I'm in the process of rebuilding the top end of the wife's '98 SP500.

From what I have found - my piston options are either Polaris or Wiseco. The Polaris piston comes in .010 and .020" and I can put together a pistion "kit" for about $10 less than the Wiseco. The Wiseco comes in .020 and .040".

Which one would you use, and WHY??

PS - I have an HO camshaft and carb that is going on it.

 

I would go with the Wiseco. I don't know who or where the Polaris pistons are made. I know Wiseco exceeds the OEM specs when they build a piston. They are a piston maker. Polaris is not. I'm sure the factory piston will do the job, but for the $10 I would get gauranteed quality.

 

If you go wiseco make sure it is bored by a someone who knows wiseco pistons. There tolerances really need to be just right in the cylinder for the piston to work its best. I personally would go with the .01 from Polaris just to save more for a future bore. Polaris does not go cheap on their pistons, if they did they would be eating more warranty work. Just my opinon on it. You are not going to get any noticable gain from a bigger bore without some other work being done so go with the smallest bore you can go with. Jay

 

A wiseco piston is a forged piston while the polaris' are cast.The wiseco is by far a superior piston than the ones polaris sells.I have been told that with a polaris the skirts on the piston tend to crack or break and the fix for this problem is a wiseco.

 

Don't get me wrong I am not arguing the value of Wiseco they are a much better piston. The difference in manufacturing is why I said have your cylinder bored by somebody that knows Wiseco. The Piston expands differently then the stock piston. I guess at a $10 dollar difference Wiseco would be a good bet but I am always conservative when it comes to boring cylinders. As for Polaris pistons some do have problems but they are rare. It will depend on how the machine is used. Unless your wife is a crazy woman on the thing the Polaris piston is more then enough.

 

I thought the cracking skirt problem was limited to the 2 strokes due to the long thin skirt required?? A 4 stroke pistion is pretty much a "chunk"

 

That very well may be. Did you take yours apart yet?

 

Yep, its apart - the old piston has very little scuffing, cylinder wall is smooth as glass, rings are worn (been using a little oil for the past 2 years - since I got it) - the camshaft went out, so I'm just doing a top end and cam chain while I'm already in it. I have not mic'd the cyl yet - I'm pretty sure I can get away with a .010" over, but would probably feel safer with the .020" over. I'll know for sure once I mic it.

It has 4800 miles, and we have put 3100 of them on it.

I'm just trying to get opinions of WHY I should go Wiseco over Polaris.