GTA
Airguns by Make and Model => Crosman Airguns => Topic started by: Moke on August 07, 2024, 11:16:55 AM
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So, my Crosman Backpacker 2289 has developed an ism where the forearm pops open under normal pressure. It actually got me slightly in the junk the other day when I placed the rifle across my knees.
So, to protect certain areas, I have opted to use a velcro band that I capture the forearm with.
What causes this?
Fixes?
Note the velcro band around the barrel and valve tube in the image.
There is a dead rat in the image as well. If that is offensive, please don't open the image.
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What normally keeps it closed, a latch? a spring?
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I assume it is held in place by internal air pressure. There is no latch, spring, or overt method in its stock form.
But this first started happening a couple of years ago, and, I mounted some rare earth magnets within the forearm, and they contacted the air tube, and, held it with magnetic attraction. But, now, even that no longer works.
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Most folks have their 13xx set up so the piston just barely cams over and locks. For those with a flat topped piston that's adjustable, this is easy. Not sure what to do with a stock piston. Should be a way to adjust it. Might be a part that is worn or a hole that is ovalled due to use. (Pump linkage arm?) But the 13xx gurus should be able to help you.
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Moke,
After enough shots the 13xx or 2289 can start to have a floppy pump arm. I have had 2 so far that got to this point. My fix is to shim the pump cup using a 9" thread tape rolled into a string and placed between the piston and pump cup. I put 6 rounds, doing this fixes the floppy arm and also I get a small boost in FPS at 10 pumps
NVak
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Moke,
After enough shots the 13xx or 2289 can start to have a floppy pump arm. I have had 2 so far that got to this point. My fix is to shim the pump cup using a 9" thread tape rolled into a string and placed between the piston and pump cup. I put 6 rounds, doing this fixes the floppy arm and also I get a small boost in FPS at 10 pumps
NVak
+1 This! or what I did was cut a washer from a empty plastic milk jug to go under the pump cup.
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Worn pivot pin might cause this too. Cheap fix is the pump cup shim.
But do check for worn parts. It's less expensive in the long run to not let them go too far.
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A dented valve can also cause this (left in the pic). My solution is to machine the valve to install a hardened steel ring (right in the pic). You'll see that issue happening after a while using the gun. Another cause I've seen is a slightly collapsed plastic piston.
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many thanks all.
I'm still studying on this, and working up some questions.
If you were to choose a flat valve,... would it be an adjustable one, or, a permanent length?
I'm looking at both systems, and the non-adjustable is about 1/2 the cost. It can be made to be adjustable at a later time, if needed.
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If it was me (and it was a couple of times) I'd go with the adjustable one. Then you get a perfect fit for your gun with whatever wear you have and maximum compression. If you are going to do something, might as well just do it once. Just my humble opinion.
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A reasonable and adjustable solution for flat top piston and valve can be found at Mellon's website. Both together can be purchased for $30. On eBay I found some flat top sets for $140! Sure they are different, but I'd bet that the delrin piston and aluminum valve will work just fine.
He's a crusty guy, as you can tell by his comments on the website, but he continues to make stuff that works. https://mellonair.myfreesites.net/pistons-valves Be aware that he may take his time, but he always seems to come through. At least he has for me.
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I owe you a giant wet puppy lick.
many thanks!
yeah,.... those $140/$150 valves were putting me off.
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If you over pump the gun regularly you can expect more issues like this in the future... just sayin'.
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Never abused.
I've only ever taken it to 10 pumps, which I understand is the suggested working limit. But I've done that a thousand times or more.
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Moke,
After enough shots the 13xx or 2289 can start to have a floppy pump arm. I have had 2 so far that got to this point. My fix is to shim the pump cup using a 9" thread tape rolled into a string and placed between the piston and pump cup. I put 6 rounds, doing this fixes the floppy arm and also I get a small boost in FPS at 10 pumps
NVak
+1 This! or what I did was cut a washer from a empty plastic milk jug to go under the pump cup.
Alrighty,... still studying on this. Learning, learning, learning,...
So, this shim goes between the piston shaft, and the piston cup, in order to slightly lengthen the entire piston assembly?
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A reasonable and adjustable solution for flat top piston and valve can be found at Mellon's website. Both together can be purchased for $30. On eBay I found some flat top sets for $140! Sure they are different, but I'd bet that the delrin piston and aluminum valve will work just fine.
He's a crusty guy, as you can tell by his comments on the website, but he continues to make stuff that works. https://mellonair.myfreesites.net/pistons-valves Be aware that he may take his time, but he always seems to come through. At least he has for me.
I received and installed this flat valve, yesterday. Everything went really well, except for my bobbling of, and losing that tiny ball bearing for the safety.
But as far as the valve went,... It went perfectly. The rifle pumps up, and the forearm stays closed, even out to pump-level 15.
Yea! many thanks for the tip.
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A reasonable and adjustable solution for flat top piston and valve can be found at Mellon's website. Both together can be purchased for $30. On eBay I found some flat top sets for $140! Sure they are different, but I'd bet that the delrin piston and aluminum valve will work just fine.
He's a crusty guy, as you can tell by his comments on the website, but he continues to make stuff that works. https://mellonair.myfreesites.net/pistons-valves Be aware that he may take his time, but he always seems to come through. At least he has for me.
I received and installed this flat valve, yesterday. Everything went really well, except for my bobbling of, and losing that tiny ball bearing for the safety.
But as far as the valve went,... It went perfectly. The rifle pumps up, and the forearm stays closed, even out to pump-level 15.
Yea! many thanks for the tip.
Glad I could help. Now you need to find some of those ball bearings! Not positive, might be 3/32" or so, but do a search to be sure. You can buy a whole bag of them for cheap money.
Edit: I did the search and they are 3/32".
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Another big wet wiggly puppy lick for you for the bearing size.
really,... thanks again.
I also bought this rolled spring pin replacement from him, since I was diving in.
https://mellonair.myfreesites.net/solid-pins
It is a well thought out screw, covered in an affixed tool steel sleeve of the same diameter as the OE pin. It also has a second steel sleeve that is intended to reline the original pivot point hole with a fresh sleeve. Mine: had worn to an oval, which is likely where I ran into the pop open ism.
The secondary free rotating sleeve on the solid pin replacement is a great feature.
What I can't figure out is the standalone silver washer/disc thing that is sold with the kit. So it got labeled and stowed for now.
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Another big wet wiggly puppy lick for you for the bearing size.
really,... thanks again.
I also bought this rolled spring pin replacement from him, since I was diving in.
https://mellonair.myfreesites.net/solid-pins
It is a well thought out screw, covered in an affixed tool steel sleeve of the same diameter as the OE pin. It also has a second steel sleeve that is intended to reline the original pivot point hole with a fresh sleeve. Mine: had worn to an oval, which is likely where I ran into the pop open ism.
The secondary free rotating sleeve on the solid pin replacement is a great feature.
What I can't figure out is the standalone silver washer/disc thing that is sold with the kit. So it got labeled and stowed for now.
Is that washer a spacer/bushing that goes into the pivot point on the pump arm where the roll pin goes through?
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Another big wet wiggly puppy lick for you for the bearing size.
really,... thanks again.
I also bought this rolled spring pin replacement from him, since I was diving in.
https://mellonair.myfreesites.net/solid-pins
It is a well thought out screw, covered in an affixed tool steel sleeve of the same diameter as the OE pin. It also has a second steel sleeve that is intended to reline the original pivot point hole with a fresh sleeve. Mine: had worn to an oval, which is likely where I ran into the pop open ism.
The secondary free rotating sleeve on the solid pin replacement is a great feature.
What I can't figure out is the standalone silver washer/disc thing that is sold with the kit. So it got labeled and stowed for now.
Is that washer a spacer/bushing that goes into the pivot point on the pump arm where the roll pin goes through?
Yes, it goes between the two “tines” to prevent that “twisty” movement when pumping.
This one’s just a flat washer but works the same.
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You can use 2 washers depending on the thickness, then just lap to fit.
Got the idea from Mudduck of the CAPOF 👍
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That pivot point was chewed up pretty bad, to an oval shape. So, i did not recognize that the hole is just two halves of punch press holes that perfectly aligned to each other to create a thru-hole.
So, I inserted a screw driver blade, and tried to move that "hole" as I thought it might just be an insert. That made the hole even more ragged before I realized that it was two aligned punched sections pressing together.
So I fired up my angle grinder and cut-off blade, and I reached between the two "tangs" and cutaway the punched thru-hole, and ground off the now two nipples. I ground them back to flush, and inserted the silver disc to a perfect fit.
I also used a thin nylon flat washer between the wall of the barrel band, and the steel pump mechanism, to shore up that side to side slop thing.
The barrel band got a new stainless allen cap screw and nylon lock nut, rather than that construction screw like thing that was stock.
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thanks again, all!
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I try not to tell people what they should and should not do with their guns but this is one of the results of over pumping these guns. Sure, they will eventually wear under normal use but over pumping drastically speeds up the failure.
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This is just a result of thousands and thousands of pumps that I never took it beyond 10 pumps in a single shot. But I did those ten pumps, many, many thousands of times.
I did recently suggest going to 15 pumps after installing the flat valve, but, that was just in testing the forearm steadiness. And when I shot it, my wife said that it was far louder, which is something that I do not desire.
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This is just a result of thousands and thousands of pumps that I never took it beyond 10 pumps in a single shot. But I did those ten pumps, many, many thousands of times.
I did recently suggest going to 15 pumps after installing the flat valve, but, that was just in testing the forearm steadiness. And when I shot it, my wife said that it was far louder, which is something that I do not desire.
Mike, my reply was very general. In no way was I suggesting or accusing you of over pumping. But yeah, as with most things mechanical, they even wear with normal use.
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This is just a result of thousands and thousands of pumps that I never took it beyond 10 pumps in a single shot. But I did those ten pumps, many, many thousands of times.
I did recently suggest going to 15 pumps after installing the flat valve, but, that was just in testing the forearm steadiness. And when I shot it, my wife said that it was far louder, which is something that I do not desire.
You could also reinforce your valve with a set screw on top, especially now that you have a flat top (I’ll look for that thread).
I copied Wyoman’s mod years ago with my Crosman pistols.
Here’s another reinforcement but this one is to the metal barrel band:
https://www.gatewaytoairguns.org/GTA/index.php?topic=139287.0
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This is just a result of thousands and thousands of pumps that I never took it beyond 10 pumps in a single shot. But I did those ten pumps, many, many thousands of times.
I did recently suggest going to 15 pumps after installing the flat valve, but, that was just in testing the forearm steadiness. And when I shot it, my wife said that it was far louder, which is something that I do not desire.
You could also reinforce your valve with a set screw on top, especially now that you have a flat top (I’ll look for that thread).
I copied Wyoman’s mod years ago with my Crosman pistols.
Here’s another reinforcement but this one is to the metal barrel band:
https://www.gatewaytoairguns.org/GTA/index.php?topic=139287.0
13xx valve pinning that also works on 22xx C02 guns:
https://www.gatewaytoairguns.org/GTA/index.php?topic=185793.0
Wyoman’s a genius and a great builder, yes sir 👍
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Would be nice if the area in question were reinforced (somehow). The fact that the pivot hole wore out means it was under designed. Or the manual didn't give the correct number of maximum pumps. It's obvious that the tougher the pumping is, the more it pushes on that hole. So the max pumps specification should have been reduced - at least in the owner's manual. Now most of us won't pay attention, but, at least we were warned. If that folded sheet metal was 10-15% thicker, I'd bet it would last longer. Or maybe one could install a larger diameter bushing to spread out the load below deformation.
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Or replace it with a solid billet arm. ;)
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Or replace it with a solid billet arm. ;)
I did see one years ago but could not recall if it was for the 13xx or the 2100 🤔
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I'm sure a few of our talented members could make them.
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Can't claim any machining talent, but that would be the sort of thing that I'd try for the heck of it. I don't have a stock pile of LEGO parts, and who knows how long they will remain available. Might have to try some time. I've certainly had mine apart enough times.
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I feel very lucky to have been dropped into the timeline precisely at the time of the Crosman "lego" era. I fear it's time is coming to an end.
It may be a wise move to do some research and hoard up on what may be still available if the plan is to continue enjoying them for years to come.
Yeah, there were many sold and there are a butt load of them out there but the parts that fail/wear are common and it won't be much joy with buying used ones to repair your broken ones.
Aftermarket will dictate the longevity.
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So, yesterday, after looking at the grip of my 2289, and the liberal application of electrical tape to the grip to steady it as a real handle, I finally decided to screw mount the grip to the metal pistol handle frame.
I love how Crosman put the crosshairs at where you needed to drill, and that they pre-threaded the thru-hole to 6-32. I even confirmed it with electrical switch plate screws, perfect.
So, I run off to the hardware store, and buy the perfect screws, and,...
I hand tightened them to a point of needing an allen wrench to finish, and guess what?
Immediately on tightening, the pot metal of the frame just crumbled and fractured away. And not enough thread was left to get a single side seated.
This meant drilling the whole hole out, and, rethinking how to get a pair of screws into that space,.... Corby bolts! (screws that have both *nut and bolt looking like male screws)
Do you think that I could find a Corby bolt in northern San Diego, or even southern Riverside counties? nope!
I found something similar, and it will work until I can track down a real Corby bolt.
* How do you tell a nut from a bolt at the hardware store?
Men are bolts, and, women are nuts
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So, yesterday, after looking at the grip of my 2289, and the liberal application of electrical tape to the grip to steady it as a real handle, I finally decided to screw mount the grip to the metal pistol handle frame.
I love how Crosman put the crosshairs at where you needed to drill, and that they pre-threaded the thru-hole to 6-32. I even confirmed it with electrical switch plate screws, perfect.
So, I run off to the hardware store, and buy the perfect screws, and,...
I hand tightened them to a point of needing an allen wrench to finish, and guess what?
Immediately on tightening, the pot metal of the frame just crumbled and fractured away. And not enough thread was left to get a single side seated.
This meant drilling the whole hole out, and, rethinking how to get a pair of screws into that space,.... Corby bolts! (screws that have both *nut and bolt looking like male screws)
Do you think that I could find a Corby bolt in northern San Diego, or even southern Riverside counties? nope!
I found something similar, and it will work until I can track down a real Corby bolt.
* How do you tell a nut from a bolt at the hardware store?
Men are bolts, and, women are nuts
Next time, I recommend using a tap to thread the holes.
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The metal frame hole was already threaded at the factory. I tried a wall plate screw (matching 6-32 thread), and it cleared smoothly and cleanly all the way through. I got the fracturing of the cast pot metal threaded hole on the first and slightest compression/hesitation while tightening; emphasis: slightest.
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I ordered a new forearm pump links mechanism yesterday.
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I like the way Vernon Austin attaches his laminate/wood pump arms onto the linkage: he drills and taps the bottom, so there are no side holes. It’s actually more solid. He also embeds dampers to make it very quiet.
I haven’t used my pumpers in a long time though 🤔