Canadian Airgun Forum

While shooting my B-510 the gun just decided that it would no longer hold the air when pumped. All the air seems to be leaking out of the barrel because I can hear it escaping when pumped. I did some research online and I found out that someone else had the same issue and the problem was with the exhaust valve not sealing. I've only taken apart 2 air guns before, both being spring pistons so I'm too familiar with the mechanism at hand. If anyone could help me out here with how to fix this that would be great, thanks

Sorry messed up on the name its a B5-10 here's a pic

You COULD.....sell it to me.

Al

That a common problem with the B5-10. I used to have one and it kept happening until I replaced it with a delrin seal custom made by an inactive member here. The seal that fails looks like a flat o-ring. You should always cock the hammer first before pumping to prevent this from happening to the low quality original seals.

I wish I still had the gun to take pics, but from memory, I believe you remove the grip handle/bottom receiver section by unscrewing the screws, then do the same for the aluminum upper receiver part. The cocking knob also unscrews out by by turning to counter clockwise. The valve parts should be in the upper receiver. The gun should have came with a valve nut opening tool (a flat blued piece of metal). It has 2 teeth on the outside edge that will fit the brass valve cover nut. Turn counter clockwise and all the parts of the valve should come out easily. Usually, there is nothing wrong with the air intake seal (closer to the front part of the gun). It's the stem seal that seals the valve from the barrel that's the issue.

While you have the gun open, might as well de-burr the sear component too (only smooth out rough spots, try not to remove enough material to change the geometry). This makes a huge difference in trigger pull and accuracy. Here's a related post from another forum with nice pictures:

http://www.network54.com/Forum/113813/t ... 0+pictures

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"...await the right moment for one, and only one well-aimed shot" - Vassili Zaitsev

The delrin stem sounds like a good option if you can find someone to make you one. Heck get me a few while you're at it.
There is a way to modify a Crosman 13xx valve stem to work in the B5-10. I did it to one of mine long ago, can't remember the details exactly. I remember shortening the stem and maybe boring out the hole for it in the valve body then chamfering the lip to make a good seal. I also remember the posibility of screwing it up and making the gun useless was there.
I think I have a PDF on the mod, I'll see if I can dig it up.

like triggerhappy416 said its a flat washer type seal...pretty simple fix
I'd be interested in seeing that PDF as well woody...thanks

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"A candle loses nothing by lighting another candle"

any diagrams on this gun? I'm still a bit unsure on what part it is and it would clarify things if I knew what I was looking at

not much out there on the net...found this it has a couple pics, the pic is an already modified delrin stem seal, if I had time I would dissemble mine and post some new pics, maybe someday....
http://www.network54.com/Forum/113813/t ... +Questions

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"A candle loses nothing by lighting another candle"

Ask and Ye shall receive.
I found this online years ago, it is not mine. I have done it to one gun successfully.
One thing with the B5 is don't over pump it unless you upgrade the seals. I think it was 8 pumps max. These things can build some serious pressure.
Another cool mod I did was have a flat top piston made to use an oring as the piston seal. I figured since seals aren't available this will keep the gun shooting long after the seals go. Piston is very similar to the front half of a 13xx, I can't remember the thread size though.
If someone wants to make up some delrin seals for the B5 I would buy a few.

much appreciated... thanks

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"A candle loses nothing by lighting another candle"