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FT Piston Valve Fail.....

August 7 2012 at 9:34 AM

WyoMan  (Login WyoMan)
Crosman Forum Member
from IP address 66.29.182.22

.....I just installed a FT kit in a 1322 and the valve will only take one or two pumps and then the pump stroke air leaks out the front grip frame screw hole. This is just the type of weirdness that happens to me. If I tighten the screw it helps a little. If I loosen the screw the valve won't take any air.

Do I have a valve body o-ring leak? I deburred pump tube w/ 400 grit and oiled o-ring with 30wt ND prior to install. Are there any tricks to the trade here?

Thanks



WyoMan
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(Login airgunandy)
Crosman Forum Member
206.208.93.60

Re: FT Piston Valve Fail.....

August 7 2012, 10:37 AM 

Sounds like a valve body O-ring leak to me. Maybe FT kit had wrong size O-ring?

Is the valve your original valve? If not, it may be the valve was made wrong and the screw hole was drilled too deep into the inside of the valve. But that's a long shot.

I plink, therefore I am.

 
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WyoMan
(Login WyoMan)
Crosman Forum Member
66.29.182.22

Re: FT Piston Valve Fail

August 7 2012, 10:56 AM 

The valve is not original. It was purchased it a kit. The piston seals OK using same size o-ring, but then again, I can't accumulate enough pressure right now to be 100% sure.

Funny you mentioned the screw hole - I was thinking the same thing because I was so sure and careful with the valve install. But here's another funny thing. With the screw completely removed, the piston will suck air into the airtube thru the screw hole on the intake stroke. I'm thinking now it's got to be the o-ring, but I don't know why (if you don't know why it could happen again, to me anyway).

I know I'm gonna have to tear her down again, was dreading this.

Wanted to know if there is a fail safe procedure to avoid this leak

Thanks,

 



WyoMan
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dan house
(Login dan_house)
Crosman Forum Member
153.90.162.47

Couple of things

August 7 2012, 11:06 AM 

During my AC397 buiild , I had every thing go wring, except having it exit out the pump tube under pressure.

you seem to be convinced that the or is holding, so lets rule that aout. Do you cock it before starting to pump? Make sure the check valve isnt "sticking" open after a very few stroke. And add a wrap or two of teflon plumbers tape to the screw/bolt that holds the grip frame and valve together. If that works, then either the bolt threads have been worn or the hole in the valve is worn and getting big enough to allow some air to pass, especially under pressure. 



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WyoMan
(Login WyoMan)
Crosman Forum Member
66.29.182.22

The Valve will hold pressure......

August 7 2012, 11:21 AM 

......what little you can get in there. If you pump real fast you can even add some more air (it will take the first one or two pumps ok).

I was thinking about teflon on that screw since tightening it seems to help a little, but how can the air even get there unless o-ring is wacked?

Good point about cocking first (I generally do it last) since modded valves may have lighter spring but if it takes one or two OK then exhaust should be locked up

Thanks,



WyoMan
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(Login rsterne)
Crosman Forum Member
66.244.241.34

From this statement, it sounds to me....

August 7 2012, 11:49 AM 

like the screw hole is drilled too deep....

"With the screw completely removed, the piston will suck air into the airtube thru the screw hole on the intake stroke."

Bob

 
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WyoMan
(Login WyoMan)
Crosman Forum Member
66.29.182.22

Thanks Guys :-) nt

August 7 2012, 12:10 PM 


 
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