Smith and Wesson 79g / Daisy Powerline 790 power issues

[evert]

Having struggled with a few of these over the years, I've come across some of them that have had power issues.
It seems like the valves dont open correctly on some of the guns, and the problem seems to be valve related and not related to the striker, as the problem follows the vale when I switch valves between guns.

The only explanation that seems reasonable to me is that the valve seal has taken a set over time, and that this causes them to stick hard when the striker hits the valve stem

Has anyone on here had any experience with this, or have any ideas on how to fix the problem?

[Mark D]

Assuming all other things ( hammer & valve spring etc) being equal between pistols, just fit a new exhaust valve seal. In my experience the old seals leak and then break up.

https://flic.kr/p/2qgvRJD

[evert]

Assuming all other things ( hammer & valve spring etc) being equal between pistols, just fit a new exhaust valve seal. In my experience the old seals leak and then break up.

https://flic.kr/p/2qgvRJD

Thanks, that's exactly what I'm suspecting. I have tried changing valves between pistols, and the problems have followed the valves.
Where duo you get the seals?

[Mark D]

Thanks, that's exactly what I'm suspecting. I have tried changing valves between pistols, and the problems have followed the valves.
Where duo you get the seals?

Stick a wanted post in the 'Collectable airguns' section - there are a couple of guys who can do this, you would need to send them your exhaust valve as the stem needs pressing out of the body to do it properly.

[evert]

Stick a wanted post in the 'Collectable airguns' section - there are a couple of guys who can do this, you would need to send them your exhaust valve as the stem needs pressing out of the body to do it properly.

Thanks. Living in Norway makes sending parts off for service a bit expensive.
I may have a go myself, just need to look for a suitable seal material.

These link show the process:
https://anotherairgunblog.blogspot.c...sembly_04.html
https://anotherairgunblog.blogspot.c...model-79g.html

I found a place that sells resealing kits with a complete replacement valve poppet/stem:
https://www.bakerairguns.com/product...79g-seal-kits/

The kit seems to have a valve poppet head made completely of some kind of plastic, like what is used in many PCPs.
Making something like this could also be worth a try.