Mushroom Man
A very nice .22 pump-up rifle similar to the Silver and Blue Streak models.
At rest the pump handle flops down. There is no adjustment on the pump rod and none shown on the instruction book, even though I note that some of the same model listed an adjustable pump.
But: with a few pumps or more(say 3 or more) the pump handle stays where it should be for about 15 seconds before once again flopping open.
I thought it could be the link spring but am not so sure now and wonder if this is a sign of a slow air leak that is allowing the pump handle to go 'out of tension'. The rifle still fires at the 'flop' point so the leak cannot be that bad and we can get a reasonably respectable 520 fps out of the old girl with 6 pumps.
Has anyone had a similar experience? What was the cause? The rifle is really in excellent condition apart from this flop and looks far more tasty than the un-chequered Silver and Blue Streak models. It even has a medallion on the stock declaring it to be American Walnut.
Cheers, Phil
Registered User
Just a wild guess, but is it possible that a prior owner lost the locking nut from the pushrod and just screwed it into the plunger until it stopped?
I have a 317 and a 312, both have adjustment at the lever end of the pump, the pushrod screws into the plunger and is locked by a nut.
At the seal end the pushrod just screws directly into a blind hole.
The pump seal pressing on the valve face is what keeps the lever up, with or without pressure.
Is your pump assembly not screwed together?
Mushroom Man
Thanks for the comments magicesperanto.
The instruction book we have does not show any adjustment to the pump rod ... no adjusting nut etc. Parts are not shown on the exploded diagram. But a manual I have downloaded does show the adjustment nut etc.
Maybe there were two versions of the rifle over the years.
But if the adjustment was the cause for the 'flop' why should the flop go when 3 or more pumps are put in? And why does the lever flop down after a short while? I can only think of an air pressure problem. I intend to pump the rifle and leave it to see if the pressure drops over time....
Interestingly, the manual that came with the rifle gives instructions on resealing it. You could buy the tools from Benjamin.
Cheers, Phil
Registered User
Well there are two pressures, the pressure within the main valve which is used to fire the slug, and a residual pressure between the pump seal and the valve face.Originally Posted by Phil Russell
The pressure in the main valve should not leak back, but the residual may leak away, which explains why it drops down after a while.
It is possible that you are missing a spring from the pump lever.
Mushroom Man
Thanks magicesperanto ... I am learning ... I had not thought of two pressures and the more I think about it now, you could be right as:
If I pump the rifle slowly there is virtually no compression, even with 6 - 8 pumps. Only when the rifle is pumped quite briskly does it pump up, getting progressively more difficult as expected.
The time lag for the pump handle to flop also depends on the number of brisk pumps used: more brisk pumps and the handle stays put longer. I have added 6 brisk pumps and left the rifle for 30 minutes as I would expect a leaky inlet/outlet valve to have lost considerable pressure by then. But this has not happened: there is still a healthy crack when firing the pellet.
These facts make me think that the pump head is worn and needs replacing.
(I believe I can see the link spring).
So ... anyone know of a place to get one? Or do I start ringing around?
Cheers, Phil
Registered User
You could try here: http://www.bryanandac.com/
Some years ago I got a seal kit from them, they were good to deal with, but postage stung a bit.
Posting Permissions
Reply With Quote