I recently acquired a 46M, and despite being advertised as 'working great', it's not. Oh well. I'd rather fix it than return it.
It leaks down, and I pulled the air cylinder assembly apart and found lots of flakes and crud on the plunger and down inside the cylinder. There is a coating on the inside of the cylinder that appears to be flaking off, and I'm wondering if anyone else has seen this? I lubed it up and put it back together, a few shots later it's all crudded up again and leaking down. There are scrape marks on the plunger - that doesn't seem right either.
I managed to get a couple of pictures:
izh cylinder coating s.jpg (34.6 KiB) Viewed 998 times
izh cylinder coating 2 s.jpg (43.83 KiB) Viewed 998 times
I took it all apart - whoa that cylinder was tight! Took several upgrades in technique to get the pin and cylinder out. I ended up using an allen key bit from my tool kit - the kind that goes into a driver handle, or screw gun - as a punch, to give a nice surface to hit and a short, stiff column for transferring the energy. A lot of wacks later, it finally let go and started to come out. To get the cylinder to unscrew, I ended up using the heat technique, got the housing hot (not smokin hot, but more than warm) with a propane torch, and then clamped the body of the gun to the table and used a screwdriver through the pivot holes and twisted like heck until it popped loose. I also sprayed some penetrating oil on it between heating sessions. It took some escalation, and there were a few heat cycles while I figured out the best way to clamp it, etc.
It appears to be a chrome plating that is flaking. I picked at the loose bits with the tip of an exacto knife, defining some patches at both ends and along the slots. I then did a very sophisticated hone job on the cylinder (a couple wine corks on a long drill bit, wrapped in 1500 grit sandpaper, not tight but not too loose either, very technical! powered with a cordless drill and kept lubricated under a dribble of water from the faucet). I kept at it until the fragmented edges were smooth. You can still feel them with your nail, but the edges aren't sharp. Like I said, very sophisticated. I also polished the plunger a bit to get rid of the rough scratches where chrome flakes had gotten stuck and scraped it up. Put it back together, took it down to the basement and put about 50 shots through it, all good.
Took it apart again to check, and it all seems OK. Good enough for now - but I'm definitely in the market for a replacement cylinder. The seals aren't in great shape, but I don't want to wreck another set. We'll see how it goes. It seems like it will serve the purpose, which is stress relief at the shop - I got it so I can go put a few pellets through paper every now and then when I can't figure out a design problem. So it isn't going to have a particularly demanding life.