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PostPosted: Wed Feb 13, 2019 10:25 pm 
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Joined: Tue Jan 01, 2019 2:26 pm
Posts: 27
Location: TO, ON.
I ordered a replacement seal kit for my old Powermaster 760 but my Canadian version had a second relief valve attached to keep the fps below 500.
The relief valve also anchors to a brass three way valve body inside the main valve body near midpoint, so my replacement front valve seal is useless for fitment.
These kits that are now standard 3 O-ring, spring, front seal, and rear seal don't come with any parts to reseal the relief valve.
There is a tiny o-ring that is on the base of the relief valve thread so it can seal to the main valve body and it is clearly deformed from time and pressure.
I'd like to know where members are getting o-rings for their guns, or if there are suppliers of o-rings around Toronto?
The local plumbing supplier by me just shrugged. Princess Auto has mega packs of o-rings but no guaranty the smallest in the kit will work.


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PostPosted: Thu Feb 14, 2019 6:24 am 
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Joined: Thu Sep 01, 2005 1:41 pm
Posts: 996
Location: GTA
It's been a long time since I've worked on one of those. I seem to recall one of the 13xx bolt orings fitting, 004, or 006, I think. But my memory is foggy.

Another fix I've used in a pinch is to wrap the part that inserts into the main valve with Teflon tape. Put the T-tape over the old oring.

Third fix, replace the valve.

Getting an oring kit isn't a bad idea. It's handy to have a few sizes on hand. Princess Auto puts them on sale for about $10. Can't beat that.


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PostPosted: Thu Feb 14, 2019 7:24 am 
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Joined: Thu Apr 16, 2015 6:49 pm
Posts: 141
Location: S-E New Brunswick forest
I have found that hydraulic repair shops have an incredible O ring inventory. The have bailed me out many times in the past for all sorts of machinery.


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PostPosted: Thu Feb 14, 2019 11:31 am 
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Joined: Tue Jan 01, 2019 2:26 pm
Posts: 27
Location: TO, ON.
Woody wrote:
It's been a long time since I've worked on one of those. I seem to recall one of the 13xx bolt orings fitting, 004, or 006, I think. But my memory is foggy.

Another fix I've used in a pinch is to wrap the part that inserts into the main valve with Teflon tape. Put the T-tape over the old oring.

Third fix, replace the valve.

Getting an oring kit isn't a bad idea. It's handy to have a few sizes on hand. Princess Auto puts them on sale for about $10. Can't beat that.


I was considering the teflon wrap idea but hoped to find an o-ring.
I'll look into the 13xx o-rings and hydraulic shops first.
Seems hard to find the valve complete, even the body shows unavailable many places.

If I could get a good seal on the connection point and the gun gets good pressure and like new function, I was considering blocking the exit of the relief valve and removing the internals to see if that "free" volume gives me any benefits.


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PostPosted: Sat Feb 16, 2019 12:58 pm 
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Joined: Wed Oct 17, 2007 3:27 am
Posts: 2580
Location: Winnipeg, Canada
I've got one in one of my 7xx something or anothers here, and I soldered the hole closed, after threading out the useless mechanism.
Benefit of this is the volume is a bit of an increase over the current 7xx/13xx line... body on mine is brass, and I used an aluminum insert to keep the 60/40 solder from flowing into the valve.

-D.S.

_________________
"Ain't no half-way"
-S.R.V.


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PostPosted: Wed Feb 20, 2019 1:03 am 
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Joined: Fri Feb 26, 2016 2:42 pm
Posts: 50
does the valve in your 760 look like this: (will attempt to attach photo...)
or does it have a stem at the back which the hammer hits?


Attachments:
late 60's 760 Powermaster valve.png
late 60's 760 Powermaster valve.png [ 701.6 KiB | Viewed 351 times ]
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PostPosted: Fri Feb 22, 2019 11:18 am 
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Joined: Wed Oct 17, 2007 3:27 am
Posts: 2580
Location: Winnipeg, Canada
Looks like someone FTP'd a self-cocker.

Okay from an efficiency stand point almost- with negligible performance gain.
I think scopesandammo still carries a re-seal kit for these.
The extended body mechanical bleed valve vent mentioned by the O.P. only appeared on manual cocking hammer guns.
I had some photo's of one up here previously, but they did not survive the bucket re-org....

-D.S.

_________________
"Ain't no half-way"
-S.R.V.


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PostPosted: Sat Feb 23, 2019 12:56 am 
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Joined: Fri Feb 26, 2016 2:42 pm
Posts: 50
Scarb76,
Shockingly, Canadian Tire had an extensive selection of O-rings. You may find what you need for your 760. ( I found these at the Stockyards in Toronto). Whichever location you go to, look for the drawers full of odd-ball fasteners (nylon nuts & bolts, cotter pins, etc.), there you'll find O-rings. Avoid plumbing section as the same o-rings cost twice as much there. The individually packaged ones were ¢79 each.
But remember, it's Canadian Tire - they may actually have what you need, but it's unlikely any of the fuzzy-faced employees will know what, or where it is. Ha.
(Actually, I think the Paulin ones came from Home Depot but CT has same ones)

(PS-Good eye, Dr. Sharptail! It's from a 760 Powermaster (late 60's - early 70's?) I'm currently trying to fix. I'd never seen a "pop-off" valve before. Couldn't figure out what the hell I was looking at when I first opened it up. It suddenly popped into my head a few hours (beers) later what it was. Hoping the tiny o-ring will replace the flat ring inside the pop-off cap. Will see...)


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image1.jpeg
image1.jpeg [ 649.62 KiB | Viewed 281 times ]
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PostPosted: Tue Mar 12, 2019 3:05 pm 
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Joined: Tue Jan 01, 2019 2:26 pm
Posts: 27
Location: TO, ON.
Sorry. Life got distracted
Then I forgot the post...
Not sure about image posting so it's in two different submissions.
The red arrows are the relief valve (top), where it would attach through the body, and the internal (hat shaped) block it threads into.
The internal block has a passage from front to back for the pumped air to pass through into the main chamber, and also into the threaded portion for the relief valve.
The very bottom components are the replacement kit parts. They are laid out in the position they would sit relative to the originals.
The large new front valve seal is not hollow and would also hit the internal valve channel where "shoulder" of the relief valve block hits. The point on the new seal that would be the stopping point is about .003" before the widest part of the front taper, and the whole OD of the seal is only around .004" wider than the part of chamber it hits. Since there is no way to guide it on center, and it could just keep getting carved with each pressurized misalignment and leave pieces to get jammed on air exit...I'm sticking with the original brass block.
I did get it back together with the original relief valve O-ring and teflon tape plus a couple tiny mods.
1. Drilled out the brass block for a little more air flow (of course the bit broke and the extraction required a bit larger passage). This was in prep for possibly blocking the relief valve exit hole in the future and so allow easier air movement into the main chamber once fired. The passage was larger ahead of the relief valve than it was exiting into the main chamber. Now it's all one diameter.
2. Added a steel BB in place of a small ball bearing in the relief valve. As I mentioned, the old bearing was landing in an off center divot on the valve seal and also seemed like it might have started forcing itself into the spring coils. The BB was a tad larger and I figure once it finds that divot, and the spring can't work around it, the extra diameter should fix any early leakage that might have been in that part of the pressure system.

Thanks for the help. I'll look into CT when I go back in to do any other mods, like seeing if blocking the relief valve exit and removing the internals has a benefit.

Testing just a few pellets, with the cheapo, popular little China made speed tester crony, I've had a range of 400fps with 3 pumps and 7.33gr Exact RS to 599fps at 10 (no bleed off sounds so far).
For fun I tried a few with RWS HyperMax 5.2gr and 705fps ( my note says 8 pumps ) I believe it could have been 10 pumps.
No BBs tested.
Image
https://500px.com/photo/298011735/detail-by-ucimcrazy


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PostPosted: Tue Mar 12, 2019 8:47 pm 
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Joined: Sat Mar 16, 2013 5:15 am
Posts: 3540
Location: Edmonton
Scarb67 wrote:
Sorry. Life got distracted
Then I forgot the post...
Not sure about image posting so it's in two different submissions.
T
he red arrows are the relief valve (top), where it would attach through the body, and the internal (hat shaped) block it threads into.
The internal block has a passage from front to back for the pumped air to pass through into the main chamber, and also into the threaded portion for the relief valve.
The very bottom components are the replacement kit parts. They are laid out in the position they would sit relative to the originals.
The large new front valve seal is not hollow and would also hit the internal valve channel where "shoulder" of the relief valve block hits. The point on the new seal that would be the stopping point is about .003" before the widest part of the front taper, and the whole OD of the seal is only around .004" wider than the part of chamber it hits. Since there is no way to guide it on center, and it could just keep getting carved with each pressurized misalignment and leave pieces to get jammed on air exit...I'm sticking with the original brass block.
I did get it back together with the original relief valve O-ring and teflon tape plus a couple tiny mods.
1. Drilled out the brass block for a little more air flow (of course the bit broke and the extraction required a bit larger passage). This was in prep for possibly blocking the relief valve exit hole in the future and so allow easier air movement into the main chamber once fired. The passage was larger ahead of the relief valve than it was exiting into the main chamber. Now it's all one diameter.
2. Added a steel BB in place of a small ball bearing in the relief valve. As I mentioned, the old bearing was landing in an off center divot on the valve seal and also seemed like it might have started forcing itself into the spring coils. The BB was a tad larger and I figure once it finds that divot, and the spring can't work around it, the extra diameter should fix any early leakage that might have been in that part of the pressure system.

Thanks for the help. I'll look into CT when I go back in to do any other mods, like seeing if blocking the relief valve exit and removing the internals has a benefit.

Testing just a few pellets, with the cheapo, popular little China made speed tester crony, I've had a range of 400fps with 3 pumps and 7.33gr Exact RS to 599fps at 10 (no bleed off sounds so far).
For fun I tried a few with RWS HyperMax 5.2gr and 705fps ( my note says 8 pumps ) I believe it could have been 10 pumps.
No BBs tested.
Image
https://500px.com/photo/298011735/detail-by-ucimcrazy


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