More woes with my sumatra carbine :-(

[WILBA]

take the stock/ shroud off, remove end cap and spring, check power adjuster is not buggered.. or just unscrew the course threaded collar and remove. if it still won't fire get a large puch and a small hammer and the tap the vale stem directly.

If it is the valve stem what could have caused it to happen? Maybe it was not the hammer spring last time then jon? Would fitting the uprated valve stem cure it if it is the valve stem jon?

[Shed tuner]

need to see what the problem is first.

if the valve stem is getting stuck, it could be the profile of the mushroom head, somehow settling into and jamming into the valve face itself. But that would be unnusual, unless it's been previously modified, or made from a dodgy batch.. the material is delrin like. Maybe it could save some grease of something sticking in there ? Or an excessively heavy valve return spring. It's quite weird.. see if a few taps frees it up first.

Then again, maybe it could be as simple as a bent stem.. trouble is, if the stem was that bent, I wouldn't expect the head to seal. and those stems are thick / heavy duty as standard.

Puzzling.

[JLB]

Is it possible that something has come adrift at the valve return spring end, a strip down seems the only way to get to the bottom of it in my opinion.

John

[WILBA]

need to see what the problem is first.

if the valve stem is getting stuck, it could be the profile of the mushroom head, somehow settling into and jamming into the valve face itself. But that would be unnusual, unless it's been previously modified, or made from a dodgy batch.. the material is delrin like. Maybe it could save some grease of something sticking in there ? Or an excessively heavy valve return spring. It's quite weird.. see if a few taps frees it up first.

Then again, maybe it could be as simple as a bent stem.. trouble is, if the stem was that bent, I wouldn't expect the head to seal. and those stems are thick / heavy duty as standard.

Puzzling.

I changed the hsmmer spring to a predetor heavy duty one last year as fitting a heavier hammer spring fixed this problem on tinbums gun as it had the exact same problem but makes the gun a bugger to cock. Has been working fine up to now. Am i right i. thinking the hammer runs dry as in all other pcp's jon? Is it the hammer or valve face delrin jon as you confused me a bit. Chris

[rovercoupe]

Could it have had the valve messed with in the past and now it takes a real heavy spring to open it and the transfer port is doing it’s job of restricting the power back down to sub 12 levels?

[Shed tuner]

the valve is steel. the hammer is steel. the mushroom head on the valve stem is synthetic (delrin ?), encased in brass. the (inner) valve face is steel.

so the only way it cannot fire is if the valve stem delrin mushroom is not being knocked away from the sealing face of the valve. generally, the only things that hold it in place are air pressure (hence you pressure lock situation) and the valve return spring.

this is why I suggested the power adjuster (which limits and can block) valve stem travel be checked first.

[WILBA]

Could it have had the valve messed with in the past and now it takes a real heavy spring to open it and the transfer port is doing it’s job of restricting the power back down to sub 12 levels?

Gun has not been messed with i know that.

[rovercoupe]

Hmm,just a thought but does it have a plastic restrictor on the valve stem? Could this have swollen and it’s stopping the hammer from getting to the stem?

[Shed tuner]

Hmm,just a thought but does it have a plastic restrictor on the valve stem? Could this have swollen and it’s stopping the hammer from getting to the stem?

or somehow jammed.. yeah, good point.

[WILBA]

Hmm,just a thought but does it have a plastic restrictor on the valve stem? Could this have swollen and it’s stopping the hammer from getting to the stem?

What does the restrictor look like as i hsve no idea what i am looking for.