400ex Gaskets

[FBRacing76]

Hey guys I got a quick question. I bought a cylinder bored .120 which is the 426. It has everything but the gasket kit. It has 11:1 compression which is really to high for what I do. I've heard before you can get different gaskets to lower the compression? Is that true?

[cals400ex]

with the stock gaskets you definately won't be at 11:1. i have a feeling even with the thin ones you won't be a true 11:1. the stated ratios are usually off by a little bit from what i gather. yes, you can run the stock thickness gaskets. i would get the ones for the 426 bore too. call up c&d, they have what you want. however, the thicker gaskets raise the head farther away from the piston which means you get a flame travel that isn't as good across the top of the piston.

[j753301]

i thought only the wiseco piston werent right?i think with the stock gaskets there only like 9.5 to 1.i heard the je and ross pistons are a true 10.8 to 1?i hope so because im going to be ordering a ross soon.

[cals400ex]

i have been told the ross and je pistons are closer to the stated ratios. with the stock gaskets, they won't be. running thinner gaskets does make a difference with compression ratios. you can confirm this by checking with the compression ratio calculators. however, the je and ross pistons are made for the xr/ex bikes. they were designed for the xr bikes first, from what i gather. the xr has thin gaskets on from the factory. i also wouldn't doubt tha the companies fudge a little bit on the ratios, but that is my opinion.