do NOT thread the rod-connected-to-the-bolt all the way into the pump handle. That is the root of your problem.
This makes your effective rod-connected-to-the-bolt length longer. This has 2 effects.
1) It will make use of the springs inside of the breech to to return the pump stroke out.
2) It will increase the force necessary to pump the marker.
The return spring is secondary. The biggest return force is from the springs inside the breech, which is set by increasing the effective rod length.
Too much rod length may result in extremely hard to pump marker, and possibly bolt not sealing inside breech.
I bought this cci UC kit used so had no idea what was the proper install was. I was so worried about the bolt possibly not sealing inside breech, I have been running my cci undercocking kit with minimum thread showing this entire time!
I just tried one full turn more thread showing, works better than before!
EDIT: I just realized you are the OP and have already applied this.
In that case I would do the following
Take your marker apart, check to make sure you have all the springs in the internals (breech and power tube), apply lube or grease to pieces in contact with the inside of your breech.
Last edited by m1yeh; 10-14-2012 at 03:14 AM.