ATI NOVA LIBERTY LEAKY POPPET and VALVE connection

[MichaelScholtz]

OK guys, I did the balloon test on the end of the rifle and my poppet is leaking. How do you get the valve out? I've got the poppet out and the set screw that holds the valve in I think but it will not come out.

Take the hammer and trigger assembly off. With the set screw on the bottom off, tap the back of the valve with a wooden dowel. Tap tap tap but don't smack it.

I went ahead and eliminate the problem all together by having 2mm stem and counter sunk valve face and new poppet.

That's a nice mod, I think I could manage that. I would be worried however that the hammer force may shear it on the brim.

[MichaelScholtz]

Most are saying that Delrin is the best material, but would teflon not also be a good option for this. repair or as above modification ?

[mikeyb]

Most are saying that Delrin is the best material, but would teflon not also be a good option for this. repair or as above modification ?

Teflon can and will cold flow under high pressure impact. I thought it would be a good material for a seal on a beer bottling line, but it did not do well under the repeated pounding of the poppet flow valve opening/closing. Food grade EPDM solved that problem, but would be far too soft for use in a PCP poppet valve.

[MichaelScholtz]

For those thinking about it. I thought I may be able to pull the standard seal out and flip it over to give me a working solution till I can find the material to make a new valve. - it deformed horribly when I tried to pull it off as gently as possible. it has ridges on the shaft that dig into it, so that's not going to work.

[mikeyb]

For those thinking about it. I thought I may be able to pull the standard seal out and flip it over to give me a working solution till I can find the material to make a new valve. - it deformed horribly when I tried to pull it off as gently as possible. it has ridges on the shaft that dig into it, so that's not going to work.

One of my Liberty parts rifles had a bad poppet seal.
I was able to remove retaining clip and with a little effort (plastic hammer) removed cup.
On a wood lathe (hand drill or drill press should also work) I resurfaced the seal face (still securly attached to the valve stem).
Then reduced (filed) the length of the cup by about 0.03". Put it all back together and initially it still leaked.
Then it self-sealed when pressure got high enough. Others have noted that a few dry-fires would have also "bedded-in" the newly formed seal.
All good with no more leaks since that rework.

A = valve stem
B = valve seal (I "think" it is polyurethane molded to a ribbed valve stem. Safe removal looked unlikely.)
C = steel cup (Keeps seal from distorting under high pressure and holds return spring)
D = cup retaining clip
E = spring

[MichaelScholtz]

I got some delrin from a friend. made a new valve and tried it did actually reseal with higher pressure and a few fires. but I could still hear it leaking a bit

The face was machined straight with a hole in the middle not all the way through for the valve stem.
When I turned the new valve with the valve stem in I noticed it had a slight bend to it.

Could it be that the valve stem is actually bending causing the seal to start leaking.

[darkcharisma]

The counter sunk valve design is the best with peek poppet. Since it will self centered on that counter sunk surface given if the stem is 95-100% straight to the peek poppet. Peek also polish and burnish much better compared to delrin...and it's around $10 per foot on Amazon. Delrin is softer and more porous.

Straight stem, perpendicular poppet to valve and polish/burnish will fix the leak.

[MichaelScholtz]

Ok so I straightened the valve stem to around 1/100th mm refitted and cant hear any air leaking filled it fired a few shots and now im waiting.

I put the valvestem in my lathe and with a dial guage read that it was around 7/10 of a mm off centre
The procedure to get it straight was simply to knock the stem lightly from the direction of the high spot then do a full rotation and repeat until I got it as straight as I could at under 1/100th of  a mm any more would be optimistic.

I havent figured out image posting yet. may film and stick a video on youtube of how I did it, and what I did to make the valve.

Ill need to find peek I do have a nylon tube that may work better than the delrin till I can get peek. bit for now I suspect it will be about as good as it was before.

Incidentally I also put the hammer in the lathe and polished it with 1200 grit and steel wool, then sprayed it with dry molly - its as smooth as silk to cock.

[MichaelScholtz]

Not bad results, as said before it seemed to hold air after a couple of shots to try and seat it.

It lost about 500 overnight so already about half of what it was. so if nothing its better.

Sent about 100 pellets through it today and held up as it should ( haven't chronied it.) but felt fine

Ill fill to around 2000 tonight and then see how it holds overnight now that's its done some work to bed in.

Attached is a quick cad drawing to show how I made it, its not exactly to scale but should give an idea of what I made.

[MichaelScholtz]

OK guys, I did the balloon test on the end of the rifle and my poppet is leaking. How do you get the valve out? I've got the poppet out and the set screw that holds the valve in I think but it will not come out.

Take the hammer and trigger assembly off. With the set screw on the bottom off, tap the back of the valve with a wooden dowel. Tap tap tap but don't smack it.

I went ahead and eliminate the problem all together by having 2mm stem and counter sunk valve face and new poppet.

Im going to give the modified valve a shot.

I got PEEK and (insert your favorite expletive here) it was expensive. 25mm X 100mm bar ( 1" x 3 " ) R190 which is around $20 in value that side.

I have 2 questions:
I'd like to know the angle you countersunk at?
And did you lap the valve with a lapping compound?  ( I'm thinking the stuff they use for brass instruments )

Ive asked the local supplier for prices on the standard valve and brass part to have the original parts on standby should my ambition outweigh my skill.

[darkcharisma]

You don't want a steep angle. Because the steeper the angle the more load you will put on the outside of the poppet. After thousands of cycles it will start to deform. Make it Less than 45 degrees.

I did not need to lap the valve. I used a center drill to cut the counter sunk angle. Then I use a carbide boring tool to adjust the angle to my likings and that gave it a very smooth surface. Laping after that doesnt hurt it but will only help.

 The poppet was drilled (not through) and reamed for 2mm right after it was centered in the lathe, face it and match the angle Of poppet to the valve. Then turn down the other side for spring seat. Then polished smooth with 2000grit sand paper. Then assembled the valve with poppet and lap the two surfaces together with diamond compound that's finer than 2000 grit.

 Peek will require approximately 3000psi or higher to seat well, it will leak at first but dry fire Around 20 shots and check for leak after 4 to 8 hours or over night if you are not in a hurry. You can tell right after 4 hours if it leaks or not.

I actually have the OEM valve on hand while turning the new valve because I don't blueprint anything. It should not be that hard since brass is very easy to work with, just time consuming on setting up and taking measurements every so often. Especially slow when you making The grooves.

[Madd Hatter]

Good info to know Duy.

[MichaelScholtz]

A few days down and a whole lot of pain later.

I suspect I may have nicked the PU ring between the regulator and the block. Its been a royal pain trying to find a suitable replacement. But today I have 2 of them coming to make sure its sealed.

I remade the poppet in PTFE as i wasn't sure the Peek was sealing. it occurred to me that even if its softer i have to tools to make them so something that seals easier even if it doesn't last as long is OK for me.

With the Peek and now the PTFE poppets in the gun still loses all air overnight. Mine I chamfered at 30' to try and get it to seal. if the net ring today doesn't seal the next is to get a replacement original valve assembly. brass and valve.

The tough part is that when you get it wrong you can hear the air leaking, but when you get close the only way to see is to wait it out and see if the pressure drops overnight, and you can't tell from where it leaks.

I'm In South Africa its so far from anything the only place shipping it more expensive is new-zealand and they get left of 1/2 the world maps.
The local importer is very slack in their customer service so getting them to even send me prices on the parts is tough or I would have just got all the o-rings and parts already.

[darkcharisma]

here are the pictures. this seals 100%. no air leaks. potential leak areas are from oring grooves and seal surfaces. to check if it leaks from valve, disassemble the power wheel and dap some soap water to see bubbles. or seal the barrel by having the probe forward and check and muzzle end with soap water. also dunk it in a bucket of water to see bubbles coming off any where along the regulator block.

[Madd Hatter]

I taped a ballon on the end of the barrel. It was inflated some over night so figured the poppet valve was leaking. Duy is making me a replacement.

[darkcharisma]

going to send one out on your BD Robert. 100% sealed and tested, so any leaking problems will need to look elsewhere

[cosmic]

Duy is a great guy all the way around !!

[Madd Hatter]

going to send one out on your BD Robert. 100% sealed and tested, so any leaking problems will need to look elsewhere

Thanks Duy. Look forward to seeing how it works in my rifle.

[MichaelScholtz]

Finally holding air overnight. - and some of my previous poppets probably worked so didn't need to be replaced.

The water with washing up liquid worked, eventually.....

After the seals where replaced and it still leaked slowly I had tried spraying some silicone oil around the areas I thought it could leak from. And that is probably what caused my delay in finding the leak.
yesterday after it losing some pressure overnight again ( around 500 down) I kind of decided I had nothing to loose if I dunk it in a bucket to see where the air comes from. ( I didn't but I was ready too)

In the end I filled a 1lt bottle with water and a bit of washing up liquid ( same as you'd use for checking a slow puncture in a tire) then used a syrings and started squirting it over all areas where the seals I had replaced where. NONE OF THEM LEAKED. i got a little despondent and it then occurred to me it may be a seal that hasnt been replaced.

10 seconds later I saw air leaking from the regulator adjuster....... which I have never touched.
Took it apart again. ( I can strip this thing with my eyes closed now)
I marked the regulator with a paint marker. - as per the advise in Stephen's ( the banker ) video turn out that was good advice. But I also measured the distance to the adjustment with a vernier which was around 2.50mm I removed it and found it had a bit of a molding lip around the ring. I was going to just clean it but I had another ring and just replaced it, greased it and refit it.
I did leave the regulator 1/16 of a turn looser which should up the pressure a bit. But it is marked so I can go back to std. ( Ill start looking for threads on how to measure reg pressure )

So all done its seems much better now. No pressure drop overnight.

So here's what I learned.

Work methodically to find a problem.
Don't forget to check parts you haven't touched.
Figure out how to test all the different parts that could be at fault.
Don't assume that the problem everyone else has or is a common fail point is whats wrong with your gun.
And for good measure - don't take your gun apart to just to see what it looks like inside. ( I didn't till I had a problem but I was SOOOO tempted. )


So now I can move onto fix the low POI problem.

[Madd Hatter]

I received my Poppet valve from Duy today and of course the rifle has stopped leaking! lol I'm still going to install it cause I'm going to be testing Stephen's slugs and I think Duys valve will give higher vel. with everything else being equal. I guess I'm just going to have to grin and bare it (?) and suffer thru the heat in the garage and install that puppy.