and flywheel off, and if the crank is bad im not sure if it would even be worth replacing at this point.

Thanks for reading and thanks in advance for any ideas or comments! Looking forward to learning more.

Peter

 

[Pistolpete102]

I didnt think the cylinder walls looked bad. I got a gasket set and new rings, do you think this piston is usable?

before I opened it up compression was 90 psi both cylinders, but it was a loaner gage from AutoZone not sure if those work well for these engines.

 

[Pistolpete102]

Thanks for the replies BC_Dan and Kccats. I took the pistons off to see into the case better. I noticed more metal shavings so I am going to open it up this weekend and see what is going on.

 

[Pistolpete102]

I got the engine out of the sled and got the recoil housing off. I noticed similar metal pieces at the bottom of the housing and under the flywheel. Since there are pieces both in the crank and in the housing it seems like it’s likely the mag side crank seal. That would be the best case since it’s a straightforward swap.

I am waiting on a flywheel puller to arrive before I can Split the case.


what do you mean by porting?

Peter

 

[Pistolpete102]

Yes I think I will wait for that, I will be happy if I can pull this one off for now

I do have a heavy duty puller on the way, only because against my better judgment I tried one of the 30 dollar ones. It looked ok but the problem was it wasn’t thick enough so only about two threads were in when it started making contact…..stripped out pretty quick.

 

[Pistolpete102]

Well I finally got the heavy duty puller in the mail and it made quick work of pulling the flywheel! I got the cases split and found out 3/5 of the crank bearing were rough. The two middle ones were really bad as well as the mag side one.

the 600 uses a cross shaft to power the oil and water pump, I noticed oil coming from the weep hole. I’m wondering if this led to the bearing failure? Is it typical to find metal fragments from bearing failures in the crank case?

I decided to get the crank rebuilt even though it costs about what I paid for the sled! I might be able to find a used engine for the same price, but who knows what problems that one could have. I figured it it ends up getting me though a couple seasons it will be worth it. Looking forward to doing the engine rebuild once I get it back!

 

[Pistolpete102]

I am having the crank rebuilder do that part as well, I was going to do it but I did not want to risk messing it up and having problems with a newly rebuilt crank 😂

 

[Pistolpete102]

I got the crank back and got the case sealed, pistons, and cylinders on yesterday. Not to much left now.

When I pulled the stator I took the whole stator off the backing plate, I did not realize the whole thing came off. In doing so I took the small screw holding the two small wires to the backing plate and did not take a picture. I am pretty sure both of those wires go to the same screw to hold them to the backing plate, but not 100%....wanted to see if anyone knows if that is right or if they go to different locations? Theres only one small bolt but wasnt sure if one of them goes to something else or hooks on to another screw, I cant remember. I looked at the wiring diagram but its hard to tell with the internal stator wiring.

Heres a picture of a similar stator and it looks like both the wire rings are on the one screw. Thanks in advance.

 

[Pistolpete102]

I found out that the two rings both go to that screw, lesson learned on taking pictures of everything when taking it apart.

I finished the rebuild and am finishing up getting everything together in the sled. The last thing I need to figure out is what to run for oil when breaking it in.
I had a full oil reservoir with Polaris VES oil so I primed the pump and main line with that.

I read a lot of other posts where people are recommending non-synthetic oil for break in. I could run this in the tank - but would that be a bad idea since I would be mixing it with synthetic from the pump?

 

[Pistolpete102]

Thanks BC_Dan and Coolhand.
Got everything put together and broke the rebuild in this weekend, it ran great! Much more power than I had before.

only thing I noticed was a high idle hanging for a few seconds when I came off throttle. I looked at some other posts and sounds like it’s probably running lean for the pilot circuit.
It was not close to engaging and was only for a few seconds so I might just wait and see how it goes before I adjust.

it was great to get out on one of the last few weekends of the season and not have to wait until next year! Now looking forward to doing some more riding after all this 😁

 

[Pistolpete102]

I am confused on how the tps calibration works on these carbs. I think I have it set ok but I don’t really get how it is supposed to work.

Everything I see for people doing this looks at the full throttle voltage, some reference the idle as well. The service manual calls out setting at slides fully closed and then using the idle screw to set the idle to a voltage.

I calibrated at full closed to the spec voltage, but when I adjust this to the specified idle voltage it is not open far enough for the sled to run at idle. Then I’m also over 4.0 volts at full open?

I guess what I’m getting at is you can only calibrate one set value at a position and then you get what you get at the other positions?

 

[Pistolpete102]

I should add I just left it calibrated at full closed and adjusted the idle as needed to get spec rpm, and it is running fine I am mostly just curious on the right way to do it.