11:1 or 12:1

[quad4life]

If I decide to swap pistons during my gasket leak repair, what do I lose by going from my current 12:1 down to 11:1, or even 10:1? I have not been running race gas (forgot, and I haven't had the bike long)) and it was pinging like crazy last weekend. I love the power I am currently getting. What will I notice most by going down on my compression?

[smorris1]

Your bike will actually run better with a 11:1 because it wont be pinging and stuff. With a 12:1 race gas is a must espacially with the 400ex engine. If you ran race gas with the 12:1 you would notice more torque and acceleration.

[bjg696]

With steeping down on the compression, that will be a good bit of noticeable power gone. But if your running unleaded gas with a 12.5:1, then a 11:1 will run like a top. Just like smorris said, with a 12.:1 with race gas will be a load of power. so its ur call...

[quad4life]

Well, I will be stepping down, so to speak. to 11:1 I will be doing this becasue my bike is currently running an 11:1 piston. Seems the guy that sold it to me was either less than honets, or less than knowledgeable. Once I got the bike apart, I called JE (the supposed brand name of piston IN my bike). The very cool guy (TJ) on the other end informed me that I was actually running a Weisco 11:1 piston. The guys was super cool, and looked all of this up for me. He then found out he had rings for it there, and shipped me a set (very good price too).

So, I wiill be keeping the piston (in good shape, as well as the cylinder) and putting on new rings.

This whole adventure began to repair a leaking head gasket.

I am still going to run some good gas to see if the top end pinging goes away. I suspect bad gas was the bigger culprit.

Now, how do I reset the timing? :)