Crosman 102

Crosman 102

Joined: October 30th, 2010, 12:59 am

February 12th, 2012, 9:27 pm #1

Have a problem that someone can maybe can help with, after a few pumps pressure is applied to pump arm forcing it down. Will pump to 8 pumps and dump all air but pump arm has to held up. All seals are fine and rifle holds pressure, check valve and spring appear ok and pump arm spring has been replaced.
Steve
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Joined: July 22nd, 2011, 4:46 am

February 12th, 2012, 10:05 pm #2

If I'm reading you right, the problem is that the pump handle doesn't stay in place but instead falls down.

The answer to this is to "Over Toggle" the pump linkage. This is where the length of the pump linkage is actually longer than needed to meet the back of the compression chamber. This bit of extra lenght (the Over Toggle) places tension on the pump linkage. This tension is what holds the pump handle up.

The "Over Toggle" term comes from Crosman engineering.
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Joined: May 20th, 2005, 1:44 am

February 12th, 2012, 10:46 pm #3

Have a problem that someone can maybe can help with, after a few pumps pressure is applied to pump arm forcing it down. Will pump to 8 pumps and dump all air but pump arm has to held up. All seals are fine and rifle holds pressure, check valve and spring appear ok and pump arm spring has been replaced.
Steve
"after a few pumps pressure is applied to pump arm forcing it down."

Pressure from where? What is forcing it down? If there is pressure being applied to the arm and its dropping on it own, it seems to me that the check valve maybe be leaking. Pump it a few times, then turn it upside down with the pump arm about 3/4 closed. If the arm opens on its own the chack valve is bad. Air pressure is slowly escaping from the valve and pushing the rod back, opening the arm.
If the check valve is ok, adjust the linkage so that the pump head makes contact with the valve face when the handle is about 1 inch from closing and you need to snap it closed a bit.

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Joined: July 22nd, 2011, 4:46 am

February 13th, 2012, 2:08 am #4

I agree that it is most likely that the check valve is leaking.
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Joined: October 30th, 2010, 12:59 am

February 13th, 2012, 4:19 am #5

Thanks for the input, the check valve probably is the problem, the pressure against the pump arm increases slightly with each pump. Although the gun will hold air for months if left.
Steve
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Joined: May 13th, 2005, 8:02 pm

February 13th, 2012, 4:30 am #6

Alan at ABairgun told me the same thing Dave has recommended and it worked like a charm.






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Joined: July 22nd, 2011, 4:46 am

February 13th, 2012, 7:52 am #7

If the pump stroke is set long enough to over toggle, then even if a check valve is leaking a bit, the pump arm will stay up.

With time and use, the length of the pump rod always will need a little tweaking.
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Joined: October 30th, 2010, 12:59 am

February 14th, 2012, 8:29 am #8

Certain check valve isnt leaking, resealed valve and refaced valve seat. adjusted pump cup as far forward as possible. Pump arm tends to drop away without air, and more so as a few pumps are applied, although it takes little hand pressure to hold it in place, hits hard though, has accounted for a couple of rabbits lately
Steve
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Joined: July 22nd, 2011, 4:46 am

February 14th, 2012, 7:39 pm #9

The pump rod has a pretty good amount of adjustment available. To be clear, the pump rod adjustment is done on the end where the pump rod screws into the plunger guide https://www.facebook.com/photo.php?fbid ... =3&theater)

Loosen the nut on the pump rod and then rotate the pump rod counter clockwise to lengthen the pump assembly. Get the pump to the point where the pump just bottoms out on the valve chamber. Then, set over toggle: by loosen nut again and rotate the pump rod about 1/4 turn additional counter clockwise.

If there really is no adjustment left, then there has been a tremendous amount of wear in the pump linkages. I would inspect the entire pump assembly for excess wear.

Note: I would never assume that a check valve is working properly, just because it has been recently serviced. Things can go wrong very fast. A loose bit of metal can get stuck on the valve face. etc.

From your description, it sounds like the pump arm is being pushed down by air pressure not just falling down. That's indication of a leaky check valve.

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Joined: October 30th, 2010, 12:59 am

February 16th, 2012, 8:22 am #10

Problem solved, the pump arm on this rifle was rubber, which probably wasnt the original, by sanding away an amount and allowing the the arm to close up further around the compression tube, it works. Pump arm snaps into place and holds when fully pumped. Thanks again for help
Steve
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