This is a new to me 9500, and the variable speed for the header will not stay constant.  Most of the time it will creep up in speed and stay there, and once in a while it will drop from 540 down to 320 for a couple of seconds and return.  I am not going very fast and the head seem to be feeding at an even pace.  This was late last night so I have not been able to check  the tension on the belt or the sheaves.  Thanks for your help.

Sam