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jschonfarber · Post by **jschonfarber** » Sat Sep 21, 2013 8:26 pm

I have a daisy Avanti 887 that won't fire pellets completely out of the barrel. I think the problem is that the hammer is not hitting the valve hard enough to let enough CO2 out for it to fire correctly. I have tried replacing the mainspring but it doesn't help. I have also tried shimming the mainspring to make the hammer hit the valve a little harder but the spring compresses too much and doesn't allow the action to function properly most of the time but, when it does it still won't fire completely. Any ideas would be appreciated.

jhmartin · Post by **jhmartin** » Sun Sep 22, 2013 9:33 am

The only times I've seen this happen are:
1) when the temperature is very warm (>98F) or the cylinders are left in the hot sun ... The CO2 pressure gets so high that the hammer cannot function the spring/valve.
--or--
2) when the cylinder is overfilled and there is no room for the CO2 to expand into a gaseous state in the cylinder. Do you weigh the cylinders when you fill them? Max should be about 475 grams. With a full fill like this you can easily fire 2 3x20 matches

If you are losing/popping the burst disks that's a big indicator, but that does not always happen.

Also, is the relief plug still in the bottom of the action? If this is loose or gone all of the gas goes out that bottom hole.

Worst case, take the action out of the stock, take the sights off and send it back to Daisy ... they can (and do) accomplish the repairs to the 888/887s pretty quickly. Unfortunately, as you probably know, that valve assembly is pinned and is very difficult to get off

jschonfarber · Post by **jschonfarber** » Sun Sep 22, 2013 4:01 pm

I have tried several cylinders filled anywhere from 460 to 480 grams and all chilled. I didn't think about the relief plug and I'll check that thanks I'll let you know how it turns out.

jschonfarber · Post by **jschonfarber** » Thu Sep 26, 2013 5:42 pm

I checked the relief valve and it there was no leak as far as I could tell. Do you think that a stronger mainspring or a heavier hammer might help?

jhmartin · Post by **jhmartin** » Thu Sep 26, 2013 5:55 pm

jschonfarber wrote:I checked the relief valve and it there was no leak as far as I could tell. Do you think that a stronger mainspring or a heavier hammer might help?

A heavier hammer won't work as the spring still has to accelerate it to the valve. You can try stretching the mainspring a tad, but if you've already shimmed it I don't see that working either.

Have you lubricated the valve? I use the "Air Venturi MP-5" oil from pyramid air for this. It is an extremely light oil for airguns and we also use this to lube the o-rings on the cylinders.

I take the action out of the stock, and take the trigger assembly off the rifle so that you have access to the valve nib where the hammer strikes it.
I hold the gun vertical (muzzle up) and drip 5-10 drops of the MP-5 oil into the cup where the cylinder screws in. Then press the nib and let the oil flow in ... let it soak like that about 10-15 minutes.
THEN -- don't do this next part indoors!

Again holding the muzzle up put a few more drops into the cup and install a cylinder with CO2 in it. I use a small ball peen hammer to tap the nib (like the regular hammer would do) to "pop" the oil out of the valve a few times. Take the cylinder out and repeat.

I do this also when I have a slow leak in the valve and I suspect some dirt or dust is keeping the valve partly open.