I assume you are using a 4 MHz crystal where the PULSOUT unit time would be 10 uS per count giving 1500 uS for a centred servo.

Your code will loop extremely fast - way too fast for a servo thst is looking for a refresh rate around 50 per second.

Try putting
PAUSE 18
in youf FOR/NEXT I loop and it should centre the servo.

HTH
Brian