I recently purchased a used Kuhn CF-50 air hammer. It was not running and had no dies at the time. Upon setting it up in my shop and installing the dies, the hammer hits fine but stays at the lower end of the stroke fluttering up and down when I back off on the treadle. The owner's manual lists only 2 valves to adjust . I have loosened and tightened the regulating valve with no effect on this problem. The directions on the setting of the control valve do not match the accompaning illustration. My valve is set to the written directions, and I am hesitant to change it as it is physically impossible to completely match the illustration. There are 2 blocks locking onto 2 shafts that are connected by a rod. The directions call for one to be parrallel to the body and the other indexes to a mark on it's shaft. Setting it this way causes the second block to be about 20 degrees out of parrallel yet the picture shows them both parrallel. I would sure appreciate advice from anyone familiar with this machine.
Thanks, John Barron
530-333-1129

John: I think it is irreparable. I'll come down from Eugene and take it off of your hands. I only have your health in mind. Eric Sprado

Is your belt tight and free of grease and oil?

Is the ram seal blowing ? are there any split hoses inside the machine ? Is it running at the correct speed?

Mine is a KO (27kb) so I doubt that my factory manual materials would be of much use. Centaur Forge was the US distributor for Kuhn back when I bought mine in the early 90's. I would try calling them and see if someone might be able to help or refer you to another owner of a CF-50.

One thing that I would caution you about Kuhn hammers is that the piston wrist pin has very tight tollerances making it uncertain if adequate grease is getting to the the pin bearing surfaces. I finally bought a pneumatic grease gun to solve trhis problem.

a few options from easy down:
foot pedal to valve linkage warlered/loose
spring return on pedal linkage weak
or something preventing pedal/linkage from wanting to go all the way home (it does not take much in linkage to do this, think leaky faucet and you need zero air passage when pedal up.

worn rear cylinder rings, these wear much faster due to they make complete cycles all the time the hammer is on.
worn front lower ring, but this usually is accompanied with oil and air blowing scale in your face.

factory valve settings are zero point, they are touchy too.

This is an old post but hey John, what did you come up with??  I have the same hammer and its doing this exact same thing.  Air hoses are fine and all valves are where they are suppose to be.  Georg Kuhn has tried to help but not sure if the language is a barrier