Crosman 760 reseal issues

Crosman 760 reseal issues

Joined: October 27th, 2006, 12:25 pm

August 30th, 2011, 6:19 pm #1

Taken apart the Crosman 760 (wood forearm, wood stock) and resealed with all new O & Quad rings, cleaned up everthing but still will not take a charge.

1st time had blow by on pump stroke, replaced Quad seal for the second time and polished up mating surface on valve. Worked fine a couple of times but then will exhaust any air on the "backstroke" while pumping. Will take one or two pumps but then will release those on the third through the exhaust port, essentially will not hold any air now.

Advise?
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Joined: March 1st, 2002, 12:22 am

August 30th, 2011, 6:40 pm #2

deformed internally or some dirt in the seat.

dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
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Joined: September 6th, 2006, 3:27 am

August 30th, 2011, 8:40 pm #3

Taken apart the Crosman 760 (wood forearm, wood stock) and resealed with all new O & Quad rings, cleaned up everthing but still will not take a charge.

1st time had blow by on pump stroke, replaced Quad seal for the second time and polished up mating surface on valve. Worked fine a couple of times but then will exhaust any air on the "backstroke" while pumping. Will take one or two pumps but then will release those on the third through the exhaust port, essentially will not hold any air now.

Advise?
check valve upside down ?
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Joined: March 1st, 2002, 12:22 am

August 30th, 2011, 8:47 pm #4

only takes a little gap to dump the air back into the pump tube

dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
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Joined: October 27th, 2006, 12:25 pm

August 31st, 2011, 1:53 am #5

I'll tear it back down and have a look at the check valve.

Thanks.
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Joined: March 1st, 2002, 12:22 am

August 31st, 2011, 3:53 am #6


and make sure the shoulders are square

make sure its round at the tip (reason I say this, is the CV in my 397 had deformed and exhibitied the symtoms you describe)

and check for crud where the CV seats on the valve

 


dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
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Joined: October 27th, 2006, 12:25 pm

September 1st, 2011, 12:07 pm #7

Taken apart the Crosman 760 (wood forearm, wood stock) and resealed with all new O & Quad rings, cleaned up everthing but still will not take a charge.

1st time had blow by on pump stroke, replaced Quad seal for the second time and polished up mating surface on valve. Worked fine a couple of times but then will exhaust any air on the "backstroke" while pumping. Will take one or two pumps but then will release those on the third through the exhaust port, essentially will not hold any air now.

Advise?
Took valve apart again, soaked in cleaner and scrubbed out the insides of the valve. Seems to have been the issue, so far it works fine.

Thanks for the advise.
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