How do you sort air leaks?
 

I definitely have airleak..... just don't know where?! How do you know if it's from the hop-up, nozzle, cylinder head, or the piston o-ring?!?

I've checked the whole cylinder assembly.. including the nozzle, the piston head, and the cylinder head... i tested it by pushing the piston and blocking the nozzle (erected).. it seems that no air could escape.. but things could be different during the actual cycle. Especially with stiff springs like SP160. Unseen leaks can be a major leak when fully compressed.
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don't push the air nozzle against the cylinder head when you test for compression, and the piston should move forward very slowly. It should leak a little bit but not much at all, if it does then you need a new or different brand of air nozzle.
Try reinstalling your hopup rubber, make sure you use silicone lube on the OUTSIDE of the hopup rubber to make sure it doesnt catch or stick to anything while it's sliding into the hopup chamber :)

Take the whole gun and dip it in a tank full of water or Jello. Watch for rising bubbles. JK man!! I had too.

Sorry

Tank full of jello? gimme some!!!!


But for your air leak problem. open up the gear box, replace the parts.

Start by re-greasing your piston head, if thats not it, replace your air nozzle.

NEVER GREASE A PISTON HEAD.

It'll fuck up the expansion and contraction of the Oring.

Really, that's news to me. Interesting though, will have to try it at some point.

One tip is to use oil or lube and a small screwdriver, get it under the rubber O-ring, and gently stretch the O-ring by making circles around the pistonhead a dozen or so times. According to Illusion this is the way to condition the pistonhead O-ring on a Systema Silent Pistonhead, but since it'd a ported pistonhead anyways, it should be done on all piston head O-rings.

From my understanding, if too much grease gets into the port holes it'll effect it in a very negitive way.

From my understanding, those port holes are there to expand the Oring while the piston is moving forward, and contract it when it goes back... If the holes are plugged, it wont expand, you wont get as good compression, if it cant retract, the friction will destroy the Oring and the gun wont run as smoothly.

I use 2 drops of silicon oil in my cylinder, and that's worked perfect for me for the past couple years.

Well, you're not suppose to 'grease' piston heads with heavy, thick (i.e. lithium) grease. You're suppose to lube it with a medium viscosity silicon oil/grease. You can use light weight silicon oil, but they tend to provide somewhat less air seal than heavier weights.

To date, I've greased every piston head that I assemble with plain old white lithium grease, after doing what Stalker describes in stretching the o-ring.

About 80-90% of the time I find that the o-rings are either stuck in the piston head or very stiff straight from the packaging. On some, I'll pull the o-ring right off and "massage" it to loosen it up. Comparing it's "fresh from the package" size to it's post-conditioning size, it's no surprise how much air compression will be lost if you don't do that.

On really stubborn ones, I'll just swap the o-ring altogether. It's only a couple of bucks for a bunch of them at the hardware store.

Too much grease and it'll get blown either out the barrel (which doesn't do great things for your hopup) or pack up in the piston head.

I've never used silicone oil for the piston head...I've always though that an very thin coating of grease on the cylinder walls and a greased piston head o-ring was the way to go.

Anyways...just what I do, it's always good to hear what others do.

Ya, I know how ported piston heads work, I guess you should have initially stated "Never use too much grease". I found that with Apoc's M249, he put in so much grease to artificially seal the leaking and it worked, boosted his fps........... after running about 10 cloth patches through his hop up and barrel to remove most of the grease that got blown int there.

I might try the oil thing though. Last night I wiped the grease (that teflon stuff for AEGs) off the Systema Silent piston head on the gun I'm working on, ran a cloth through the cylinder to get it off there, assembled and chronied it. I don't know what it is, but every ported piston head I've edealt with in the past couple months either gives very low fps, or wildly ranging fps. The SG1 last night, with 110 spring in it, mostly sat around 258-270fps range, and a couple times hit 381fps. Really frustrating. One gun I had success with a TM O-ring on a ported piston head. Another I got fed up and just put the stock TM pistonhead on and left it like that since it gave me the best and most consistant fps readings.

I discovered a leak in my hop hup assembly precisely by putting it in a water tank and blowing in it.
It was a very tiny bit of plastic that got broken, I fixed it with teflon tape.

I also had a problem on a piston head once, specifically the Oring was dead/too small; it Would completely loose compression once every 4 or 5 shots, and the noise is VERY caracteristic and easy to tell.

it needs grease to help it keep a good seal, or at least thats what i was told.

And thats also how it comes, when its new.

And i just meant the O ring, and its not supposed to be slobbed on, its smeared