Someone asked me awhile back about the modification I did to my QB valve to accept a standard, polyurethane O-ring and I didn't want to open it up without just cause to take some pics, but today, after many boxes of .22 CP's and nearly two years the inevitable happened...I blew my O-ring valve seal.

So I took these pics of how incredibly easy it was to change the seal. I removed the stock and Maxi-Bulk adaptor. I unscrewed the front of the valve and dumped it out along with the valve stem. I dug out the offending O-ring and replaced it, then put the valve back together. Took under 5 minutes including picture taking.

Here is the valve stem complete with expired O-ring


The new and old o-rings side by side


The modified valve. The factory seal is more elongated so I filed down the shoulder to reveal 50% of the o-ring surface using a dremal and file


The new o-ring installed and hoping for another 2 years and many boxes of pellets. But, if it goes...5 minutes and #11 90 duro polyurethane o-ring


This really is a good way to make the QB more user servicable. The valve seal is just one of many modifiable aspects of this gun that make it a true winner!...Bill

Did you have to modify the Exhaust Valve Body (0410)
so that the new O-ring would fall on a flat?
You can see that little rim in this pic.
Seems like that would have to be flat for the O-ring.

Thanks,
Rich

Yes, Rich, I just BREATHED on it with dremal stone. Thanks for bringing it up cause it's been more than a year and I've slept many times since then. The other factor you reminded me of was that it effectively lengthened the hammer end of the stem. I didn't compensate for this and really didn't notice any adverse effect on performance. I always store the gun with a charge on the valve and the hammer cocked, though.

Any ideas on how I should compendate for the effectively longer stem?...Bill

Humm. Well, the first thing that comes to mind is to shorten it a little.

And that gives me an idea! If I cut mine a little shorter, then when the hammer hits it, it won't be thrown as hard, due to the shorter stroke..?.

That could mean less CO2 get by the seal and perhaps less power! (and noise)!

Might have to try that sometimes.
Rich

Where you were able to purchace the o-ring? Polyurethane o-rings are tough (impossible) to find around here and I really do need a couple. Is it something available at a local level or off the net somewhere? Perhaps others may be able to tell me also.

Charlie

Web Site and Tuning Information:
http://charliedatuna.com/

All of my files are available for download at:
http://charliedatuna.com/

Charlie, I spent a ridiculous amount of time and bucks to find the right ones. I was pretty pissed that I couldn't just call someone to order a freakin' QB seal...but it was worth it...you got mail bud!...Bill

but I thought they did...

We have every size of 1/16" wall 90 durometer urethane orings from #003-016 in stock and many others in 3/32" wall as well.
Any airgun hobbiest will have no problem finding applicatioins for most every size.
003 is QB .177
004 is sheridan 5MM and Career .22
005 is the piercing cap small seal in most of the Crosmans like MKI's and many bolt orings.
007 is a neat breech seal on most QB's.
009 is the size for the Axsor probe orings and the breech seal on all the guns Like the FX that have a .22 caliber barrel and a breech seal fit to a groove in the barrel ID.
010 is an upgrade oring for the foster Quick Connect.
113 is the QB cap and valve oring and also the oring for most Crosman caps.
112 is the inner valve oring for a 150 valve.
111 is the inner valve oring for a 2250 so it has a forever seal on the valve body.
If you buy more than ten orings you can get them for $1.50 each(you can mix numbers to make the 10). I can also make you up kits so you have the most common sizes mainly and a few of the not so common ones.
We sell thousands of orings every year to dealers and hobbiest can get the deal also if they buy right. In small quantities the Urethanes are $2 each plus shipping is $1.
Many outfits sell 90 durometer urethane orings but often 90's will still absorb CO2 and degrade due to absorbtion of the CO2 in liquid state and then exhausting vapor on the low pressure side of the seal and rupturing it as the CO2 hits atmospheric pressure. The CO2 permeates the seal and saturates it.
Parker Seal orings in 90 durometer do not absorb CO2 which means the orings will not degrade. Since the USA made 90 durometer's are Mil spec a 90 isn't a really 90(it is better). I learned this the hard way by redoing a lot of valves for free.
I know what lasts and that's all I'll use. I only carry the finest seals money can buy. When your labor is valuable you cannot let cheap seals cause you redos.
A oring in a valve stem is really not an appropriate application of an oring. The dynamics of orings allows them to move in the groove and make ciontact with two surfaces free of the loading and seal due to the dynamics of the opring movion in the groove.
Using an oring in the place of a gasket just uses an oring as a gasket. It can pop out as it did because it is too soft. The appropriate hardness for the QB mainseal is 70 durometer on the D-Scale of hardness. 90 durometer A-Scale is soft enough to cost you some power. It works because it is soft enough to comply with the surfaces but it won't last and it won't shoot near as hard as a proper pressed in part.

Later

Tim

Tim, I've replied to posts that bellyache about the cost of quality urethane o-rings and have said that your prices are the best there is, without question.

My frustration, along with anyone who's ever lost a seal on thier QB valves is that these things are some kind of mysterious unobtanium. I tried many avenues to get SOMEONE to send me 5 of them so I wouldn't be in this position but it was just frustrating enough to make me figure out a way around the system. Hence the O-ring. I read your entire post above, salivating, thinking you were going to tell me I could just order a half dozen seals for the QB...but you didn't.

What is the big DEAL about getting these seals?...Bill

Most guys when given the seal I use won't have much luck with it because it is very hard and everything must be dead true and lined up.
$5 each for the 70 shore Urethane to go in a QB stem. It can also be thinned and used on the Crosman guns.
Most people send me their stem and I install it for $15. For $30 I'll take your valve and upgrade it to Mac1 specs including all the other seals that go in the QB. I do this on every QB tune that goes thru here.
Most tuners have no desire to use hard material because it is far more demanding to get it to work. Soft is easy and it always seals. Hard material is tougher to get it to work but it last much longer and makes better power.

Later

Tim

Tim, it makes more sense to send in a valve (or stem) and have you do the work than to replace a soft o-ring every couple years but when I'm knee deep in 80-90 degree weather and I lose a valve seal... I just have to keep going...

Do you sell a complete QB valve that's reworked with your seal(gasket)?...Bill

http://www.oringsusa.com/html/oring_kit.html

Rich