Issue installing Huma Reg, Leaking on my 1720T

[sobdiver]

Today I attempted to install a Huma Reg in my 1720T.   I removed the gauge block, then put in the plenum, followed by the reg.  After filling I can hear the air leaking  (and feel with my finger) out of the old gauge port hole pictured.



I tried removing and reinstalling, adding a little more silicone grease,  flipping over the plenum. tapping everything in harder,  and nothing worked.  I've inspected the o-rings and they look fine.   I just emailed Huma and thought I would reach out here as well.

[vdwb]

You might have to remove the valve and make sure it is flat and square where the reg plenum mates to the valve. It sounds like the o ring is not sealing between the valve and plenum. You will get some leakage from the gauge block hole when filling and the reg vents and equalizes.

[sobdiver]

You might have to remove the valve and make sure it is flat and square where the reg plenum mates to the valve. It sounds like the o ring is not sealing between the valve and plenum. You will get some leakage from the gauge block hole when filling and the reg vents and equalizes.

That would make sense that the oring isn't sealing there. But, if the valve is out of square, I'm not sure how I would fix that as it can only screw in one way.  I did replace the gauge block and got the Huma to work with the gauge block in place, but the shot count was very poor. 3000 psi to 1400 psi (off reg) only got about 10 shots, 780fps avg, 8.4's.  Probably a little easier to tune with the gauge in place, but don't want to spin my wheels too much if I'm not going to be able to get it work without the gauge block.

[Jaybird 4328]

Have you drilled out one of the TP's.I drilled mine to .113",I kept the gauge and block and set the huma to 120 bar.I get about 25 shots at 840-850 fps with 8.4gr's.I also clipped a few coils of the hammer spring and a lighter valve spring.

[FuzzyGrub]

The O-rings on the plenum are fairly protected from the gauge hole, but it is possible one was knicked.  Also, carefully check the one on the reg, it might have been damaged by pushing it over the fill assy threads.  If the threads are very sharp, dull with fine sandpaper and clean.  Silicone grease the threads before inserting each part. 

Pull the valve and look/feel the surface.  Maybe some silicone grease is holding some crud to the surface.  Maybe that aluminum spacer that is between gauge block and valve, scratched the surface of valve. 

Assemble just the tube and test, before doing the rest of the gun. 

Hope that leads you to the culprit.

[RDB]

Also, if you have an assortment of orings. Try a thicker one at each end of the plenum. Mine would leak there.  I ended up having to sand each end of the plenum so the orings would compress enough and seal up.

[sobdiver]

A new day: I carefully read each post, plus the response from Huma and decided that before a tear down and removing the valve for inspection I would try one last time.  This time though I took a q-tip, taped it to a skewer, put on some rubbing alcohol and wiped down the "valve" face.  Reassembled and it still leaked.  So I removed the HUMA, slid out the plenum (for about the 10th time), and then stared at my hand in dumfounded disbelief when in addition to the Huma plenum a second small plenum slid out this time. 



I reassembled without the small crosman plenum and there doesn't seem to be a leak this time.

[FuzzyGrub]

A new day: I carefully read each post, plus the response from Huma and decided that before a tear down and removing the valve for inspection I would try one last time.  This time though I took a q-tip, taped it to a skewer, put on some rubbing alcohol and wiped down the "valve" face.  Reassembled and it still leaked.  So I removed the HUMA, slid out the plenum (for about the 10th time), and then stared at my hand in dumfounded disbelief when in addition to the Huma plenum a second small plenum slid out this time. 



I reassembled without the small crosman plenum and there doesn't seem to be a leak this time.

That is the spacer I mentioned.  You found the problem.     That does not get installed when using the huma plenum/reg. 

[RDB]

Good deal! If you need some help tuning it , hit us up.  If you open up the valve and t-port. You should get darn close, if not 40 shots with the 8.4 @ 800 fps.

[sobdiver]

Good deal! If you need some help tuning it , hit us up.  If you open up the valve and t-port. You should get darn close, if not 40 shots with the 8.4 @ 800 fps.

Yes, any tuning tips would be most appreciated.  I opened the transfer port to .116, but haven't touched the valve.  I took a photo while I had things disassembled when I realized that opening up the transfer port larger than the valve probably didn't do much.   Are there any tips for drilling out the valve?   Probably needs to be removed and disassembled? I wouldn't want to get metal dust inside the valve or hit that spring I see.



Previously, I had a pretty good B-Staley tune with the gun.  TP at .097 (probably could have left it there if I wasn't going to open the valve) I also have a hammer spring that is a little stiffer and shorter than stock:



On my bstaley tune, 5.5 turns on the new spring, equaled about 7 turns on the stock spring in terms of FPS from what I remember.

Initial testing on my new Huma, seems to be very inefficent.  Set at about 95 bar,  spring at 5.5, stroke at 2, very poor shot count.  Just now tried spring at 5.5, stroke at 4, shot count still seems very poor.  Before enlarging the valve further I would like to see what I can accomplish with the current setup.  Shooting 8.4's close to 800fps for any kind of decent shot count would be a nice goal.    So any tips on stroke and spring preload setting, best way to open valve, or anything else would be very helpful.  Thanks!

[sobdiver]

Ok, I removed and disambeled the valve, was pretty easy.  Now getting ready to drill out the valve to match the transfer port, unless someone stops me in the next few minutes .  Barrel opening is .12, I don't have have .12 bit, but have a #32 .116, which is the current TP.

[sobdiver]

[RDB]

Open it up. But make sure you dont go bigger than the t port o ring.  You'll need a shoulder for it to seal on.

Use your shorter stiffer spring. Run the stroke way out and lean on the hammer to bring the velocity up.  In other words, you want a very short stroke and a hard tap on the valve.

You'll immediately hear the difference in the shot cycle.  The farts will disappear.

90-95 bar is perfect.   Make sure your valve is completely clean of any and all shavings.

[sobdiver]

Open it up. But make sure you dont go bigger than the t port o ring.  You'll need a shoulder for it to seal on.

Use your shorter stiffer spring. Run the stroke way out and lean on the hammer to bring the velocity up.  In other words, you want a very short stroke and a hard tap on the valve.

You'll immediately hear the difference in the shot cycle.  The farts will disappear.

90-95 bar is perfect.   Make sure your valve is completely clean of any and all shavings.

Thanks for the tips! Now we are making some progress.  I opened the valve and TP to .122 (caliper reading),  I maxed out my hammer spring at 7 turns (the shorter stiffer one) and tested some different stroke adjustments.  At 9 1/2 turns I got about 27 shots before falling off reg with 8.4's, FPS AVG 780.  At 10 turns on the stroke it fell of the reg at about 31 shots, 8.4's and 770FPS AVG.  If I went any higher than 10 on the stroke the FPS really started to drop a lot.  Some good progress and wondering what else I can try next.  My SCUBA tank is starting to dip below 3000, so can't quite fill all the way to 3k, but close.

[RDB]

Its just a balancing act now. You may find 8 1/2 on the throw and and less hammer nets you more shots. If you make 35 shots I'd call it good and enjoy it for a while.  At least you can (hear) the difference in the shot cycle now and tell if its getting better or worse.  780-790 seems to be the sweet spot for me also.

A lightweight hammer would definitely help bring the shot count up. But sourcing a hammer without sending it in to a tuner may be difficult.  I get 48 shots on the reg with the 8.4's.

[sobdiver]

Its just a balancing act now. You may find 8 1/2 on the throw and and less hammer nets you more shots. If you make 35 shots I'd call it good and enjoy it for a while.  At least you can (hear) the difference in the shot cycle now and tell if its getting better or worse.  780-790 seems to be the sweet spot for me also.

A lightweight hammer would definitely help bring the shot count up. But sourcing a hammer without sending it in to a tuner may be difficult.  I get 48 shots on the reg with the 8.4's.

I have some feelers out for a lightweight hammer, it's something I would like to try.   I'm also wondering if this spring might be worth trying: https://www.mcmaster.com/springs/length~1-1-2/od~0-3/wire-diameter~0-042/finish~zinc-plated/  I've also heard mention of a lighter valve spring, but not sure of recommendations.   You must have a lightweight hammer, correct?

[Jaybird 4328]

Check out Hillairgun.com.He has great stuff and he can help you what you want to do.

[sobdiver]

I'm getting pretty dialed in on a tune.  At 9 turns clockwise on the stroke and 4 turns clockwise on the spring, for the first time I obtained a rising FPS when it went off the Reg,  The gun was also nice and quiet.  I turned the spring about another quarter turn clockwise and then:

Stroke 9 turns clockwise, Spring 4 1/4 turns clockwise,  FPS AVG, 785, went off reg around shot 33 - 772, 34 - 766 35 - 757.  JSB 8.4's.  But here's the thing, my beginning fill was only to 2700 psi since my refill tank is that low.  So, I think I can add at least 6 or more shots if I had started at 3000psi,  which would put me right at 40 shots and 11.5 FPE.

[RDB]

Sounds like your there. Good deal. Who would have thought you could get that many shots out of that tiny air tube?