Umarex Notos leaking air

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Pantanni

Pantanni

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Aug 12, 2024
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St. Louis, MO, USA
About 2 weeks ago my Notos stopped working in the middle of a shot string. I disassembled it and found a broken poppet valve originally.

It's taking a long time for my poppet from Maple Custom Products to arrive, so I decided to disassemble the gun again and think i see an unseated o-ring for part #40 "exhaust valve" when looking through the hole in the bottom of the breech.

I've included a picture of the suspected unseated o-ring and wondered if I can push the exhaust valve out to replace and/or reseat the original o-ring if it has no damage (unlikely)? I've tried pushing it out from the side opposite where the poppet seats but didn't have any luck yet. I wanted to see if it's possible to do before I go too far and break something else.

Thanks in advance.

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I've reseated the exhaust valve with the original o-rings hoping that might do something but it is still leaking air out of the barrel. I suppose I'll need to wait for the poppet to arrive to see if that fixes the problem. However in the meantime I'd like to order new o-rings for the exhaust valve. The diagram lists them as 9x1.5 and 6x1.5, I will order some but there are different materials with different hardnesses. Does anyone know what material and hardness i should look for?
 
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Please PM me your order# and I can check the status for you. It's taking a bit longer than usual for shipping due to the postal strike and the holidays but shouldn't take more than 2 weeks to get to you.

Now back to your original question, the orings are FKM but Nitrile orings will also work. Just make sure you add a dab of silicone grease when pushing back the valve body.

If air is leaking from the barrel then it's 99.99% cracked poppet valve.
 
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mcp said:
Please PM me your order# and I can check the status for you. It's taking a bit longer than usual for shipping due to the postal strike and the holidays but shouldn't take more than 2 weeks to get to you.

Now back to your original question, the orings are FKM but Nitrile orings will also work. Just make sure you add a dab of silicone grease when pushing back the valve body.

If air is leaking from the barrel then it's 99.99% cracked poppet valve.
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Thank you for responding. I read about the strike on USPS's website and do not blame MCP. The poppet arrived yesterday and after I installed it into the Notos, it is back to working order without new o-rings. I did order some spares from Captain O-ring and will have them available in the future.

Thank you for making these poppets as trying to source one from Umarex was not working well. They didn't have them immediately available and told me to keep checking back week to week...
 
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Pantanni said:
Thank you for responding. I read about the strike on USPS's website and do not blame MCP. The poppet arrived yesterday and after I installed it into the Notos, it is back to working order without new o-rings. I did order some spares from Captain O-ring and will have them available in the future.

Thank you for making these poppets as trying to source one from Umarex was not working well. They didn't have them immediately available and told me to keep checking back week to week...
Click to expand...
Did you get an OEM or aftermarket?
 
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i need to replace that same o-ring. i’m suspecting mine to be damaged from when i took part #40 out. i feel a slight puff of air on the side of my cheek with every shot. still able to push 15.9gr at 850fps though. i wonder if i’ll gain anymore fps. i’m also suspecting that it could also be the cause of my deviation being very stable.
 
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daddypaddy said:
i need to replace that same o-ring. i’m suspecting mine to be damaged from when i took part #40 out. i feel a slight puff of air on the side of my cheek with every shot. still able to push 15.9gr at 850fps though. i wonder if i’ll gain anymore fps. i’m also suspecting that it could also be the cause of my deviation being very stable.
Click to expand...
I'm getting 852 with 17gr slugs. 830s with 18.13s. I'm gonna order the 500mm barrel. I'm positive I can have 18s at 870s and the slugs near 900. Running at 2200psi I noticed there was no change on the entire hammer spring range. Very little change. I weighted the hammer a little and got some more oomph... The 18s went from 761 to 795. . then I got the bright idea to put one of those delrin gaskets that you'd usually put in the pressure gauge outlets into the pocket of the hammer adding tension. Saw 900 for the first time with that on a 15.9. if you're trying to get some serious energy. Try that simple trick. Try running 2150-2400 on the reg.
 
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$p00kygH0ST said:
I'm getting 852 with 17gr slugs. 830s with 18.13s. I'm gonna order the 500mm barrel. I'm positive I can have 18s at 870s and the slugs near 900. Running at 2200psi I noticed there was no change on the entire hammer spring range. Very little change. I weighted the hammer a little and got some more oomph... The 18s went from 761 to 795. . then I got the bright idea to put one of those delrin gaskets that you'd usually put in the pressure gauge outlets into the pocket of the hammer adding tension. Saw 900 for the first time with that on a 15.9. if you're trying to get some series energy. Try that simple trick. Try running 2150-2400 on the reg.
Click to expand...
I had the same experience with the hammer spring, I'm glad to hear it's a similar experience across the board. How did you add weight to the hammer?

I'm guessing you bored the air transfer ports? I heard from firewalker to bore to 4.5mm. Ive yet to bore them out but plan to tonight. With the dream valve and the stock air transfer ports I didn't get any improvement in FPS, maybe a slight decrease.
 
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Pantanni said:
I had the same experience with the hammer spring, I'm glad to hear it's a similar experience across the board. How did you add weight to the hammer?

I'm guessing you bored the air transfer ports? I heard from firewalker to bore to 4.5mm. Ive yet to bore them out but plan to tonight. With the dream valve and the stock air transfer ports I didn't get any improvement in FPS, maybe a slight decrease.
Click to expand...
Yeah. With the block and reg I added a plenum, all bored to 4.5 and I chamfered the tp hole.in the breech, and the inside of the valve exhaust. First I bored into the original hammer and added lead where material was removed. Had a friend with access to a lathe turn a tungsten hammer. Should've just added the damn delrin washer from the jump. With the added tension.. the heavy hammer did way too much. Went from 22-25 shots per tube fill to off reg at 10 shots of 12rd mag. My 500cc bottle went from damn near 150 shots from 250-160 to 60. Got a replacement hammer off of eBay luckily. Now I'm getting about 105 shots per fill.

Edit.

I'm running at 2250-2325 on the reg best as I can tell. Not a very exact precise gauge.
But at that pressure, starting with the HS screw all the way backed out past flush. Every tiny HS adjustment shows. At minimum HS 18.13s will be 755-770

I am just inside of 1.5mm In past flush and they're at 832.. im sure if I boosted up to 2400-2600 I could reach goal power. But I'm not trying to shrink the shot count anymore. I'm sure adding another 5" of barrel will do more than another 150-175 psi
 
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$p00kygH0ST said:
I'm getting 852 with 17gr slugs. 830s with 18.13s. I'm gonna order the 500mm barrel. I'm positive I can have 18s at 870s and the slugs near 900. Running at 2200psi I noticed there was no change on the entire hammer spring range. Very little change. I weighted the hammer a little and got some more oomph... The 18s went from 761 to 795. . then I got the bright idea to put one of those delrin gaskets that you'd usually put in the pressure gauge outlets into the pocket of the hammer adding tension. Saw 900 for the first time with that on a 15.9. if you're trying to get some serious energy. Try that simple trick. Try running 2150-2400 on the reg.
Click to expand...
i cut a half coil off the spring when i first got the gun and took some weight off the hammer. currently my reg is set at 2000-2100. hst wise, i have the tensioning screw flush with the block only so i can bring my fps down to around 590fps if i ever needed to. i did remove some metal from the little duck tail behind the hts so i can back it out about 80% the length of the hts itself.
 
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Pantanni said:
I had the same experience with the hammer spring, I'm glad to hear it's a similar experience across the board. How did you add weight to the hammer?

I'm guessing you bored the air transfer ports? I heard from firewalker to bore to 4.5mm. Ive yet to bore them out but plan to tonight. With the dream valve and the stock air transfer ports I didn't get any improvement in FPS, maybe a slight decrease.
Click to expand...

The 4.5mm porting is as far as you can port them all without having to re-tap the TP plug hole and you would have to elongate the barrel port so that the pellets would not drop into the barrel port.

De-burring and smoothing the air path is important as is making sure to not cut/chip o-rings when reassembling the gun.
 
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Firewalker said:
The 4.5mm porting is as far as you can port them all without having to re-tap the TP plug hole
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I think this is where I'm currently having problems. I have a 4.5mm drill bit and a 4.5mm reamer but they both hit the threads in that hole.

Are you talking about this hole?

I've removed the oring, and disassembled everything, not like in this picture, before I attempted to see how the 4.5mm drill bit non threaded shank end would slide and it hits the threads. It doesn't slide clear to the hole I need to enlarge.

20241209_152011.jpg
 
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Pantanni said:
I think this is where I'm currently having problems. I have a 4.5mm drill bit and a 4.5mm reamer but they both hit the threads in that hole.

Are you talking about this hole?

I've removed the oring, and disassembled everything, not like in this picture, before I attempted to see how the 4.5mm drill bit non threaded shank end would slide and it hits the threads. It doesn't slide clear to the hole I need to enlarge.

View attachment 520595
Click to expand...
Same thing happened with me. So I drilled to 4.3 and did some very careful work with a fine abrasive cone bit. Then polished
 
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Pantanni said:
Do you remember how thick of a washer you used? Did your get it from a hardware store?
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Quite literally one of the white delrin washers from the socket of a 1/8npt threaded air gauge hole. In fact, it was one of the spares from my huben reg kit I'm pretty sure it's 3 or 3.5mm thick maybe 8mm wide
 
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