Saturday, March 12, 2011

Overhauling a Crosman 160 Part 2

Right back into the action...

The smashed flat transfer port o-ring needed a dental pick for removal.

Banged the end of the gas tube on the bench and the valve slid out.

Had to tap the plug out with a dowel rod.

Here's the stud I dislike so much. I wasn't going to countersink the fastener--then I was--now I'm not--for now. I've got another project coming in that is somewhat time sensitive (self-imposed) so I've got to get this gun finished.

In the mean time, I will make a duplicate stud as I don't want to re-use the thread damaged original. A piece of 0.250" drill rod was hacksawed to length.

Cleaned up the ends and used the Taig tailstock die holder to start 1/4"-28 threads on each end.

Finished the threading by hand with a proper die holder and the piece in the vise, then back to the Taig lathe to face the ends down to a final length of 1.885".

I'll blue this later to match.

Took the cover plate off the trigger. Nothing was wrong with it, but since I was this far into the gun, it made sense to check everything.

A few pics for parts orientation so I can reassemble it later.

Top set screw handles sear engagement, middle is the trigger stop and bottom is weight of pull.

The sear is potentially the only trigger component that can give you trouble on reassembly.

The spring, the two small pins, and the sear's three contact points could be a bit confusing.

So I took a few more pics--especially of the spring orientation.

And just like that, the battered trigger housing was stripped and repainted as I began its reassembly.

Once the sear was installed correctly, the rest of the parts drop right in. Used Buzzy's Slick Honey on all the metal to metal contact points. I also polished all the contact points.

Side plate reattached and set the trigger unit aside for later.

Here's how the valve tool interfaces on the valve face inside the gas tube.

As the face of the valve is tightened, the o-ring in the middle of the valve body expands outward sealing the tube. (The rear of the valve is anchored in the tube so it can't rotate as the front is tightened.) The strip of steel for the tool measures 0.131" thick, 0.736" wide and 8" OAL. If you have something close, it'll work, though it may take a couple minutes with a file.

It's sometimes necessary to clamp half of the valve in rubber or aluminum vise jaws and unscrew with a strap wrench.

But this time it came apart by hand. The o-ring is rock hard. It's got 90 degree edges. Toast.

Disassembled. Pretty straightforward Crosman valve stuff.

There's a felt ring, a brass screen, steel washer, spring, piercing needle and the valve stem.

Had to crack the old o-ring to get it off.

You'd swear this is a plastic ring.

A couple new valve body seals next to the old one.

Actually had a new valve stem on hand. I think Bryan & Associates, Precision Pellet, JG Airguns, Mac1, Archer Airguns and several other places sell rebuild kits. Use the Google to track them down. The red stuff on the seal is Crosman Pellgun oil.

I'll try this o-ring. The valve is loosely threaded together. Gets tightened once it's inside the gas tube.

Pushed the valve into the tube from the front.

Used a transfer punch to align the threaded hole for the securing bolt.

Like so.

Tightened the rear of the valve in place.

Then snugged down the valve inside the tube.

Installed a bulk-fill cap. At this point, the entire gas tube is now sealed and can be pressure checked for leaks.

A small 3.5 oz tank with the B&A adapter.

Just a tiny bit of CO2 gas before reassembly.

Tapping the valve stem with a dowel rod will crack open the valve and vent CO2 through the transfer port. I'll leave it pressurized overnight.

More soon.

Thursday, March 10, 2011

Overhauling a Crosman 160 Part 1

I briefly mentioned this Crosman 160 last year, and even made a bulk-fill cap for it, but the other day, it started leaking from the valve stem.

Fair enough--it's at least 40 years old. Time for a full tear down and rebuild.

Just a few pics.

Started by removing the two screws holding the aperture sight.

Next, the safety has to be removed.

Rotated it until it pointed down. Or in this picture, up.

Then pushed it out from the opposite side.

Almost there...

Like so.

Used a 7/16" nutdriver to remove the stock fixing nut.

And the action pulls out of the stock.

Removed the two screws holding the trigger assembly to the gas tube.

And the end caps come right off.

Used a 3/32" allen wrench to loosen the setscrew that retains the bolt.

Same size wrench removed the setscrew holding the barrel.

With a small flat blade, the barrel band was loosened and slid forward.

Forgot to remove the front sight first.

Slid the barrel band off the barrel.

This is the "locator stud". I kinda hate this part. The stock retaining nut is ugly and sits right where I want to rest my offhand. I've shortened a couple on similar guns and made recessed fittings that sit flush with the underside of the gun stock. I'm leaving this gun as is. Keeping a vintage gun vintage for a change.

Had to first break it loose (with padded jaws in the bench vise) before I could remove it. The threading is slightly damaged at the stock nut end from a prior owner. I'll probably just make a new one.

The valve face needs to be loosened up in the gas tube next.

I have a piece of steel strip given to me by nefarious airgunner Volvo a couple years ago. He had just sold off his QB 78 and passed on to me his single most beloved of airgun tools. A silver Sharpie commemorated it's lineage.

Just used it to unscrew the front of the valve a couple turns.

Took out the valve securement screw. (if you take this out before breaking the front of the valve loose, the valve may just spin in the gas tube)

Hmmm. The barrel is stuck.

Nope. Didn't miss any fasteners. Looked at a schematic one more time.

Clamped the barrel in the vise (rubber covered jaws) and gave it some sheer brute force.

And the barrel pulled straight out.

Revealing the hidden forward breech screw.


And the breech pulls off.

Slid the bolt out of the breech.

It's much more substantial than the bolt on a modern day Crosman.

The hammer assembly is still in the gas tube.

Removed the pin and took out the spring guide and hammer spring.

Cocking pin and hammer came out.

This is their orientation inside the gas tube. A pic for my reference.

More soon.