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Hey I just picked up a 94 sport sks and was checking out the engine and noticed the engine has a tag that is EC44-2PM-4100 the heads and the cylinders are labeled with EC44-3PM I'm gonna need some new pistons and rings and am trying to match them with my engine not sure what # to use .. also with yellow paint it's written +20 on cylinders and top of pistons
 

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+20 or .020 oversized should mean it has been rebuilt already with bigger pistons and that the cylinders were cut to accommodate said larger pistons and rings. Which means you will need to go back to said size pistons or go even larger which would mean the cylinder will need to be bored out to match said new pistons.

Why are you rebuilding it? Low compression?

The Indy Sport is a fan cooled sled.

This piston from MFG Supply is what you would need plus all the gaskets and what not. Tbh I don't know if you could even go bigger the .20 oversized on those cylinders as they were not very thick to begin with iirc. You very well may end up having to go to eBay or a swap meet to get a new set of cylinders as well, unless of course they can be cleaned up enough.

https://www.mfgsupply.com/snowmobile/snowengine/snowoempistons/oemsnowpistons/oemsnowpolpistons/09-710-2.html

I would also look at SPI as well.
 

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+20 or .020 oversized should mean it has been rebuilt already with bigger pistons and that the cylinders were cut to accommodate said larger pistons and rings. Which means you will need to go back to said size pistons or go even larger which would mean the cylinder will need to be bored out to match said new pistons.

Why are you rebuilding it? Low compression?

The Indy Sport is a fan cooled sled.

This piston from MFG Supply is what you would need plus all the gaskets and what not. Tbh I don't know if you could even go bigger the .20 oversized on those cylinders as they were not very thick to begin with iirc. You very well may end up having to go to eBay or a swap meet to get a new set of cylinders as well, unless of course they can be cleaned up enough.

https://www.mfgsupply.com/snowmobile/snowengine/snowoempistons/oemsnowpistons/oemsnowpolpistons/09-710-2.html

I would also look at SPI as well.


The compression was a little low so I cracked it open to check what's going on and the pistons are a bit scored . Do you know why the plate on the lower would have a different engine number then the cylinders and heads
 

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The cylinder is one piece design also known as mono-block same with the heads. And it can happen, it could be what factory had sitting there or it could be that someone changed out the cylinders/head already. Either way it doesn't make a difference as they are the correct cylinders/heads that should be on there.

IF you knew what kind of pistons were already in there you could just order a piston ring set, hone out the cylinders and replace the gaskets that you need to replace and go from there.

Also what was compression exactly on each cylinder?
 
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