How to improve compression in the cylinder?

[Icepick]

How do you improve compression in the cylinder? I am currently using a spare piston, piston-head, and cylinder to try these different methods... The first method I'm trying is using teflon-tape under the O-ring on the piston head, and It seems to make it air tight, but a lot stiffer and harder to move the piston assembly back and forth. (Even with lube.)

[Cap n pickles]

I would not use it on the Piston head, but on the Cylinder only.

Take out the piston O ring, go to a hardware store and find the O ring that is the same size.#16 i believe, It will be just slightly bigger, and give better compression.

[Freespace535]

The usual size is a #14 o-ring. I use them all the time, they definitely help compression. One trick I read about is to stretch it out onto a spare cylinder and heat it with a low intensity flame, like a lighter. Google up "DMR Holy Grail" for the details.

[Regular Guy]

Replace the O-ring. I do not like the teflon DIY because it will not last in the long run, you may have to open the gearbox to wrap another strip of teflon on the piston head if you notice a significant loss on FPS.

[Nec]

It seems you know how to check for good compression already, but incase you are doing it wrong lets start from square one.

Plug the cylinder head with your finger and running the piston up and down in a somewhat fast motion you should get firm pressure resisting your push in.



The most common place for leaks while doing this compression check is the piston head O-ring, replace with a #14 O-ring available at Lowes or any other well stocked hardware store. If you have already replaced the piston head O-ring and still getting bad compression you may want to do the cylinder Teflon mod, by wrapping Teflon tape (AKA plumber tape) around the cylinder head’s O-ring (sorry no pictures). Although a better alternative would be to either try a another cylinder or buy a new cylinder O-ring, IIRC it is a #19 O-ring available, you guessed it, at any well stocked hardware store


Next take the air-nozzle and place it on the cylinder head and clip on the tappet plate so that it looks like this:


Why do this? Because when the gearbox is put together and the piston is about to go forward the air nozzle is pushed although way out so that it can make good compression with the "lips" of the hop-up bucking. Running the piston up and down in a somewhat fast motion you should get firm pressure resisting your push in.

If you find a leak with the air nozzle the best thing to do is to find ether a tighter fitting air nozzle such as a TM or one with an O-ring inside.


If you don’t find a leak here but when you put the gun back together you get really bad FPS, trying switch out the air nozzle with a longer one. When I saw replace it with a longer one, I’m not talking about one that’s twice as long I’m talking about one that is microscopically longer such longer by .1mm - .2mm longer.
Lets say your stock air nozzle is 21.12mm long.



Try replacing it with a 21.22mm air nozzle.


Here are some other places to check for compression.

[Icepick]

WOW!

Extremely helpful! I am for sure using this guide, thanks.

A few quick questions... So I already have a TM air nozzle, should I replace it with one that has an O-ring? And I want to replace a plastic cylinder head with a metal one, is that necessary? (My plastic head is designed to fit an AK air nozzle, the metal one is designed to fit an AUG air nozzle, if the air nozzle can fit over the metal head it is good to use, right?)

[Nec]

WOW!

Extremely helpful! I am for sure using this guide, thanks.

A few quick questions... So I already have a TM air nozzle, should I replace it with one that has an O-ring? And I want to replace a plastic cylinder head with a metal one, is that necessary? (My plastic head is designed to fit an AK air nozzle, the metal one is designed to fit an AUG air nozzle, if the air nozzle can fit over the metal head it is good to use, right?)

Use which ever air nozzle and cylinder head combo that works the best. The cylinder head doesn't necessarily have to be metal, although I've noticed a change in the sound of the gun when using metal cylinder heads, for better or for worst.

[Icepick]

Is the piston movement supposed to be a lot more stiff if it is completely sealed in the cylinder? I am worried about a large drop in ROF due to this, but I have greased up the piston head and have it sitting in the cylinder, and it has seemed to improve.

*Will be adding on to this post if there are more questions*

EDIT: Well how do I make a compete seal, and have it move fluently? I may be making a big deal out of the difference, but I just don't know. Should I drop it in the gun and try it?

[pseudoanimosity]

The piston movement should be smooth, you should only have resistance if you move the piston fast enough to inflate your o-ring on the piston head

[Icepick]

I checked the compression on the TM cylinder, cylinder head, and air nozzle and it was all perfect. Only thing that lacked a little bit was the piston head. (O-ring didn't make a complete, 100% seal.) But this is all it took over the China piston and piston head to make this thing shoot twice as well... I also did a complete re-greasing of the gearbox. And this is really an obvious reason why I always say to do this. These results are very impressive, and it didn't even cost me a penny! I highly suggest working on the compression using the guide shown, and cleaning/re-greasing the gearbox as a first upgrade.

TL;DR

Compression and re-greasing makes the AEG better. (Should be known by most.)

[Nec]

I checked the compression on the TM cylinder, cylinder head, and air nozzle and it was all perfect. Only thing that lacked a little bit was the piston head. (O-ring didn't make a complete, 100% seal.) But this is all it took over the China piston and piston head to make this thing shoot twice as well... I also did a complete re-greasing of the gearbox. And this is really an obvious reason why I always say to do this. These results are very impressive, and it didn't even cost me a penny! I highly suggest working on the compression using the guide shown, and cleaning/re-greasing the gearbox as a first upgrade.

TL;DR

Compression and re-greasing makes the AEG better. (Should be known by most.)

You don't believe how many people I run into who don't have a clue about proper maintenance.

[Black Fox]

Icepick

Some additional tips can be found here.
http://airsoftpacific.com/viewtopic.php?t=30907