Use a bit of forked tube smaller than normal (see first few posts in thread) to compress mainspring and remove cylinder pin. Ease pressure and remove guide,mainspring and piston. The piston washer on this was rubber (see end of this post). Clean and lude and replace piston,mainspring and guide. Compress mainspring and refit cylinder pin. Replace barrel and locate the pivot pin and lockscrew and tighten. Replace the cocking slider in the trigger housing and then replace the cocking arm and the 2 pins (one at the breech block and the one that goes through the slot in the trigger housing and joins it to slider). Locate the trigger and replace its 2 pins. Locate the sear and make sure it,s spring is located on it, with the other end hooked on the outside of the trigger housing. Fit the endcap with flange pointing into grips and repalce the grips and the 4 small screws and the larger and smaller one in the pistol grip. Replace sights. This is not a bad plinking pistol although crappily made. You could replace the piston washer with leather or get someone to turn a bit of ptfe or alloy and fit an O ring. The trigger is adjustable via the large screw visable through the underside of the grips but does not do much. It is possible to move it too much so the gun will not cock. At least you can strip this pistol because it has pins instead of Rivetts but I would guess spares are hard to get. Not a bad "Tin can gun" though.