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06 drz 400s high compression help!

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i have a 2006 drz400s pretty much stock. the rings went on the bike so i was rebuild it and had a shop order me piston and valves. i have just round out that the piston is a 13.5 to 1 ratio and im not trying to run race gas as this is my daily driver. i have a stock cosmetics gasket set. i was wondering on how to drop the compression enough to run 93 octane????

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You should ask if the compression is 13 to 1 with a single layer or 3 layer base gasket. A 3 layer S base gasket my be all you need to drop it to acceptable level.  To drop it more than a gasket will do means machining material off the top of the piston.  To get exact compression ratio requires "cc"ing the combustion chamber with piston at TDC and calculating CR using the total sweep volume of the cylinder (cc plus sweep/cc)  Example: (40 + 400)/40 = 11.

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this is the part number for the piston it is already installed. wiseco 4714m9000. supposed to be a 13.5 to 1 and i have a single layer 400 base gasket. am i able to run a double layer and still get around 12 to 1? 

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