Is the power valve is opening?
When you set the cylinder on the cases, it is easy to mis-align the power valve actuator. If it is not lined up just right, the power valve will not open. If this is the problem, you will have to pull the cylinder off and try again.
BTW, there should be an inspection cap on the left side of the cylinder. If you remove that and start the motor, you should be able to see the shaft at the end of the powervavle rotate 90 degrees when you rev the motor. If it does not rotate, your powervalve is stuck.