'76 Pumpmaster 760 can't remove air cylinder

[Cityevader]

I don't want to damage it, but it won't budge.
Do i focus on pressing/whacking the small nipple end? Or on the larger diameter portion along the I.D. of the air tube?

 

[teerex.otw]

How far have you disassembled it so far ?
If you’ve removed the receiver side cover (l.h.) and the barrel, the only things that can keep the valve from being removed toward the muzzle are the o-ring, or possibly some damage to the tube…There is a screw that goes through the side cover and the tube to hold the valve in place, and also a small metal cup under the barrel seal that aligns with a slot in the transfer port sleeve. If both have been removed and it’s still stuck, you night try some Kroil (or similar). Whatever you do, DO NOT damage the nipple on the front of the valve.

 

[Cityevader]

The disassembly level is, air tube is completely separated from the rest.
Thisisn't quite a restoration, but still a full shake down, clean out, and reseal of a new to me freebie.

 

[teerex.otw]

It sounds like the o-ring is stuck, or maybe a burr, etc.
If it doesn’t come loose with penetrating oil, I would suggest contacting this fellow (a Crosman guru…This is where I get my Crosman stuff).

 

[Cityevader]

With penetrating oil and much pounding, it came out after mushrooming one end of it (in pic, left end.)....unless that mushroomed piece wadn't supposed to come out!
Silly thing is, by the time I'm done i could have purchased an entirely new gun.

 

[teerex.otw]

Well…yes, I guess.
The newer ones shoot ok, but they kinda’ feel like they’re made of styrofoam. These old brass-bolt, alloy frame, self-cockers are a classic (and the supply is dwindling)
imho, well worth the effort & $ to fix.
On yours; judging by the scratch from the bolt hole on the pointed end, looks like there may be a burr or something around the bolt hole in the pump tube. Also, the brass end cap that goes in the peened-over steel part (sleeve) has to slide easily (this is critical to the function of the gun), if it doesn’t, the steel sleeve may need to be replaced.

Note: I’m just trying to be helpful, apologies if you already know this stuff…One thing I’ve learned from these forums is that you never really know the extent of someone else’s
experience. So just in case…

Best of luck,
Rex

 

[Cityevader]

I'm ignorant...isn't this valve pre-1975?
Maybe i mis-read the serial #?

 

[Cityevader]

On yours; judging by the scratch from the bolt hole on the pointed end, looks like there may be a burr or something around the bolt hole in the pump tube.

Indeed, there is brass peeking from the hole still... it's on the to-do list.

 

[teerex.otw]

All I have to go on is exploded views on JG’s site.
Up until June ‘75 they used a flat-ended valve. Starting July ‘75 thru June ‘77 they used your style with the cone-shaped end and changed the plunger style.
Starting July ‘77 looks like they eliminated the self-cocking (auto-reset) feature and changed a bunch of stuff to go with it.
Yours might be earlier than the ‘75-‘77 if it was repaired/upgraded along the way (although it’s gonna’ take more knowledge than I have to tell if that’s even possible).

 

[Big Bore 44]

B76 is Feb 76. That's the right valve.

 

[Cityevader]

Thank you.
I wish info wasn't scattered all over the internet, instead of a single source.
Videos and pics of people "saying" their's is such and such production year adds to confusion when it is incorrect.

 

[teerex.otw]

This is so true of a lot of things.
You might want to Google “Crosman product dates of manufacture”
According to Crosman, yours would be the 4th variant, built between July ‘75 (when they first started using date codes) and ‘77.
Mine is a 3rd variant, and has nothing but a description and s/n.
Starting with the 5th var. they started using the plastic bolt and manual-cocking.

Wish History was this interesting when I was in school…might’ve gotten better grades !

 

[Cityevader]

Curses...i saw the cylinder AND cup-thingy on ebay, but after confirming my cylinder was correct, when i went back the next day to nab it...gone!
It looks like the cup-thingy seals against the rear plug-thingy so replacement is necessary.
Sigh...now i wait.