Hatsan Jet

[Texpatriate]

site glass on the gauge. That suggests the gauge rather than the plumbing.

[Rob M]

just plug the gauge hole james and see how it goes overnight , wont take long to whip up an m10 plug

[JPSAXNC]

It turns out the bubbles I saw at the edge of the site glass were coming from between the site glass and a piece of thin plastic protective coating, which peeled right off. Re-charged the air cylinder, gauge needle hasn't budged all day. So the leak is in the valve or foster fitting, But I didn't see a single bubble anywhere, I held the parts under water, I turned them every which way, I shook them around, Nothing. I don't see how the leak can be big enough to watch the needle progress downwards over time but not big enough to make any bubbles?

[Back_Roads]

 Wonder if the hammer spring is putting pressure on the valve enough to cause a leak, try a leak down test with the gun cocked

[JPSAXNC]

James, I think you nailed it. I installed a stiffer valve return spring, and the gun is still holding a full charge,

[EdinGa]

I got my Crosman poppet and stem yesterday but  4mm Amazon reamer that was supposed to arrive today didn't ship until this morning.


I'm going to see it I can find a weaker hammer spring for mine since I'm not going for power. Even if my valve leaks a little, it shouldn't be a huge problem since I'm running the ASA adapter with an on/off valve.

[JPSAXNC]

Another string, 18 shots 14.3 cphp's  619 621 626 619 631 631 630 628 622 625 627 626 624 629 625 619 619 619. Not many shots, but the flattest string I've shot in .22 in this velocity range.

[JPSAXNC]

Here's 28 shots enough for 4 magazines. 14.3 cphp's   586 578 589 592 586 596 594 590 592 586 593 588 598 593 593 596 596 590 590 589 588 588 589 587 586 586 584 585.

[Back_Roads]

Here's 28 shots enough for 4 magazines. 14.3 cphp's   586 578 589 592 586 596 594 590 592 586 593 588 598 593 593 596 596 590 590 589 588 588 589 587 586 586 584 585.

Sweet right up there with the old Prod tunes.

[JPSAXNC]

Thanks, I'm thinking of leaving the tune right where it is. I'm using the OEM hammer spring again. The new valve return spring is wound from .038 wire with a .160 ID. the OEM valve spring is wound from .023, so it's a huge difference in spring rate. The stock spring takes about 1 1/2 -2 lbs. to unseat the poppet, the new spring about 8-9 lbs. which seems like a lot, but it really flattens the string. I'm using Motorheads 15 degree valve seat with a .250 OD. flat faced poppet, with a .338 OD. metering lip. These mods would likely cause an OEM valve stem to break. I hope a useful substitute can be found.

[Rob M]

I got my Crosman poppet and stem yesterday but  4mm Amazon reamer that was supposed to arrive today didn't ship until this morning.


I'm going to see it I can find a weaker hammer spring for mine since I'm not going for power. Even if my valve leaks a little, it shouldn't be a huge problem since I'm running the ASA adapter with an on/off valve.

any luck on the reamer???

[EdinGa]

I got my Crosman poppet and stem yesterday but  4mm Amazon reamer that was supposed to arrive today didn't ship until this morning.


I'm going to see it I can find a weaker hammer spring for mine since I'm not going for power. Even if my valve leaks a little, it shouldn't be a huge problem since I'm running the ASA adapter with an on/off valve.

any luck on the reamer???

I got it and started shaping the poppet, but I'm not sure it's going to work. There's a metal flange or washer inside of it, and I'm afraid it's going to come apart before I can get the diameter small enough.

[Rob M]

that metal flange should seal to the jet nylon seat , so long as its smooth enough

[JPSAXNC]

Did you try to see if the stem would go into the valve?

[EdinGa]

that metal flange should seal to the jet nylon seat , so long as its smooth enough

I hope so.

[EdinGa]

that metal flange should seal to the jet nylon seat , so long as its smooth enough

Double post

[EdinGa]

Did you try to see if the stem would go into the valve?

It was too tight before I reamed the valve to 4mm, but it fits now. I ran out of time today, but I'll try to get it finished soon.

[EdinGa]

Well, back to square one... The Discovery poppet and stem is a bust for the Jet.

[JPSAXNC]

I made a replacement  poppet and stem that will fit your 4mm. hole. If you want it, PM me your mailing address

[Rob M]

Well, back to square one... The Discovery poppet and stem is a bust for the Jet.

i see now the metal seperated,, darn