Some work done, but now the 1377 is much harder to pump

[1377x]

no the pin isnt supposed to rotaed it would fall out if it did
im thinking maybe when you pounded the pin into your tube you bent the tube in i mean to the distance between the two holw is closer now
pull the pin out and the barrel band, see if the piston come out freely.if it does not tand you have to exert more force than normal to get the piston out you are going to have to spread the tube apart its easy but takes finess.you only spread it apart enough to remove the piston with very little force

[Tater]

no the pin isnt supposed to rotaed it would fall out if it did
im thinking maybe when you pounded the pin into your tube you bent the tube in i mean to the distance between the two holw is closer now
pull the pin out and the barrel band, see if the piston come out freely.if it does not tand you have to exert more force than normal to get the piston out you are going to have to spread the tube apart its easy but takes finess.you only spread it apart enough to remove the piston with very little force

When I open the forearm to pump it it opens up very smoothly. If the tube is out of round wouldn't it be tighter going in both directions? I don't doubt you, just trying to learn.

[PC77]

I am thinking a little Rem oil got to the o-rings and tighten them up a little.
pc

[Tater]

I am thinking a little Rem oil got to the o-rings and tighten them up a little.
pc

It's been a couple weeks since I did it but your probably right. Would that just make it seal better and better compression or should it be cleaned off of the o-rings (Pellgunoil)? I always thought they needed lube to not dry out. 

[WyoMan]

Tater, I thought you had OEM piston, pump cup problem only thing I can think of that makes it hard in
compression but not in intake, unless it's only hard on the high number of pumps or linkage is severely
misaligned that happens on compression (push) but not on pull

[1377x]

Tater, I thought you had OEM piston, pump cup problem only thing I can think of that makes it hard in
compression but not in intake, unless it's only hard on the high number of pumps or linkage is severely
misaligned that happens on compression (push) but not on pull

how does that happen?
i had a similar problem like i said my check valve wasnt opening valve couldnt get any air,pressure built up in the tube and had no where to go,thats not the case here his gun fires after pumping

[plasticclassic]

If you lube the OEM piston a lot, just that will make it harder to pump IMO

How does it pump if you take out your solid pin and temporarily use as a pin the drill bit end you used to enlarge the hole with, or a steel punch of the same diameter as the drill bit?

[Tater]

If you lube the OEM piston a lot, just that will make it harder to pump IMO

How does it pump if you take out your solid pin and temporarily use as a pin the drill bit end you used to enlarge the hole with, or a steel punch of the same diameter as the drill bit?

I could try that tonight, but I'm at work now.

[WyoMan]

how does that happen?

Not sure Ed - this seems to have everyone stumped
The pump cup is the only thing (or should be) in contact with the inside tube
If all pivots on linkage are free than I don't know what else could bind up
I think you give good advise - don't pump anymore and and see if piston will come out

[Tater]

For what it's worth, I did compare it to a borrowed 1377 last night. The borrowed one pumps MUCH easier but it does have a leaky seal. I wish I compare it to a stock 1377 or let someone else try mine for a second opinion. Picked up a set of pin punches last week at HF so if I do have to get that pin out to test the piston it will be easier. Not looking forward to that though because it is in there really tight.

[WyoMan]

Not looking forward to that though because it is in there really tight.

I know what you mean - I hated to have to do that when I had roll pins
One last question: Is it only hard to pump at the very bottom of the stroke where the piston contacts the valve?
If so, there may be nothing wrong - you may have moved the piston a little closer to the valve when you modified the pivot hole.
I know it's a long shot. If you decide to punch the pin out, it may be best to take it out in opposite direction of how it went in.

[Tater]

I know what you mean - I hated to have to do that when I had roll pins
One last question: Is it only hard to pump at the very bottom of the stroke where the piston contacts the valve?
If so, there may be nothing wrong - you may have moved the piston a little closer to the valve when you modified the pivot hole.
I know it's a long shot. If you decide to punch the pin out, it may be best to take it out in opposite direction of how it went in.

It's actually hard to pump most of the way to the bottom of the stroke but it gets worse the further down it goes. I can't think the piston moved to much at all. I actually hand-turned the drill bit and it was almost the right size already so minimal material was removed.

[WyoMan]

10-4, Sorry I couldn't better....

[breakfastchef]

Man up, Tater. Strip the gun down, do a visual check and reassemble. Sometimes the process corrects the problem, besides, this is a right of passage to the next level. Pivot pin sounds fine since the arm swings loosely when open. The linkage pin connecting the piston is probably ok since you can actually pump the gun (with effort) and do not hear any metal on metal scratching.

Couple of other thoughts related to the piston and valve.

What o-ring do you have on the piston? OEM? Replacement? Make sure the piston cup has not come loose.

Open the valve and clean th einternals. Check the spring for bends or damage. It may be possible an internal valve problem is making it difficult for the check valve to open smoothly. Make sure there are no obstructions in the inlet to the valve that could be blocking airflow. Dirt and grasy build up can certainly affect performance.

[Tater]

The oring and piston are OE M.  I havent ever even seen a valve or spring so I need to read up on those.