I've had this gun about 20 years, bought it used at a gun show, been plinking with it off and on ever since. It started being velocity inconsistent lately, sometimes no resistance on the closing stroke, so I got the kit from Daisy to rebuild the pump and valve. Process was pretty simple. Innerds quite nasty, but cleaned up pretty easily. Did not touch the trigger/hammer parts on this go around. Still having the same problem. I did notice if I leave the pump handle full open for a full second or two, rather than closing it immediately, I get a fuller charge. I just read about cocking the hammer BEFORE charging the air, something I have NEVER done before, so I will try that tomorrow and see if it makes any difference. I'm not expecting that to help, since I don't hear air escaping, it just seems like the air isn't filling the pump tube when the handle is open like it should...I noticed the silver pump tube shifts slightly between handle moving towards open and then back towards closed -- maybe a 1/16" -- maybe enough for the o-ring to not clear the gap at full open, thus not letting air in...? Will investigate tomorrow. What is supposed to hold the pump tube from shifting forward when opening the handle? While cleaning the compression chamber, I found a ring of what I think is cardboard along its outer perimeter. Previous owner making it smaller to increase pressure/velocity??? Does this hack work?On reassembly I did not have the small spacer that fits between the barrel and...receiver? ... Nothing fell off during disassembly so guessing it's been gone a long time. I may just make one instead of ordering -- can anyone tell me the thickness at the vertical centerline of it, i.e. at its thinnest part? Thanks for any thoughts on what's going on with this thing, and fixing it up for another 20+ years of service!
TMhmmm, it sounds like the piston is not being pulled back far enough.In looking at the Daisy repair slides that I have, it looks like the piston is NOT adjustable, like the old ones were.In looking at the repair slides, I have a thought:1 - The air tube is sealed onto the receiver with an O-ring. 2 - Based on what I see, the air tube "should not" be moving forward, as you say yours is.3 - The air tube has a U shaped cutout that faces the charging handle. That would be the air intake for the piston. 4 - The seal of the piston has to clear the cutout for the air to get in, so that you can charge the gun.5 - Your description sure sounds like the piston seal is not clearing the cutout.6 - When I look at my 853, when I lift the charging handle and look at the cutout, the O-ring on the piston "just" clears the cutout.7 - If the tube is moving forward 1/16", that movement could be preventing the piston from reaching the cutout in the tube. As I said, the O-ring "just clears" the cutout, and maybe not even by 1/16."8 - There is a black painted metal "frame" that slides over the air tube, and clips onto the receiver. 9 - The picture shows that the frame has a step in it. I think that step may holding the air tube onto the receiver.10 - Check the ears that clip onto the receiver. If those don't clip on properly, the frame would not be holding the tube onto the receiver.
Chalk it up as "problem solved", mystery remains, lol. Hmmm, I think I used red ATF once, thinking it was the same as pell gun oil, maybe I caused this. I have since learned that pell gun oil is Lubrication Engineers 30wt, not ATF. Possibly something in the ATF caused the piston to swell... I probably should order new parts as a penance for my sins, lol.Thanks for your input! Hopefully it's smooth shooting from here on...