Daisy 717 mid-pump hiss

[512k]

Hello there, I'm a new poster although I have been lurking in the shadows for a while

I'm also quite new to airgunning in general, and I've just come into possession of my Granddad's old gear. It all seems to be in good to excellent condition, but hasn't been touched for at least ten years so I'm guessing it will need a bit of TLC to maximise performance.

One of the guns is a Daisy Powerline 717 in .177, which I really enjoy shooting and it seems to be very accurate even in my newbie hands. The lever was originally poorly adjusted so that there was no resistance whatsoever when actuating the pump lever before cocking the bolt. This meant that the lever flapped around a bit when un-pumped and I believe also means the gun was operating at less than maximum power. I've now adjusted it as per the instruction manual. However, after about 50 shots it has developed a slight hiss during the pump stroke, around the point of maximum resistance. This stops once the pump stroke is complete however, and it seems to hold pressure ok.

I'm assuming this means that I'll need to replace at least one seal, but I could be wrong. Can anyone point me in the right direction, or is this actually normal? It only seemed to start happening after I adjusted the pump lever, but I made sure to stay within the specs.

[peteswright]

Just noticed this post. Sorry you've not had any help yet. I can't help as I don't have experience of this pistol but I'm sure someone will be along shortly to give advice. ATB. Pete.

[Benelli B76]

Should be an easy fix, this pistol has an O ring on the pump head and an O ring on the valve body. I could repair it but only work on my own and friends pistols.The only other chap I know who may do it is Lawrie Amatruda who can fix this type of pistol. He is well known on this site.

Baz

[savantguarde]

Its either the o-rings or the valve. if the hiss is coming out of the barrel then its the valve. O-ring wise I have used commonly available o-rings from the box-style kits in a 717 with no problems. if its the valve then it really does require looking at. Although if you are handy I recommend stripping the 717 as its not that complex when you get in there. If you can get someone local to look at it then so much the better but if you are still having trouble drop me a PM. A touch of talc will help you visualize where the air is leaking from (small amount!)

[pcusername]

Before you start stripping it down or getting someone to look at it examine the felt pad on the piston,It's often dry.Soak it with a few drops of pelgun oil.This will get picked up on the piston seal when pumped and lubricate the internals.This often cures a leaky pistol.

[512k]

Many thanks for the pointers, I'll try oil on the felt wiper first and then break out the screwdrivers to check the O-rings and valve if that doesn't sort it. I'm quite comfortable with taking things apart, and yes it doesn't look that tricky to do. No big springs to contend with

[Benelli B76]

You said at the beginning of the thread it holds pressure so it is unlikely to be the valve leaking. To make sure, it is better to check before stripping. Charge up the chamber and leave it for half an hour or so before trying to fire it.

Baz

[512k]

The mystery deepens, the first time I pumped it today it lost all pressure in four or five seconds, giving just a click when I pulled the trigger. Feeling a bit annoyed, I pumped it again and this time it held pressure for a good half an hour and gave the proper pop when I pulled the trigger. I tried again to make sure, and it's now repeatedly holding pressure. How odd.

I've ordered some Pellgun oil, it's possible that this will sort it because I checked the felt pad on the pump and it seems dry. Rather than strip the gun now I'm going to wait for the oil to arrive then try again. Thanks again.

[gingernut]

There is nothing more mysterious than an airgun that has not been used for a long time.
Except a co2 gun that has.

[512k]

Pellgun oil on the felt wiper didn't sort it. The screwdrivers are coming out tomorrow morning.

The hiss seems to be coming from the bolt region so I guess this means it's likely to be the valve body O-ring.

[512k]

Well it's fixed, (and fingers crossed will stay fixed) but I don't quite know what did the trick.

I stripped it without trouble this morning to find, rather puzzlingly, that both O-rings were in good condition and seemed to be well oiled too. Nevertheless I cleaned them up with some cotton buds and then applied a drop of pellgun oil to each, and several drops to the foam wiper behind the piston O-ring which was quite dry. I also took the opportunity to clean out the compression tube.

I then re-assembled the gun, which took *ahem* slightly longer than stripping it, opened the bolt, pumped it... and it still hissed

Then I stripped it again this evening just to double check I'd not missed anything stupid, didn't find anything obvious, put it back together again (much faster than last time ) and pumped it, expecting the hiss, and it had gone. Hurrah!

The only thing I can think of is that the oil needed time to soak into/around the O-rings. Whatever, it's sorted and I'm very grateful for all your advice.