I'm rebuilding my 03 Vert. Escape 800 and was looking at top end kits, I've seen a few kits with O.E.M. style high silicia content pistons with skirts that are molybdenum coated and the piston top is ceramic anodized. Or should i go with forged Wiseco pistons? Another guy told me that the forged pistons don't heat up and expand as well as the cast oem style. Any feedback on what you guys are running would be great.

I would go with oem pistons. If you run wiseco but sure to let the sled warm up good before ripping on it.

There are pros and cons to each....

OEM pistons are fine for the masses and will last plenty long enough for a solid rebuild. They also have lower cost going for them, especialy if your old ones are fine.... Factory Hypereutectic pistons will run at tighter tolerences and will have less piston slap at start-up and have less thermal expansion. They can not, however, handle any form of uncontrolled flame propagation for any period of time.

Wiseco pistons are lighter ( I beleive) and manufactured to a tighter tolerance than mass produced stock pistons. They are stronger and more expensive. They require a minimum of .0045 piston to wall clearance, due to greater thermal expansion, or cylinder seizure WILL OCCUR!! I do not know of any dome differences but that would effect compression and thusly power production. There is the standard "M" series and the Pro-Lite series. I run the "M" series myself.

Check Ebay, for Wisecos, some times you can find a deal on them. I picked up a set for my 03 700 for $75/ Piston. It is also a good idea to run the Wiseco needle bearings with their pistons. They are wider in-between the pin saddles and the stock bearings might lend to an unstable piston/ bearing combination.

As with any engine, Piston ring gap should be checked, and set properly. Wiseco recomends a MINIMUM of .004" of ring gap for every inch of cylinder bore. On a 85mm bore, that is .0134". I set my rings at .018" Top and .016 bottom. This allows the for greater thermal expansion of the top ring due to its closer proximity to the chamber and exposure to greater temps. If you are running an aftermarket exhaust and additional mods, you might want to increase that. Factory spec with stock pistons is .016-.022".

you will need to have your jugs resized for wiesco.
which means replating the nikasil

That's nonsense.

I'd say......

Hey XCR, where you at?

East of Hayward, 23 miles.

not unles you over size.

i have ran both types in my old 440. got better life out of the oem pistons but a litle more compresion with the wiseco (only a couple psi) and they were cheaper.

thats the craziest thing ive heard on here, in my own experiance i have awesome luck with wiesco pistons. just one of my firends was trying to tell me to stay away from them so i wanted to get some second opinions. I did pick up a pro lite set and pin bearings

Can someone tell me the differances between the Wiseco M-series pistons and the Wiseco Pro-Lite pistons ?

I like the SPI's

The biggest downfall with oem Polaris pistons is their cost. Many guys balk at them when they see they can get 2 aftermarket slugs for the price of 1 oem. You get what you pay for. For a start it up and go guy, stick with oem.

I'm with Randy, the SPI's are great and a great price. I bought a pair off from ebay about three years ago and threw them in my 800 ves as preventive maint. at 8000 miles. It cost me about 140.00 to freshen it up and about 3000 miles later it runs great. I have also had good luck with wiseco. They did have a few issues back in the 70's and it is amazing how long problems of the past can stay with them. It is like saying polaris sleds are junk because the 79 TX-L had brake and chaincase issues.

Never had chaincase issues on my 3 TXL's. Edges are a different story