Gem Piston Washer Replacement

[Stefran61]

Can anyone give me some guidance on how to replace the piston washer/s on a Gem piston.
Currently looks like two leather washers separated by a thin metal washer with another washer on the end all held in place by I assume a screw with the head ground down.
Many thanks in advance
Steve

[Benelli B76]

Never seen one with a piston washer fitted. They have a thin leather washer at the end of the cylinder to act as a buffer. The steel piston is a good fit to the cylinder to produce pressure. Years ago, like you I thought it needed a piston washer and I made a nice fitting polyurethane one and the power went down.

Baz

[ShakyChef]

I worked on a Diana gem type recently. The piston seal was made from string and grease which was disintegrating and it was not powerful enough to launch a pellet. I replaced it with a 3/4 inch tap washer with a 15mm hole punched in the middle as I had one to hand. It fits well and shoots nicely at 3 ft/lb.

[Stefran61]

Photo added

https://imgur.com/n5eBqyC

[mrto]

Photo added

https://imgur.com/n5eBqyC

I think that is not a piston washer assembly per se,but a sandwiched leather disc intended to be oiled and act as a reservoir of lubricant for the cylinder.

The steel disc acting as the piston crown appears to be riveted on and not the remnants of a squashed screw head.

[Benelli B76]

I think that one of the key indicators is that most Gems have no facility on the end of the piston to fit a washer, no hole with screw thread. My Gem had a centering dimple from the manufacturing process. I tapped it myself to fit a washer which was not needed.


Baz