[akheloce]

So my sled was running kind of boggy, acting like the carbs needed cleaned, so I took it into my shop to take a look at it. Just for the heck of it, I ran a compression check, and the PTO side was about 125 (a little low I thought), and the mag side was only 75 lbs.! so I pulled the head off and took some really crappy pics with my cell phone of the low compression (mag) side.

I know I'm into it for a new set of pistons and rings, and at least a good honing, but what do you think caused this? Or was this even my problem? It has always run a little fat, with 500 mains, and generally black plugs.

 

[mxzwfo]

The bottom picture. Is that bad spot on the exhaust side or the intake side?? Post some pics when you get them out.

 

[akheloce]

The bottom picture. Is that bad spot on the exhaust side or the intake side?? Post some pics when you get them out.[/b]

The top pic shows the edge @ the exhaust side. Both pics were taken from the same angle, so the bottom one is in between the two.

It will be this weekend before I can get them out, so I'll get some more pics then.

 

[wickedfast340]

it looks like you got a burned piston on your hands



if it was on the exhaust side, it is prolly due to excessive heat. I would check for a vacuum leak or something, causeing it to run leaner and melt your piston.


this is very hard to believe if your running as fat as you are, and your plugs are black.


is there any pitting in the piston or head? i couldnt tell from the low res pics. maybe just a ring came apart and jammed in your exhaust valve.

a new piston and rings is in order, let me know how things go

 

[akheloce]

this is very hard to believe if your running as fat as you are, and your plugs are black.[/b]

This is just a guestimation, but I think it was running fat right up until it wasn't. I havent gotten to the carbs yet, but I have an idea that it may have been partially to blame. (jet clogged up?) It has historically run pretty rich, but I didnt want to jet it down until I got some gauges. I wasn't riding it when the symptoms first showed up, so I didnt get to see the plugs after they came out. My friend was on it, said it started running like crap, so he threw another set of plugs in it... still ran like crap, so he took it straight home. The next week, I drained the fuel, put seafoam in it (no time or tools avail to clean carbs). I ran it for about 2 miles, and it still didnt clean up.(we stopped, because my brother's 04 summit died and wouldnt restart... my sled ran like crap, but was able to tow him home). I pulled the plugs, and the PTO side (good) was a little lighter than usual, but nothing to worry about, the mag side was a wierd shade of light gray that I hadnt seen before. I stopped there, and decided to clean the carbs, and check the reeds (V-Force, installed 300 miles ago) before I went any further.

There was a little pitting on the piston dome, and some carbon build up (kind of hard to differentiate without cleaning it up), and there was one spec of metal on the head... at first I thought it was a tool gouge, but I scraped it with my finger nail, and it flaked right off (like a small drop of solder that landed on it). The good side had black carbon on it, and the bad side was pretty clean (other than the metal flake).


I guess it's all just speculation until I can dig deeper, and get more information.

 

[wickedfast340]

the light color gray on the plug is due to overheating. that cylinder on the sled was running way to lean. I bet you got some crap in your carbs, and it leaned out, or a vacuum leak caused it to run lean, and it melted your piston. the flake you found was either part of the piston or ring. the pitting isnt good, that tells you your piston came apart a lil.



take motor out of the sled, new pistons and rings(maybe a good hone?) and clean carbs and throw back together.

before you do this, put the motor together, and do a leakdown test on the bottom end to check the seaqls for leaks. hopefully you just got water in your mainjet.

my dad had a 583 that this hapened to. he had a lil water in the carb, and it caused the mag side cylinder to melt down. his sled only had 1500 miles on it, and it was running great and a lil rich

 

[labudda]

thats not a burn down... this is a burndown

[attachment=33096:burn.jpg]

this all happened in about a 1/2 mile as far as I could tell.

 

[Thumbdoctor]

thats not a burn down... this is a burndown

[attachment=33096:burn.jpg]

this all happened in about a 1/2 mile as far as I could tell.[/b]

Budda,
How'd you get that piston out without removing the head LOL.

 

[trailblazer]

He took it out the bottom end Simon. :lookaround:

Did this happen this year Matt?

Or was this what happened in Cochrane last year?

Cody just cold seized his nicely rebuilt motor.

Back to the drawing board. Or the garage.

I'll post some pics once I get some time.

Jeff

 

[labudda]

that was from last year in cochrane. Stinks about the cold sieze Jeff, time for the garage. And Simon I am a magician :wink:

Right after the rebuild I took a pic, that piston is now my pen/pencil holder in the garage

 

[Thumbdoctor]

that was from last year in cochrane. Stinks about the cold sieze Jeff, time for the garage. And Simon I am a magician :wink:

Right after the rebuild I took a pic, that piston is now my pen/pencil holder in the garage[/b]

Ahh, so your a magician Matt. Why don't you pull a rabbit out of a hat and make a new mod 600 short block appear in Cody's sled.

Too bad about the motor Cody...Jeff.

Cold seizure for sure or 4 corner. I've never heard Bill's cast pistons do that. Wisecos are renown for cold seizing if you don't get the sizing right but you have to bear with cold piston slap which for some is quite unsettling. Maybe you can clean up Cody's pistons and make pencil holders and raffle them here or Ebay (stranger things have happened).

I'll start the bid at $10.00 CDN for an "experienced" piston/pencil holder.....

 

[trailblazer]

Hi Simon.

No we're not sure.
Just assuming based on what we found inside and pics that someone else had posted on here before.

I'll start a new thread in General Snowmobiling and post pics in there.
I don't want to hijack this thread.

Looking forward to your expert opinions and experience.

Jeff