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Air Gun Home Forum Index » Airgun Smithing » Crosman Exhaust valve repair
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Crosman Exhaust valve repair 
PostPosted: Sun Feb 15, 2015 8:17 pm Reply with quote
lampy
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Location: South Dakota
I have a couple bad crosman exhaust valves in my parts stash and have thought about trying to repair them. I like the older valves with their brass body, not sure if it really matters but I feel better having the extra metal in the valve. This is the way I came up with....

This exhaust valve came out of a Crosman 766 project rifle. The valve was pretty corroded and the sealing surface on the exhaust valve was shot.


The stem of the valve is a press fit in the brass body. With the stem of the valve held in my bench vice, I applied heat to the brass body with a small butane torch. I used my pliers to pry the body of the valve free from the stem. Some care is needed to not damage the brass body or the stem.


With the valve apart and the crud cleaned up, I got the measurements I needed to make a new seal. I used some HDPE (High Density Polyethelene) rod I had. I used the HDPE because it is a bit softer than Delrin. Turned on the lathe and parted off I had my new seal.


The new seal installed in the body.


The stem pressed back in and I have a rebuilt valve. This being my first attempt I expected it to not work but to my surprise once it was reassembled the 766 pumped up and held air Shocked I have some Delrin and PTFE rods I was going to try but since the HDPE worked I may just stick with it for future rebuilds.

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PostPosted: Sun Feb 15, 2015 9:45 pm Reply with quote
Slavia
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Location: Waseca, Minnesota, USA
It's nice to have an alternative in the repertoire when you don't want to wait for parts to be shipped.

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PostPosted: Sun Feb 15, 2015 10:06 pm Reply with quote
lampy
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Location: South Dakota
This exhaust valve has a shorter stem than the good spare I had in my parts stash and my spare doesn't have the brass body. I could have used the Dremel to cut the spare to the correct length but I wanted to see if I could repair the original. Also since this valve is going in my 766 project, if everything works out I'm going to try it on HPA and it will be pumped up to 2000 psi. I will feel better about the HPA tests if the exhaust valve has the brass supporting the seal.
The later model Crosman exhaust valves I've seen don't have the brass body, so I wanted to see if I could save this older valve.

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Crosman Exhaust valve repair 
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