How to Fix a Liberty / Freedom / Aspen Valve Poppet

[FuzzyGrub]

The ATI Nova Liberty has been available in the states for almost a year now.  It has allot of great features at a value price.   It has a good following of owners here on GTA, with many members sharing their experiences, modifications, and tweaking.  Notably Stephen, Duy, Ray, and a list of others. 

To date, it seems like the main weak point of this gun, is the poppet.  The material is rather soft for a PCP operating at 2Kpsi and higher.  A number of people have had poppet leaks from the get go, and others have experienced them when they raise the regulator pressure or other power mods.   The two poppets I have repaired, had deep imprints in them from the valve seat and the metal can was flush with the valve face. 

As of this date, spare parts are not available yet from ATI, the USA Importer, or Nova Vista, the Chinese manufacturer.  This fix will be an improvement over the original material, and should last much longer.  This repair will uses Delrin/acetal rod for the repair.  This material is harder than the OEM and it is easy to work with.  It is commonly used in other brands of PCP airguns, operating in the 2k - 3k psi range.  Common examples being Crosman Mrod, Prod, and 1720T. 

This thread will document how I performed the repair, without a lathe or other expensive equipment.  The main tools, being a couple of hand drills.  I will try to detail the steps such that other mechanically inclined DIYer's can perform this repair/fix. 

Note: This was done specifically for the Nova Liberty, but it is my understanding that the Nova Freedom (ATI), and Seneca Aspen (PA) use the same poppet. 

Note2: This was originally discussed in this Thread, by Will: https://www.gatewaytoairguns.org/GTA/index.php?topic=162313.0   Will

[FuzzyGrub]

Material: 5/16" Delrin/Acetal Rod, a three inch piece is more than sufficient.  Commonly found in 1 foot increments:

Colors, can be black, white, off white, or tan, maybe others.  You won't be able to see it, so doesn't matter much. 

[FuzzyGrub]

Tools:

- Two hand drills, 3/8" minimum.  One being 1/2" with a key chuck is preferred
- Number Drill Set:  Harbor Freight is fine: https://www.harborfreight.com/60-pc-titanium-high-speed-steel-numbered-drill-bit-set-61690.html  These are good to have for many PCP airgun mods.
- Calipers
- (&#^((&^* File (Bassturd)
- Grades of Sandpaper 220, 320, 400, 600
- Vice
- Single Edge Razer Blade
- Fine Tooth Hacksaw Blade
- Epoxy Plastic Binder
- Assorted Pliers
- Misc stuff  

[FuzzyGrub]

It the first picture you will see the oem poppet with the deep embedded seat mark.

The second picture shows the components of the poppet, metal can, hardened stem, C-clip, and shavings of the original material.

The third and forth picture provides the key measurements of the metal can and stem, as measured with a HF caliper.   

[FuzzyGrub]

The first step is to degass the gun, dis-assemble, and remove the poppet.  I'm not going into that here, but Stephen (thebanker4 on GTA) has a good video on his Air Velocity Sport, Youtube channel:

Once you have the poppet out, you need to dis-assemble it.  You need to remove the C-clip on top of the metal can.  A combination of a large flat bladed screw driver and pliers will get it off. 

Once the clip is removed try lifting the can off.  It may just slide of or may need some heat for encouragement.  I used a bic grill lighter, but a candle, heat gun, etc would work.

Next, I sliced away the old material with a single sided razer blade.  This took a few passes to get down to the stem, and get all the pieces removed. 

I cleaned the stem in Isopropyl alcohol, but brake cleaner or other degreaser will suffice.   

[FuzzyGrub]

Cut off a 3" section of the Delrin/acetal rod, to work with.  You can chuck it up in the drill and use the hacksaw blade at perpendicular angle to cut it off.  Cut the 3" piece at the drill end to keep the rod from flexing too much.  While this cut doesn't need to be precise, practice for latter.  ie try to make it as square as possible.  I put an initial groove in the rod, with the saw teeth pointed in the direction of travel.  Once there was a groove, reversed blade so teeth were against rotation.  Try to hold the blade as steady as possible, the blade will try to make small jumps.

If you are using 5/16" OD rod, you do not have to turn it down.  My first two poppets were repaired with 3/8" rod that I turned down with 220 grit sandpaper wrapped around a bassturd file.   You will see the taper in the picture below.  Also note, the pilot hole is already showing.  This was from making the 1st one, and will cover how to do that, next.

[FuzzyGrub]

To make the pilot hole, I used the metal can as a template.  I slide it over the end of the rod.  I chucked up a #32 (0.113") drill bit in a second drill.  You only spin the Delrin rod, and just hold the chuck that the drill bit is in.  Feed the drill bit slowly, keeping everything as straight as possible.  I went to about one inch in depth, deep enough for a couple of poppet.  I don't know if I just got lucky, or the action of the rod spinning helped keep the hole centered. 

Once the pilot hole is complete, remove the metal can.  Incrementally, step through number drills #31 to #22.  Again, only spin the rod.  This keeps the hole as centered as the pilot hole.   After the #22 drill, the hole should be close to 0.154" ID.   This gives about 0.012" of interference with the rings on the stem.  It provides a good tight fit. 

[FuzzyGrub]

The next step is to square and polish the end of the rod.  This will become the sealing side.  Use a bassturd file wrapped with a small piece of sandpaper.  Start with 220 grit, followed by 320 -> 400 -> 600. 

Un chuck the rod and chuck up the metal can with the edge facing outward.  We need to take 20 thousands off of it.  I used the bassturd file until I reached the dimension.  Then polished with the same sandpaper routine as above.  I marked the edge with a black sharpie, before removing any metal.  That makes it easier to judge how much you have removed, and lessons the number of time removing it to measure.

[FuzzyGrub]

Chuck up the Delrin rod again, with the polished end facing out.  Place the metal cap over the polished end.  While spinning, mark the rod with sharpie, about 30-40 thousands past the lip of the can.  This will be a reference for cutting it.  You don't want it too close to the finished depth (0.020" below can edge or too far away that you have allot of sanding to get back to that measurement. 

While spinning, use the hacksaw blade with the teeth pointed in the direction of rotation.  Once there is a groove, reverse the blade, keeping it square and perpendicular, slowly cut the rod.  Hold the blade as steady as possible, as it tends to "jump" a little. 

If you have a 1/2" drill with a keyed chuck, you can us it to sand to correct height.  The keyless chucks pictured could not hold the poppet material and still extend out far enough to work on it.  In that case, you can resort to flat sanding it on a table. 

When at correct height, insert it in the metal can with the original polished surface on the outside.

[FuzzyGrub]

Next is pressing the stem into the poppet material.  I used a drill press vice, but any vice that can open 2.5 to 3" should be fine.

Press the stem in such that it is even with the back side of the metal can.  Make sure it is as straight as possible, or parts might fly out into never find them land.

Next, find a spacer, such that you can press the stem on through.  A stack of washers, some metal tubing, or what I found laying around, a riv nut.  Set it up, but don't press it in yet.

[FuzzyGrub]

While I don't know if it is necessary, I used epoxy plastic binder on the knurled ends of the stem.  I had this from fixing a dishwasher tub, which has held up over a year.  I tested it on some of the Delrin, and once dry seems to adhere to it well.  It only takes a small dab, and used a toothpick to apply around the knurls.   Press the stem in the rest of the way, until the backside of the cone contacts the Delrin, and the c-clip groove is fully exposed.  Remove it from the vice and clean off any epoxy that is on the outside.

[FuzzyGrub]

Re-install the C-clip, and that is about it. 

If anyone wants to give it a go, please IM msg me and will help with any clarifications or further suggestion. 

[SoCalZac]

Wow thank you awesome write up!!

[wll2506]

John,

An absolutely brilliant write up and how to for a poppet fix on the Liberty, Aspen or Freedom ... this should be a sticky for sure.

Anyone that has one of these guns needs to read this as they will have issues with Nova's poorly designed poppet down the line.

Again great job, I applaud you ;- )

wll

[Stikkershokk]

With 2 Freedoms  and a Liberty, it looks like I might be returning to this article at some point. Thanks.

[Wayne52]

Very nice step by step instructions and pictorials on revamping of the poppet Steve, this thread will definitely be getting bookmarked on this puter.

[FuzzyGrub]

Thx for all the positive comments.  .

I have one more gun to do, maybe two, and best to document before I start forgetting details.  Those will use the 5/16” rod. 

[AVS Stephen]

Wow, John that was awesome. I'm going try it for heck of it. Thanks for that Tutorial.

BTW...Your bench looks like mine...I know you know where every thing is....LOL

[anti-squirrel]

definitely a good tutorial- thank you for sharing

[FuzzyGrub]

Wow, John that was awesome. I'm going try it for heck of it. Thanks for that Tutorial.

BTW...Your bench looks like mine...I know you know where every thing is....LOL

Yep, its there somewhere on the bench!   

Let me know if you have any questions.