More Compression & CC's

[Blown 331]

If I go with a 12 to 1 piston can I still run on 93 octane? I think stock compression is 10.5 to 1 and the CRF is 12 to 1 and runs on pump gas. Anyone know of a big bore piston? I heard of a 500cc kit but I can't find it.
I would like a 12 to 1, 500cc piston if it will run on pump gas and if there is one avalible. Anyone know?

[2004TRX450R]

Yes there is a 500cc piston. JE makes it. I'm not sure of the compresson on it though. I know they make either an 11;1 or 11.5:1 and a 13:1 in the stock size piston but I can't recall what the compression was on the 500cc piston. You will have to have the cylender bored and replated wich will probably cost in the $250+ range on top of the piston at probably another $200.

[Bretmd94]

I would run a mix of 110 and 93 wiht a 12:1 piston. Maybe half and half. Thats what i did with my old raptor when i put it to 11.5:1. The jetting gets confusing with race gas but once its figured out it should run awesome. I would say that there will be a high chance of some upper end noise with just 93 oct. The race gas mixture will make your motor a lot more happy and sounding better.

After you get the piston test it out a bit with different types when re jetting.

[#1speedbump]

Je , Sparks, Duncan, And FST all have kits that will put you into the 500 cc area. I believe Duncan is the only one that offers theres as a kit with more than just a piston but not positive. Also the Honda is 9 or 9.5:1 not any higher. Hope this helps

[2004TRX450R]

Stock comp is 10.5:1. Just confirmed it in my service manual. I was just talking with a guy at work a couple days ago and he was telling me you are supposed to run regular unleaded with race gas when you mix it because there is less additives in it. It is supposed to make more power and work better that way.

I belive JE makes the pistons for Duncan. I know when I was calling JE awhile back they said Duncan was haveing them make pistons for them.