|New SX Head
|Head removed, new o-rings
It's a good idea to keep the stock head in case you ever want to go back. The higher compression gives a big boost to low-end and mid-range performance and torque. This upgrade won't make the bike into an SX and still maintains smoother more tractable power. To get closer to SX power you must combine the head with a new CDI unit. The kind of riding you do most along with your personal style and preferences will determine what kind of power upgrades you want to do. I like the feel of the SX head along with the red power valve spring and stock XC CDI unit. With this setup I ride most with the ignition mapping wire connected. In this configuration having the wire connected is more aggressive and it revs more free and spins the rear tire more easily. By disconnecting the wire, or flipping a switch in my case, the power will be a bit more mellow and take a little longer to wind up making it a little easier to ride in loose terrain. It seems as though with the stock power valve spring it's more aggressive with the wire disconnected. The SX CDI unit will make it rev more like an SX and tend to make it a little harder to ride on tight trails, but will give it a power boost. It adds horsepower and torque from the bottom to the top and should be combined with the SX head.
|Head comparison, old XC on left, new SX on right. The spark plug sits deeper on the SX because of shallower bowl.
|Another comparison between the two. Notice the shallower bowl on the SX, pictured right.