GTA
Airguns by Make and Model => Crosman Airguns => Topic started by: Matt15 on December 19, 2014, 07:01:45 PM
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Hello. I am working on my crosman 2100 and can not get it to dump more that 8 pumps. I used the stock spring and it would only dump 4. I got a disco spring and that dumped 8 with a shotgun primmer as preload. I have sanded the inside of the tube where the hammer slides and I have polished the hammer. I tried .25 pellets smashed in the back and more weight it dumped less. I am at my wits end so can you guys give me some suggestions. Thanks
Matt
P.S. on eight pumps it does 700 fps with 7.4 grain pellets
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Hello. I am working on my crosman 2100 and can not get it to dump more that 8 pumps. I used the stock spring and it would only dump 4. I got a disco spring and that dumped 8 with a shotgun primmer as preload. I have sanded the inside of the tube where the hammer slides and I have polished the hammer. I tried .25 pellets smashed in the back and more weight it dumped less. I am at my wits end so can you guys give me some suggestions. Thanks
Matt
P.S. on eight pumps it does 700 fps with 7.4 grain pellets
what have you done to the exhaust side of the valve and exhaust poppet... did you use a lighter spring in the valve...
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Hello. I am working on my crosman 2100 and can not get it to dump more that 8 pumps. I used the stock spring and it would only dump 4. I got a disco spring and that dumped 8 with a shotgun primmer as preload. I have sanded the inside of the tube where the hammer slides and I have polished the hammer. I tried .25 pellets smashed in the back and more weight it dumped less. I am at my wits end so can you guys give me some suggestions. Thanks
Matt
P.S. on eight pumps it does 700 fps with 7.4 grain pellets
what have you done to the exhaust side of the valve and exhaust poppet... did you use a lighter spring in the valve...
Yes I have a lighter spring in the valve. I have to cock it before I pump it.
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I would definitely look at the valve as the cause. Have you done any kind of valve mods?
It sounds like when I accidentally made a valve spring guide to long and the valve would barely open (done to reduce valve volume), though that was on a 2289.
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I would definitely look at the valve as the cause. Have you done any kind of valve mods?
It sounds like when I accidentally made a valve spring guide to long and the valve would barely open (done to reduce valve volume), though that was on a 2289.
My 2100's original valve I tore up.(Did not no what I was doing.) >:( So I got a 13xx valve and modded the back to work in a 2100 and put a 2100 valve top on it. I out the exhast hole so a 2100 t port would work on it. I will have to open the valve and take a look.
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any mods to the poppets?
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I would definitely look at the valve as the cause. Have you done any kind of valve mods?
It sounds like when I accidentally made a valve spring guide to long and the valve would barely open (done to reduce valve volume), though that was on a 2289.
My 2100's original valve I tore up.(Did not no what I was doing.) >:( So I got a 13xx valve and modded the back to work in a 2100 and put a 2100 valve top on it. I out the exhast hole so a 2100 t port would work on it. I will have to open the valve and take a look.
If you are using the 13xx valve stem that could be the trouble, just a thought.
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well I know it is a flat top valve and he is building pressure very well and it can be porting or he might have reduced the diameter of the seat portion of exhaust poppet.
it could probably use turning down the stem of the poppet, I think it could use being opened to .140 (stock is about .125?) thru the barrel support/transfer port. also the inside corner of the exhaust throat needs a slight rounding.
ok you are now getting your pump to build pressure in the 80-90% eff. range instead of 60-80%
I do not know your altitude so 14.3 psi for atmosphere...
and about what I think you have for valve volume... (flat tops shine with smaller valves)
Pump Tube Diameter Pump Tube Stroke Reservoir Volume swept volume
0.62 5 0.07 1.50877
PSI Per Stroke
308
number of strokes
8
PSI @ 60% Efficiency PSI @ 70% Efficiency PSI @ 80% Efficiency
1479.456754 1726.03288 1972.609006
PSI @ 65% Efficiency PSI @ 75% Efficiency PSI @ 85% Efficiency
1602.744817 1849.320943 2095.897069
there is a point but back in a few...
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Matt when you polished the tube and hammer, what did you relube with? The only lube that should be used on the hammer is oil, no grease. Also check the valve stem, if it is bent it will cause the valve to open slowly.
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I would definitely look at the valve as the cause. Have you done any kind of valve mods?
It sounds like when I accidentally made a valve spring guide to long and the valve would barely open (done to reduce valve volume), though that was on a 2289.
My 2100's original valve I tore up.(Did not no what I was doing.) >:( So I got a 13xx valve and modded the back to work in a 2100 and put a 2100 valve top on it. I out the exhast hole so a 2100 t port would work on it. I will have to open the valve and take a look.
If you are using the 13xx valve stem that could be the trouble, just a thought.
I forgot to mention that I did make the stem shorter.
any mods to the poppets?
Not the exhast but the intake i made shorter. I think I know what is wrong. ::) I shortened the intake poppet to much and supper glued a small nut to the back of the intake because the valve spring was to short. When I opened the valve the nut was moving freely in the valve(Stupid me). I need to get a longer valve spring.
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Matt when you polished the tube and hammer, what did you relube with? The only lube that should be used on the hammer is oil, no grease. Also check the valve stem, if it is bent it will cause the valve to open slowly.
Hi Bart I posted the same time as you ;D Yes I used oil to lube it. Valve is not bent so see my explaination above. :D
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any mods to the poppets?
Not the exhast but the intake i made shorter. I think I know what is wrong. ::) I shortened the intake poppet to much and supper glued a small nut to the back of the intake because the valve spring was to short. When I opened the valve the nut was moving freely in the valve(Stupid me). I need to get a longer valve spring.
That would do it. I wish you luck.
You may be able to stretch the spring you are using enough to do the job, it will be rather weak and likely require cocking the gun to pump though it should work.
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any mods to the poppets?
Not the exhast but the intake i made shorter. I think I know what is wrong. ::) I shortened the intake poppet to much and supper glued a small nut to the back of the intake because the valve spring was to short. When I opened the valve the nut was moving freely in the valve(Stupid me). I need to get a longer valve spring.
That would do it. I wish you luck.
You may be able to stretch the spring you are using enough to do the job, it will be rather weak and likely require cocking the gun to pump though it should work.
Thanks. I will try stretching it. I do have to cock it before I pump it right now.
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In order to get every last bit of volume out of my extended nose 2100 valve I modded the exhaust poppet.
Reducing size and rounding the end let it create less closing force felt...
I see you changed a nut well that takes up space and so getting your valve volume right?? How big a nut ;)
so anyways at 1800 psi it reduced closing force(therefore cracking force needed) on the poppet by ~54 lbs
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The good news is you got the pump going very well and you just need to get it to dump. It may flow well enough even with stock porting...
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In order to get every last bit of volume out of my extended nose 2100 valve I modded the exhaust poppet.
Reducing size and rounding the end let it create less closing force felt...
I see you changed a nut well that takes up space and so getting your valve volume right?? How big a nut ;)
so anyways at 1800 psi it reduced closing force(therefore cracking force needed) on the poppet by ~54 lbs
I cut the intake seal to short and my spring was not long enough. So I glued a nut that was same diameter as the spring and about 1/8 inch thick. Last night I did stretch the spring and it worked. I have yet to test it though.
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I am interested to read the results :) .
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I am interested to read the results :) .
Well I rounded the exhaust poppet like K.O. did. I stretched the spring in the valve and it holds air. However it does not want to dump the air. In streching the spring it made the spring stronger so it dumps less. I need to get a lighter spring and then I will be good to go. Right now the hammer just barely holds it open when uncocked.
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Update. I got my 2100 to dump 10 pumps for about 760 fps with 7.4 grain pellets. I can not get it to dump more pumps. I am going to leave it like this until after Christmas. However I think I know why it will not dump more than 10 pumps. I noticed on the valve stem the valve seat has sunk about 1/8 inch deep in to the stem seal and it makes it hard to dump. 8) So in January I will call crosman and order a stem seal and a few other things I need.