What happened to my crank?

Octanee · Jan 26, 2017

Hey guys, So I picked up a pro rmk that went down last weekend, guy said cruising the trail and it started to sound bad and he let it idle down then it shut off. I pulled the jugs, the pistons had some scuffing, i was hoping for it to be a piston issue, but I see one of the connecting rod mains on the MAG side perhaps lacked oil, It got hot enough that its dry like theres no oil at all, however the wrist pin feels ok and the bore has that sticky oil feeling to it. the clutch side is OK. Sled has only 1700km on it.

Would Could It be that the "infamous" oil cap issue occured? but I'd think both would look dry? and oil pump, well it should be dry both sides again right? Maybe a plugged oil spray jet? or 2 somehow?. or maybe just a literal rod main bearing failure which caused it to get hot enough for the oil to just disintegrate? It still spins over just fine however its STIFF, no chunks or looseness otherwise.

Also that cylinder has some sidewall scuffing from the fine particles, but doesn't feel like any roughness, maybe some muratic acid and a re-honing to fix that?

<img src="http://i.imgur.com/76P4VYM.jpg" width="500" height="500">
<img src="http://i.imgur.com/Irujr4O.jpg" width="500" height="500">
<img src="http://i.imgur.com/r2Sjcq3.jpg" width="500" height="500">

Sheetmetalfab · Jan 26, 2017

Octanee said:
Hey guys, So I picked up a pro rmk that went down last weekend, guy said cruising the trail and it started to sound bad and he let it idle down then it shut off. I pulled the jugs, the pistons had some scuffing, i was hoping for it to be a piston issue, but I see one of the connecting rod mains on the MAG side perhaps lacked oil, It got hot enough that its dry like theres no oil at all, however the wrist pin feels ok and the bore has that sticky oil feeling to it. the clutch side is OK. Sled has only 1700km on it.

Would Could It be that the "infamous" oil cap issue occured? but I'd think both would look dry? and oil pump, well it should be dry both sides again right? Maybe a plugged oil spray jet? or 2 somehow?. or maybe just a literal rod main bearing failure which caused it to get hot enough for the oil to just disintegrate? It still spins over just fine however its STIFF, no chunks or looseness otherwise.

Also that cylinder has some sidewall scuffing from the fine particles, but doesn't feel like any roughness, maybe some muratic acid and a re-honing to fix that?

<img src="http://i.imgur.com/76P4VYM.jpg" width="500" height="500">
<img src="http://i.imgur.com/Irujr4O.jpg" width="500" height="500">
<img src="http://i.imgur.com/r2Sjcq3.jpg" width="500" height="500">

What year?
Looks like a lower rod bearing failure.
If it was at higher rpm it probably would have broken a rod. (I've seen it)

Detonation can tear up the bearing.
Especially combined with a lean oil condition.

Octanee · Jan 27, 2017

Sheetmetalfab said:
What year?
Looks like a lower rod bearing failure.
If it was at higher rpm it probably would have broken a rod. (I've seen it)

Detonation can tear up the bearing.
Especially combined with a lean oil condition.

It's a 2013, I'm new to these pros but i noticed that yellow timing key plug thing, It was on the regular/ethanol fuel one, I swapped it over to the premium one. Pistons dont really show any detonation ontop of them or pitting as far as I can tell. But she did look perhaps a bit lean in overall color of exhaust I'd say, but who knows with the fuel injection

kooter353 · Jan 27, 2017

Yellow timing key plug? Where did you find this? I understood that the only way to switch from Ethenol to premium is in the electric gauge pod?

omernikski · Jan 27, 2017

2012 dual fuel selector plug

kooter353 said:
Yellow timing key plug? Where did you find this? I understood that the only way to switch from Ethenol to premium is in the electric gauge pod?

Behind the oil tank on 12+ models is ia dual fuel selector plug

gtwitch · Jan 27, 2017

How many miles on the sled?? Sounds like Oil Pump was set too Lean (Polaris set many engines lean in these years and the Mag side was running hotter (alternator stator heat) and just enough lean to cause this. I had my 11 PRO 800 do this at about 3200 miles and after the rebuild I turned the oil pump up so the mark was at the top of the V (rich side) and I think the fuel/oil ratio is 45 to 55 :1 now. When my PRO went down (late Feb 2015) after a 80+mile ride and 2 miles from trailer) it just made noise and slowly seized up and after it cooled down, it would pullover easy but I towed it to the trailer. The Mag side crank journal and rod bottom end looked same as picture. Fixed it with rebuilt crank and SNO-X piston /Fix kit and it runs fine now with about 1600 miles at this time.

gtwitch in wyoming

Octanee · Jan 27, 2017

Supposedly only 1700,km on the machine. I'll bet just too lean on the oil, I'll replace and crank up the oil injection, even 45:1.is too lean imo, I'd go like 35:1 or 40:1 at best.

geo · Jan 28, 2017

Worst thing you can do with these is "cruising the trail ". Especially the '13's stock.

Low rpm, little throttle pulling equals little oil. Antique system now that has to be over compensated for and that is against EPA regs lol. A couple of short braps sucks up any puddle in there and light cruising isn't enough to put any extra back in for the next "brap brap".

My '13 was turned up max on the pump adj. screw from new. It's average oil consumption has been 32 to 1 so that means extra all the time. Smokes a bit at idle as it should being the antique it is.
And,,, I did the oil cap thing right away too.

Scott · Jan 28, 2017

geo said:
Worst thing you can do with these is "cruising the trail ". Especially the '13's stock.

Low rpm, little throttle pulling equals little oil. Antique system now that has to be over compensated for and that is against EPA regs lol. A couple of short braps sucks up any puddle in there and light cruising isn't enough to put any extra back in for the next "brap brap".

Yep...always vary the throttle. Long steady throttle is bad for a two stroke.

bustamove · Feb 7, 2017

Oh man exact same thing happen to me same scenario and everything mag side went on my 14. I bet 20 bucks you have an air bubble in your mag side rod oiler tube. I did. Was it the oil cap not venting? It did go whoosh when I opened mine. I dunno. Or bad fuel batch.....

I put a ski doo oil cap, turn up the oiler (not sure on turns). And running 100:1 oil in tank. And rk tek pistons. Hoping for the best

Octanee · Feb 7, 2017

bustamove said:
Oh man exact same thing happen to me same scenario and everything mag side went on my 14. I bet 20 bucks you have an air bubble in your mag side rod oiler tube. I did. Was it the oil cap not venting? It did go whoosh when I opened mine. I dunno. Or bad fuel batch.....

I put a ski doo oil cap, turn up the oiler (not sure on turns). And running 100:1 oil in tank. And rk tek pistons. Hoping for the best

100:1 is way too lean, I never noticed an air bubble, but Im going to guess that running at like 100:1, possibly the vent not venting, and 1700km caused it to go toast, on another forum a member said that it looked like the rings are worn out and leaking exhaust/compression, so yeah... :\ I have yet to vent the oil cap. I'm just going to drill a wee hole in it. and call it a day for the sled. I bought it with the blown engine so now I'll take care of the rest.

I turned up my oil injection screw until the head was flush with the nut. which on the pump's body puts it on the lower < which is richer. last ride out, never touched the vent but it did only light trail riding for 30km. consumed approx 200ml, and I'd guess ~8L. I want at leanest, a 40:1, these are a 2 stroke engine and it's not a special one like the doo etec, there for it needs oil like any other bike.

MKULTRA · Feb 7, 2017

He said 100:1 in the tank, plus the injection system.

Also if you drill the cap it will leak when on side or rolled over. Idk but it sound risky to me. Skidoo oil cap is like 25 bucks and have better venting.

Pro-8250 · Feb 7, 2017

MKULTRA said:
He said 100:1 in the tank, plus the injection system.

Also if you drill the cap it will leak when on side or rolled over. Idk but it sound risky to me. Skidoo oil cap is like 25 bucks and have better venting.

^^^^^^^
What he said.

Vincenthdfan · Feb 7, 2017

http://paasoracing.com/shop/polaris/vented-oil-cap-polaris/

I use these...they are very high quality and fool proof.

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What happened to my crank?

Octanee

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Sheetmetalfab

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Octanee

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kooter353

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omernikski

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gtwitch

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Octanee

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geo

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Scott

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bustamove

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Octanee

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MKULTRA

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Pro-8250

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Vincenthdfan

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