Deburring airtube and o-rings questions

[Jaje7654]

Air is leaking from around the gauge on my Crosman 1720T pistol. I removed the gauge and replaced the Teflon tape on the gauge threads with one 1/4" strip 6" long which reduced the leak a lot, but it still leaks. I tried two 1/4" strips at first, but that was too much tape. So the next step is to replace the o-rings on the gauge block. So I need to deburr the airtube to prevent the o-rings from being cut when they are pushed into the airtube.

A 600 grit ball hone would be ideal to deburr the airtube. But ball hones are fairly expensive, and I would use the hone only once. Would 600 grit wet/dry sandpaper or emery cloth be effective at deburring the airtube?

Should I buy the o-rings from theoringstore.com, or is amazon another good source? Which o-ring brands are best?

The pistol is seven years old and has not been fired at all since I bought it. So are there any other o-rings that I should replace?

I know to apply a good amount of o-ring grease to the gauge block o-rings because they will slide down the airtube. Do you apply grease to all o-rings in a pcp or just leave them dry if they are not on a part that slides?

Thanks for any replies.

 

[FuzzyGrub]

Be careful with any deburring. The 1720T and Prod tubes are usually not that bad. Maybe just dull the sharp edge around the inner perimeter of the gauge hole. A ball hone as you describe, would be used in the hammer path, but I wouldn't use it on any of the sealing surfaces.

The O-ring store is a good source, and I have used them many times. I use the HBNR 70D O-rings from them, but NBR 70D will work. 

There are four -113 Orings, valve, gaige block(2), and fill assy. There is one -111 within the valve. That is all the ones that hold air pressure.

I use the yellow gas pipe tape for the gauge NPT threads. White will work, just needs twice as many wraps. I have never measured the length of tape used.

Being it is seven years old, might want to go through the schematic and get all O-rings and a poppet. Poppet and transfer port O-rings best sourced from crosman parts.

Clean the tube before installing, and wipe the insides with silicone oil. Pre-grease all O-rings before installing on the internal parts. Fill the threads in tube with grease. Slowly push each item into the tube. I use a 3/8" OD wooden dowel rod. You can cut a small piece off to compress the O-ring as it goes under the gauge hole.

 

[biohazardman]

Looks Like FuzzyGrub got you fixed up pretty good. I usually use the blue locktight instead of the tape it werqs well and is easy to overcome when you want to remove the gauge. Make sure you let it set up overnight before you pressurize the tube.

 

[Jaje7654]

Is the poppet named "Striker" and part number 1763A036 in the Crosman parts list? 

 

[FuzzyGrub]

On the 1720T schematic, it is in the item 21 valve assembly diagram. Item 21E, Part Number 1700-140, Overmolded valve stem.

 

[Jaje7654]

People recommend #113 70D HNBR O-rings for the 1720T and Prod, but the Crosman parts list shows #113 80D HNBR O-rings. So should I buy #113 70D HNBR O-rings?

Should I buy all the other O-rings directly from Crosman? It looks like the minimum quantity to purchase from theoringstore and elsewhere is very high.

 

[FuzzyGrub]

80D is not common. 70D work fine. You want spares especially if this is your first rebuild.

You can get them from crosman, but the minimum price for any item is $1.15.

 

[Jaje7654]

I want to replace all of the O-rings. Is there an O-ring assortment available that includes all or most of the O-rings on the 1720T? I know that Archer Airguns and Captain O-Ring sell O-ring kits for the 1720T. But I'd rather get a larger assortment from Amazon or wherever because the larger assortments contain hundreds of O-rings for about the same price as the airgun specific kits, and Buna-N O-rings have a fifteen year shelf life from what I understand. I looked at the assortments on Amazon, but it's difficult to tell whether the assortment O-rings match those I need. Thanks. 

 

[Bigragu]

If you have all the sizes known, order from oringsandmore.com.

The first number is the inside dimension, and the second number called out will be the sectional thickness. You can also order the ones standard like the 118’s, 113’s, etc

 

[vdwb]

IMHO Captain O rings is junk. I know the minimum quantities are higher at the o ring store, etc but it’s still cheap, like 3 cents each. A minimum quantity of 100 would be $3.00. Buy your -113 from them and the poppet and transfer port seals from Crosman.

 

[FuzzyGrub]

I order from the O-ring Store and agree with others on price, but understand the ease of ordering a kit. If looking for more choices on kits, the marauder pistol (prod) uses the same kit except doesn’t include the probe O-ring. Try to get one that has extras on the air tube o-rings. You are bound to ruin a couple on your first attempt. 

 

[Jaje7654]

I replaced all the O-rings with HBNR 70D O-rings from The O-ring Store and installed a new poppet and TP seals. I got the poppet and TP seals from Crosman.

I greased all the O-rings with O-ring grease but did not apply any grease on the tube threads. I wrapped the gauge threads with plumber's tape. The gun still has a slow leak. Also, the reading on the gun pressure gauge is far lower than on my new Hill MK4 pump pressure gauge. So should I replace the gun gauge? If so, which brand do you recommend?

Should I fill the threads with grease only for the pressure gauge or all threads in the tube including those for the fill adapter, the screws that hold the valve in place, and the screw that attaches the handle to the tube also?

I took the gun apart after replacing the O-rings because the gun was leaking, but all the O-rings looked fine under a magnifying glass. Thanks.

 

[Saltlake58]

My Marauder had the same problem. The punched parts left burrs on the inside that just tore up o-rings.

I took a the center section of a cleaning rod, wrapped half inch of duct tape on it, then taped some 600 grit sand paper to that. Chucked it into the good old drill and went to town smoothing out the inside of the tube. Once the 600 was done, went to 1000 grit and finished the job. Burrs gone

You are right, use plenty of lube to get the o-rings in. Best part, free because I had everything on hand.

O-Rings from the O-Ring Store? ABSOLUTELY! you can buy enough to rebuild the gun 20 times for less than one rebuild kit on eBay. Really handy when you foul up enough o-rings getting it all back together.

Just my opinion

 

[Jaje7654]

I replaced the gauge with a Crosman pressure gauge, and now it's no longer leaking.