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Discussion Starter · #1 ·
I'v looked at pictures and what others have said about how to read a blown piston to find the cause.
this is what I found when I pulled the piston out of my sks
the intake side skirt is scarred, multiple lines across a 2" span, from my understanding this is from lack of oil
the crown broke on the intake side, from what I'v read this is caused by a leaking head gaskit? this also could have been the cause of the lines on the skirt, however the line arnt deep.

the exhaust skirt has similar scarres as the intake side

and I found both wrisp pin clips imbeded in the top of the cylinder, what could cause these to come out of the grooves?

Im trying to figure out what caused it to blow the mag side again, after just 32 miles.. I had just replaced the cylinder, piston, wrist pin, and bearing.. all head gaskits.. and dont feel like throwing more money at it just to have it blow again (going to rebuilt top and bottem this time around)

Im thinking it may have been caused by a faulty oil pump?
 

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I thought when the oil pump goes it would dump excessive amounts of oil into the engine/carbs? Never had one fail, but thats what Ive been told happens.
 

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wrist pin clips don't usually leave their holding place. Did you put the opening at 12 or 6 o'clock? Were they seated correctly?

A picture is worth 1000 words...
 

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When you have issues like this you need to have pics and from the pics really wont help because if you only have 32 miles on the pistons that means you might have ingested something or when you put your motor back together there might have been something that you left in the motor or missed. I will help you out the most I can. Now there is ways that you can break in a motor and there is a lot that you can do to rune them. If you have any question please PM me and I can go over on how to break in a motor if you don't know.
 

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Discussion Starter · #6 ·
When I put the clips in I had the opening at like 3 o'clock. they were both all the way in the groove.

as far as breaking it in, I did it just like the xc I rebuilt earlier this winter, let it idle for about 10 min, shut it off let it cool and retorqued the head, then told my buddy to take it easy. which he did, I rode with him for most of the day and I doubt he ever hit full throttle.

I will get pictures tomorrow.
 

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Thats usually the problem, letting your buddy ride the sled on a fresh re-build. [Disappointed] ha, j/k probably wouldnt matter who was riding it.

Just a few things, you never told us if that cylinder had any work done to it the last time you were in there. Maybe the cylinder wasnt in spec and thats why didnt last. So, was it honed or bored, did you have it measured?

What happen on the last failure? I dont know the history of your sled or what caused the last blow-up but, might be related in some way..?

Sounds like everyone is agreeing that the clip was installed wrong.
 

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Discussion Starter · #9 ·
when I got the sled it had a toasted mag side. I replaced the cylinder with a good spare I had.

I took a closer look, only one clip came out. Im having second thought on rebuilding it, I already have about $800 into it now and dont want to invest to much money into a 13 year old sled. Im considering parting it out.
 

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first problem is you didnt figure out what caused it to blow the first time around. you simply put it back together. thats why that cylinder blew withing 30 miles.
 
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