Sunday, October 9, 2011

Aeron B96 CO2 Leak Quick Fix

Was down in Tennessee on vacation last week and one of the pistols--the Aeron B96--developed a very small leak.  I did an easy field repair and had no further problems, but now I'm home and it's time to make sure it's right.

The leak was coming from the top of the gas tube under the grip.

This cylindrical tool came with the pistol.  The internal boss fits a notch on the CO2 cap.

The cap removed.  The tool works for both the 12 gram cap as well as the bulk-fill.  I'm thinking its best to do this after shooting all the CO2 out of the gun first.

The opposite end of the tool has two pegs

This fits into the grip (over the gas tube)...

...and engages the notches on the grip retaining lock ring.

The entire grip slides off as a unit.

The two allen head bolts on the gas tube attach the tube to the frame. 

Of course, they're metric.  They need a 3mm allen wrench.


Gas tube pulls right off.  Note the CO2 transfer port just right of my index finger.

One of the side benefits of using Crosman Pellgun oil is relatively simple leak detection.  This is clean now, but when taken apart last week, there was an obvious oil leak here. 

The ring was pretty beat.  I'm sure it's metric, but I'm not able to accurately measure it in this worn condition. 

Found a couple o-rings that looked like they'd fit the bill.  They're 5mm OD and 2mm thick.  Only the o-ring on the left side is critical to sealing.  Chose something that fits the counterbored hole in diameter and is a bit higher than the edge of the frame.  It'll squash and seal when the lower bolt is tightened.  The right side o-ring simply seals the underside of the allen bolt to the frame.  It really only needs fit under the head of the fastener to work.  I ended up wrapping the lower bolt threads with a couple layers of teflon tape as added insurance.  Greased the o-rings with a silicone dive grease. 

The top bolt allows for grip angle adjustment.  Wish there was an index scale on the side to repeat the angle adjustment.  OK, I really wish I'd thought ahead and marked a reference line.  I'll just have to shoot it and adjust if/as needed.  Yep.  Tough job.

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