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Discussion Starter · #1 ·
So I have a '97 Zl 440 that blew a piston two years ago, we fixed it and have been riding it a little, maybe 300 miles since then. So the most recent thing started at about the beginning of this year. It would start okay at the beginning of the day, but if you ride it, then let it sit for an hour or two, it absolutaly won't start. I was on snowmobileforum.com and the guys on there said it had to be a crank seal, but I didn't think I could replace that, so I just let it be and rode it for about a month. Now I think I blew the same piston I blew two years ago and am assuming that it is the crank seal that started my problems two years ago. Could it just be the crank seal that is making it not fire on that cylinder, or is it for sure blown. It has compression of 120 on the pto, and 60 on the mag. So now I just ordered two new crank seals from my A-C dealer and they will be here wednesday. I have never been inside the crank case and would really like some step by step instructions to do this. I am willing to learn, I just need someone to help me. Your help is soooooo much appreciated, so please help me.
 

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Its not a very hard to do. Go to member 109jb he has a link for free service manual downloads. It has step by step instructions its a good thing to have for your rebuild and any other issues you may ever have.
 

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You want both pistons to be the same. Take a look at OEM, or SPI pistons.

In my experience if the crank seal fails the piston will not last long, possibly only seconds before the lean condition melts that puppy. I'd look to your intake flanges before the crank seals, especially if it is the MAG side with the problem, because the the MAG end seal is covered and protected, unlike the PTO end seal.
 

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That listing is for .010 over size and for one. Really should replace both in my opinion.

Hopefully others will chime in. Unless the piston is OE, I'm a little leery about replacing just one. Looks like SPI's, for the ZL440, many not be an E-Bay item.
 

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Discussion Starter · #12 ·
So my dad took it to a guy he knows that builds race car engines. Since there was a pretty deep scratch he is just gonna bore it out to the size of the scratch. He said what caused it is the cylinder is oblonged, because of the way the piston slides, they do get that way. That is why I have blew 2 pistons in 200 miles. So when he is done, get an oversized piston and off I go. Well and the crank seals too. What do you guys think?
 

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Dont bore those cylinders. They are nakasil coated. if you have a deep scratch just pick up a new cylinder. not new in the sense of the word, I would buy a replated cylinder.eichoffs has them for 215 with exchange or will rebuild yours to factory spec. I have 7 sleds and run nothing but spi pistons in them. I dont recommend wisecos because they are to finicky for the average rider.
 

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Discussion Starter · #15 ·
I found a used jug on ebay, I think I will go with that. I really cannot afford to get a remanufactured jug right now. The one I am looking at came off of a running 97 ZL, so I think it will be the best way to go right now for me.
 

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Like Mike said, a 2-stroke cylinder is not anything like a car engine cylinder. The cylinder bore is a very hard coating and if you bore it you have just ruined that cylinder in my opinion. Best bet is a re-plated cylinder like Mike said, or you may be able to find a good used one on e-bay.

If you have a bad crank seal it doesn't matter what kind of piston you have in there. Any brand will fail with a bad crank seal due to leaning out of the fuel mixture.

As for pistons, I run SPI and they are great. Buddies of mine have run Wiseco's in both stock and custom built engines and have had many problems. One of those guys eventually went SPI and has not had another problem. The other had a custom built performance engine from a reputable builder. He put 3 pistons in before the engine had 3000 miles. He eventually sold that sled and bought a brand new one. Meanwhile the rest of my riding group uses SPI or OEM and we never have problems.

My 2 cents
 

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Discussion Starter · #17 ·
Thanks for all the help guys, I ended up getting that piston and jug from the running Zl for $72shipped. I am happy with that, it may not be as good as a remaned one, but I am gonna change the crank seals and drop this used setup in and ride it. I guess if it blows in a year or two, I am only out $70 bucks and a little time. Stick around though, I will prolly still have questions on the crank seals.
 

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That sounds like a good deal if the cylinder is in good shape. I would atleast hone the cylinder and get some new rings. If its a cat piston SPI rings will work with it, make sure to check the ringend gap in the top, middle and bottom of the jug bottom being right below the ports. Use the piston to push the ring in the jug to make sure its square.
 
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