i need a 92mm piston 11-13 to 1 4 a 400ex

[mntly_imptnt]

hey guys i am looking for a 92mm piston for my 400ex. i would like the compression between 11 to 1 and 13 to 1. sparks only has a 14 to 1 kit. i would appreciate any help. thanks

[MIKE400EX]

Take the 14:1 piston and either machine it or juggle the gasket thicknesses to get it down to around 12-13:1. 2cc's off the piston top should do ya.

[chad502ex]

hey mntly, I second MIKE recommendation on making head gasket thicker or shaving the piston deck to decrease comp ratio.

But if your a little too confused on the process on calculating compression ratio, Ross Pistons has an excellent "Calculator" to assist.

http://www.rosspistons.com/CR%20Calculator.htm

The only # that you probally don't know is head volume (in cc's). So, the stock 400ex head volume is 48cc exactly. This was determined and measured by my NASCAR machinist and was verified by me also (see my Tech Talk section on my website for more info).

Hope this helps.

:)

Chad502EX.com

[MIKE400EX]

Isn't the head volume 38 cc's?:confused:

[mntly_imptnt]

thanks guys these are options now, but i would still like to find a piston that is the right comp. i dont like the idea of a thicker head gasket. wouldn't it have some bad affects? thanks for the help. anymore options or info would be appreciated.

ps 91mm would also be acceptable.

[chad502ex]

Originally posted by MIKE400EX
Isn't the head volume 38 cc's?:confused:

Mike, yes your correct,... sorry I had a brain fart and said "48cc".

http://www.chad502ex.com/measuring_head.htm

Chad502EX.com