Question
my orbit valve will not open fully it flutters.
once in a while it will open fully.
is my pressure to high or to low.

Answer
It may not be a pressure problem.  First make sure that the supply valve for the sprinklers is all the way open.  Then adjust the flow control on the valve to about halfway open or a little more.  If this doesnt help, you need to dissemble the valve and check the internal parts for wear, tears or damage.  It could also be an obstruction in the valve, so clean out any debris you find inside.  The link below will help you service the valve.  

http://www.irrigationtutorials.com/faq/repair-valve.htm