Might want to get an adjustable stroke cam for the machine. I had a lot of chatter at the top of the tube from the needle hitting the side and I adjusted the stroke ( as I have a few with adjustable cams ) and shortened the stroke some and the noise went away.

Also without seeing the machine if the cam is too far forward it will hit the front of the tube and make noise. You can possibly move the cam back or move the motor farther back in the housing.