97 cr 250 powervalve

A common mistake is not connecting the actuating rod that runs down the right hand side of the cylinder to the actuator on the bottom end. The rod has a fork that connects to a "nipple" for lack of a better word. That rod causes the pv to open. If you can rotate the actuating rod by hand, its probably not connected. When connected, the two pieces meet at approximately a 90deg angle.

The part I'm referring to as the acutating rod is called the shaft if you click HERE Then go to exhaust valve. See Part #14. You can see the part it connects to on the bottom.

I'd check that first.

Also check for carbon build up in the slot on the center exhaust valve. If its gunked up it wont let the valve travel properly to open and close or may let it only move partially.

Could be worn out, broke, even non-existant. If you're sure its hooked correctly up its time to dig a little further.