Cylinder Compression Maintenance

[Jon The Student]

Good afternoon, I was curious as to how folks do their compression jobs specifically, and Google'd it to find this thread on Pyramyd Air.

http://airsoft-guns-blog.pyramydair.com ... rsoft.html

Out of curiosity and cautiousness, can anyone attest to these methods and their effectiveness, or better yet, could you please inform the rest of us common folk on what you do to improve air compression?

Thanks and have a nice day,
Jon

[Star_folder]

http://www.airsoftforum.com/board/test- ... 22834.html
That's how I test for compression leaks, and I believe I go how over how to fix some of the more common leaks in the system.

In my experience, I've found that the hop up and nozzle leak more than anything else in a system. Especially in high pressure systems, aka, high fps. These require a bit more work, as you can't simply replace an o-ring and everything is dandy.

[Dominum]

I didn't watch the vid, but I glossed over the text. Seems like he knows what he is talking about, but don't use teflon grease for compression, use silicon oil. Nothing with aerosol, pure 100% silicon oil and preferably a higher viscosity then what you normally put in propane adapters. Properly sized Orings (or Xrings if you want top notch consistency, but the difference for AS is not significant), proper application of silicon oil, proper use of teflon tape on stationary things, and the right parts are all important. You obviously get better seals between the airnozzle and cylinder head with an Oring airnozzle as opposed to most stock ones, and teflon tape between the cylinder head and cylinder are always good. Using a high polish cylinder can help a little, as will an aftermarket Oring that is slightly thicker than stock ones. Always inspect individual parts if you are having a compression issue. There are tons of places air can be escaping; cracked (even hairline) piston head, torn Oring, scratched Oring, scratched cylinder, too much grime (a combination of metal filings and grease usually) on the Oring or inside the cylinder wall, a poor seal around the cylinder head (teflon tape fix), a cracked cylinder head (rare), a mismatched air nozzle and cylinder head, a mismatched piston head and cylinder, a mismatched cylinder head and cylinder, a cracked air nozzle, too much grime between the air nozzle and cylinder head, a loose hopup chamber (teflon fix, be careful to avoid harming function when wrapping), a cracked hopup chamber, a torn bucking, too much grime on the outside of the airnozzle, mismatched air nozzle/bucking/barrel/hopup chamber.

When it comes down to it, compression trouble shooting or improvement is a matter of process of elimination. Verify that there are not problems with the parts themselves (cracks or tolerance issues), and then move on to improving each place where it is possible for air to escape. Take your time and pay attention to details, then test to confirm. With stationary seals (such as between the outside of the hopup bucking and the inside of the hopup chamber) silicon oil and teflon tape are the usual fix. With moving seals, (like between the piston head and cylinder) the solution is (assuming everything is already cleaned, grime is bad for seals, since it is composed mostly of tiny metal shards) larger/thicker Orings/Xrings and proper lubrication.

Remember that there are two functions of the lubrication in your gearbox. Between high friction components, like gears and bushings, the sides of the piston rails, etc.; a lubrication is needed to reduce heat and wear between components by lowering the amount of friction between the parts when they rub on each other while they spin or slide. This lubricant should be of a relatively high viscosity to perform it's function well and stay in place. Silicon oil does NOT perform this function well at all, and that's not what it is made for. For these parts, use something like a teflon/petroleum/molybdenum/lithium etc. based lubricant. Though white lithium grease is popular, it has a tendency to dry out with low humidty or swell with high humidity, and this often prevents it from performing it's function. I used to use it until I saw this happening and looked into it. Now I use a lithium grease that is petroleum based. It is therefore not impacted at all by water and doesn't dry out. It is high enough viscosity to largely stay where it is applied, and for that I use a syringe (about a 1mm nozzle or so). The other function of lubrication in your gearbox is to maintain a tight air seal, reduce friction, and keep Orings performing well. For these places in your gearbox, silicon oil is ideal. Again, no aerosol (anything that sprays from a pressurized container). Though lower viscosity silicon oils will work, the higher ones will work better. A good example is the viscosity difference between the silicon oil made for GBBs and the silicon oil made for Tornado grenades. The latter is a higher viscosity and IMO is ideal for gearbox use.

[Romba]

Slightly on the same topic. I have had my gun for over a year an have never lubed anything. What do I uhh what do I do? Any guide that you can link for basic lubrication stuff? Mucho gracias.

[Dominum]

Well, that pretty much explains how to lube everything except the gears and piston. Lubrication is needed between the piston rails and the side of the gearbox shell, and between all of the axles of the gears and the bearings. Also, along the side of the tappet plate isn't a bad idea. Just use the principals I explained before, if there is friction and you want to minimize it, lubricate. Obviously you need to clean all the crap out first, after you take the gearbox out of the gun and open it up. Don't be too liberal with it, there's no need to slosh it all over the place like a Chinese assembly line employee.

One place that does have friction but you DO NOT want to minimize it is between the cutoff lever and the sector gear. You WANT as much friction as possible here, because that is how it performs its function. Clean these two surfaces and do NOT lubricate them at all, or you may not have a very reliable semi auto function.

I just knocked my prices down since I have more spare time for airsoft, a full tune up with cleaning, new Oring, GB compression work, lubing, and shimming is only $40. Alternatively you can do it yourself under my supervision free of charge. Click the link in my sig for more details,