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Discussion Starter #1
Just picked up three new piston kits on ebay (piston, rings, wrist pin) for......get this.......$50!!!

They're Parts Unlimited .020" over. I think that bumps my XLT SP from a 597cc up to a 607cc? Anyone have any idea how many more hp that would be? I know its not much, but just the fact that I got three band new whole piston kits for only $50 is AWESOME! I think the boring out of the cylinders will actually cost more ($35/cylinder which should include port chamfering (sp?) and polish).....ballpark?
 

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Discussion Starter #3
I can't wait to get em' in and have this completed......once and for all! I just did this last year, and I thought that was going to be the last time. Just goes to show, when doing a rebuild, you need to check EVERYTHING!

Unless of course you're feeling lucky. [;)]
 

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Practice makes perfect and owning a 97 XLT give you plenty of that. I'm just thinking how much I will appreciate my next sled since I had so much trouble with the first one.
 

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the HP increase from the increased size is maybe 1 HP, probably not even. The major gain is having good compression again, and having a good sleeve/ring fit.

-Dean
 

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Discussion Starter #7
Yeah, that's about what I figured too ripperd. I checked the compression this last spring and had 115 pto 115 center and only 100 mag. Thats with new piston and rings installed last fall. So this leads me to believe the cylinders may be out of round. Stock compression shouls be between 120 and 125 I believe? Boring them out to .020 should solve that.

Your right alaskangold.....ebay definately rules! [:D]

I can tear that engine down and build it back up in record time now Polaris XLTSP! I'm hoping this will be the last for some time. After I'm done with it, it goes to the wife, so it will still be my responsibility.
 

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I agree with Ripperd that the bigger pistons probably don't add as much as the fact that you have a trued cylinder and new rings, hence better compression. What I was told made my sled run so much better is the work that I had done on the ports. The guy who did my engine rebuild said that the XLT engine had some very bad machinining around the ports, the edges very sharp and rough and in his experience a little smoothing as well as the lighter mass of my 3 Wiseco's is what made my sled run a lot better, no longer any low end bog. That in addition to all the usual things like all carbs being perfectly synched, clutch cleaned and adjusted, etc, etc, etc...
 

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Discussion Starter #9
So did you actually have your cylinders "ported and polished" or did he just clean them up a bit?

Also what did he charge for that procedure alone?

I've always been under the impression that "porting and polish" ment removing a fair amound of material around the intake and exhaust ports to make them larger. Is that correct?
 

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He just cleaned them up a bit, because having spent many years working at the local Polaris dealer he had seen the rings actually get caught on the sharp edges of the port they were so bad from the factory. Jerry didn't charge me any more for doing it as he was doing a complete rebuild for me anyway and just figured it was part of doing a good job. I do know that my sled now runs a lot better than a stock XLT.

Porting is the process of matching the size of the intake and exhaust ports to the intake and exhaust manifolds for maximum air flow. At least that's what it is in the 4 stroke world which I am more familiar with. This is different from re-porting which is actually moving and changing the size of the ports in piston port engine for specific applications such as drag racing or when you go to significantly larger pistons which changes the stock porting.

I'm sure someone will jump in here and help us out if I'm wrong with all the experience we are lucky to have on the site.
 

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Discussion Starter #11
Great, thanks for the info! I'll be sure that I have the ports cleaned up as well then.

This is definately the best site I've come across yet for actual sled tech info!
 
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