Compression Ratings by Manufacture, Real or BS?

[Quadzilla]

Ok guys, this one has been floating around for a while but I don't think that I've seen a clear answer on this so here goes the question:

Who's pistons (Wisco, JE, Ross) actually run at the rated compression rate with stock thickness gaskets for the 400EX? I *think* that I've read that the Wisco 440 pistons are actually the same as the ones used for an XR and using the EX gaskets lower the compression. I also *think* that I've read that JE and Ross run at true compression (as marked, i.e. 11:1) WITH stock EX gaskets.

Can somebody answer this? I am about to build a 416 or 425 kit (and will prob use a JE or Ross) and need to know what gastkets to get (stock EX thickness or stock XR thickness) to run at the advertised compression rating on the piston (in my case I want to run 11:1).

Thanks much!
Fred

[Quadzilla]

Bumpidy bump....

[400exdad]

Z, it is true that the advertised compression ratio is not with stock gaskets. There is a thread in the FAQ that goes into great detail in proving the "myth". The base gasket has a big effect on it as well. Something that you have to order from Cometic or leave out. Mickey Dunlap talks about it in his FAQ too. After you do the calculations, you'll realize that a bunch of folks don't do the gaskets correctly when they drop in that high compression piston and that's why their quad doesn't ping or detonate more.

Go here for some good reading:

http://www.exriders.com/vbb/showthread.php?s=&threadid=48435