Achieving 100% Air Seal in Your Gear Box

Discussion in 'Gun Building, Modifications & Repairs' started by Griffin, Mar 19, 2011.

  1. Griffin

    Griffin Active Member Supporting Member

    4,313
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    Achieving 100% Air Seal in Your Gear Box




    **Some Guns Already Have 100% Compression In Stock Form once you have lubed it (or even if you don't lube it). Please try your guns compression before doing the following** (View "Checking The Compression" below)






    Piston Head
    Put a new o-ring on your piston. Generally a #14 o-ring from a hardware store will do fine. Sometimes it will be to big/to small. To get a even better air seal, get a old gear box cylinder, stretch the o-ring around it, get a lighter, and slowly turn the cylinder while holding the lighter under the o-ring. **Doing it to much will cause the o-ring to weaken/break/stretch to much. Be sure to not do it for to long**. The part about heating the o-ring is not always 100% necessary, but it is good to follow.

    After you have installed a new o-ring onto your piston, be sure to put a small dab of lube and rub it around the o-ring. This will ensure a good seal. Do not use silicone spray (as it will wear off quickly) or lube with petroleum as it will wear down the o-ring. I would recommend using most kinds of silicone grease. More does not mean better. Use only a tiny bit. To much may cause bad performance. To little will also cause bad performance.


    You may also want to port the piston if it is not already.

    To port the piston head, drill more holes/bigger holes in the holes that are already in the piston head. Just make sure not to go so deep it goes through the second part of the piston head. This is not necessary and you may be able to get a full air seal without it. If you want, try it without this first. I generally do not port my piston head and I get a full air seal.









    Cylinder
    Apply a very THIN amount of grease inside the cylinder. You don't want it to be bone dry, but you don't want there to be so much grease it plugs up the cylinder head nozzle.










    Cylinder Head
    Put teflon tape around the o-rings on the cylinder head for better seal. Not always necessary. Most cylinder heads on guns I have worked on do not need this step done.

    Put a small amount of grease around the o-rings on the cylinder head. Not to much.








    Checking The Compression
    Once you have completed everything above, install the cylinder head and piston into the cylinder and install it into the gear box (but do not close the gear box and leave out any other components such as the gears). Put your finger on the end of the cylinder head (do not put on the air nozzle yet). After you have done this, keeping your finger on the cylinder head nozzle, push the piston forward. Once the piston has gone past the ports in your cylinder (assuming there are some), you should not be able to push the piston forward at all. If you can, you might have messed up in the above steps, bad quality internals, or you heated the o-ring to much.







    Air Nozzle
    Do the above step again except for put the air nozzle on with the tappet plate and tappet plate spring attached inside the gear box.

    If you can push the piston forward after the ports in your cylinder, you have bad compression (obviously). Try placing a small o-ring (sorry, don't know the size) at the bottom of the air nozzle and gluing it on (make sure to not block the air flow) then put it onto the cylinder head. That should help. if you still have a leak, you either did not use a small enough o-ring or you have a crappy air nozzle. Try buying a new one that has a built in o-ring inside of it, aswell put a o-ring on the bottom of the new one as it will help. No need to lube the air nozzle.





    Wrote this all at one time so it might have some errors. If there is anything to make it better, something I wrote wrong, or if you have any questions, please suggest it/ask it.


    Thanks.
     
    Last edited: Mar 24, 2011
    Belgrim and Airsup like this.
  2. Uller

    Uller Well-Known Member

    2,197
    297
    Topeka
    To get an airseal between my cylinderhead and cylinder I use permatex anaerobic gasket maker.A very thin smear on the cylinder head,and where the cylinderhead meets the cylinder is all thats needed.It bonds in the abscence of oxygen,and the parts are still easily removed.Superior to teflon tape,and works well on buckings without having to use dental floss.
     
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  3. alex

    alex New Member

    4,794
    7
    Atlanta
    the air nozzle test should be done with the tappet plate and spring installed. the nozzle should be in the extended position to test for leaks. you can get false airseal test if the nozzle is butt up against the cylinder head.

    if there is a leak, you will hear the hissing sound at the nozzle.

    one piece hopups (with barrel) can be tested while the nozzle is in the extended position. just push the hopup/barrel and plug the open end with your finger then push the piston in. it will have more bounce than usual but if there is any leakage, you will hear it. put your ear next to the hopup to hear any leaks.
     
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  4. alex

    alex New Member

    4,794
    7
    Atlanta
    i'm gonna try that stuff... thanks
     
  5. Griffin

    Griffin Active Member Supporting Member

    4,313
    5
    Thanks.

    Added that.
     
  6. wiseman

    wiseman Active Member

    1,474
    0
    I use high temp cylinder gasket maker mechanics use in car engines....it's cheap and really works well!:D:D:D
     
  7. theonlyBuster

    theonlyBuster Active Member Lifetime Supporter

    14,153
    14
    S. Florida
    Nice explanations.
    My only 2 complaints, well more like a pet peeve and a recommendation...
    Pet Peeve: There's not literal thing as 100%, it's impossible. 99% is more plausible.
    Recommendation: You should include a quick tutorial about checking the compression. You stated it in the very beginning to check for compression, but didn't really state how. Either add how, or a link to a page/thread explaining how.
     
  8. Griffin

    Griffin Active Member Supporting Member

    4,313
    5
    I did state how lower below. Anyways, updated.
     
  9. chaosnemesis

    chaosnemesis New Member

    996
    3
    Yep, I use something called blue gasket maker. Incidentally, it's the same stuff I use to fix leaky gas magazines.
     
  10. 733t samsqatch

    733t samsqatch New Member

    1,453
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    Madison
    How come nothing was said about a piston head? Im sorta new to the GB thing
     
  11. Griffin

    Griffin Active Member Supporting Member

    4,313
    5
    When I said the piston, I meant the piston/piston head. Updated.
     
  12. alex

    alex New Member

    4,794
    7
    Atlanta
    it was included in the piston section. but we sometimes relate the piston head with the piston. technically, you're right, it should have it's own section. they have different type porting, base screw (metal vs plastic), shock absorbency (nylon, POM, aluminum, plastic). for the plastic/nylon, i usually make sure the burs on the ports are filed down smooth to allow the o-ring to seal better. i don't necessarily drill out the ports larger, but some re-drill the ports if they use sorbo pads on them. this doesn't really affect airseal, but a bad sorbo job will.
     
  13. grim

    grim New Member

    70
    0
    lancaster
    So my problem came up in the nozzle step. Logic would say replace it. Which once my bore up kit shows up ill try. My concern is will that work with a kwa. I have noticed the air nozzle looks much different that that of other guns. If the nozzle is incompatable would using a different hop up do the trick
     
  14. klinefrog

    klinefrog New Member

    2,013
    1
    Costa Mesa
    both the air nozzle and the hop up unit on KWAs are proprietary so they will not work with any other nozzles or hop up units
     
  15. grim

    grim New Member

    70
    0
    lancaster
    but if they are both swapped?
     
  16. klinefrog

    klinefrog New Member

    2,013
    1
    Costa Mesa
    i doubt that it will work since both the KWA nozzle and hop unit were designed to work together...KWAs do not like being messed with besides the barrel and even then you get very little performance difference...you can try it and see if you want
     
  17. grim

    grim New Member

    70
    0
    lancaster
    So you think even if im using aftetmarket nozzle and hop up the performance would suffer?
     
  18. klinefrog

    klinefrog New Member

    2,013
    1
    Costa Mesa
    the hop up will not suffer because the airnozzle has no role with the bucking and the nub except for airsealing which you may have problems if you dont use KWA nozzles
     
    REAPER556 likes this.
  19. grim

    grim New Member

    70
    0
    lancaster
    I asking about the airseal. If i use a aftermarket hop up when i switch the air nozzle out will the airseal be alright. Cuz my compression test showed my air nozzle leaks at the cylinder head. Hopefully the one coming with my bore up kit will perform better
     
  20. deathmechanic

    deathmechanic Active Member

    4,055
    17
    Davis
    As Kline has stated KWA uses proprietary hopups and air nozzles. If you change these out you will run into more issues. Call KWAs technical support and order a new air nozzle and hopup if needed.