Is this an S series governor? When set up properly, the return spring should be applying resistance to ANY movement of the governor arm off the fine pitch RPM stop. I believe it is set up this way so that any breakage of the cable or components will put the prop in fine pitch, as well as to account for slop in the cable assembly and maintain a precise RPM. It is likely that someone took the arm off and allowed the piece below it (the circular steel piece with the arm that catches the return spring) to come off and didn't not re-install it properly. There is a special procedure to get it back on properly and with the correct spring tension.
Do you have the hartzell maintenance manual? It has the procedure for installing that piece that catches the spring. It is not hard to accomplish. It is not in the owners manual, as they don't expect folks to remove that part. Normally the arm can come off without removing the piece below it if care is taken.
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Last edited by lr172 : 04-17-2021 at 08:58 AM.