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Quote:

Originally Posted by gianni1951 (Post 124829)

Hi Kev,

in wich way you calculate the compression (from 10:1 to 11:1). I think that only a bigger bore don't change the compression. I think that compression is a ratio between the two volume (minimum for compression, maximum at the end of stroke). So, if you don't change the stroke of piston, according to me, you have the same compression independently by the piston diameter. Unless you have pull down the head (machining plane or changing gasket system).

Can you explain me ??? Tank you in advance.

Ciao.:hismiley::hismiley::hismiley::hismiley:

2 years ago I fitted a Raptor 700 JE piston kit which has a 2mm biger bore size but also a higher dome on the top of the piston to make the compression ratio 11:1.

http://cgi.ebay.com/ebaymotors/Rapto...Q5fAccessories

As Freez mentioned you can also lower the XT cylinder by machining it's base to get a higher compression ratio.