Need advice - Gearbox upgrades / Dropin
 

Hi all,
I've got a huge compression problem in my M4 (King Arms), and I'm pretty sure the main problem is the piston head having a massive leak. Cylinder head seem to have a small leak too, but even after I teflon-tapped it, I didn't see much change.

So now I'm considering changing the piston/piston head assembly. Might as well change the Cylinder head as well, as I was considering the MASK piston-head/cylinder-head seen here.

Add a Bearing SpringGuide, a good piston (I need advice here), maybe a better cylinder while at it?, shimset as I need one (the lowest gear rubs against the the gearbox's shell when playing in it, seem "ok" when fully assembled :confused:) and the price gets quite high.

Then I realized I might as well go with a Full Tune up kit like this one or a complete dropin Gearbox, as the prices will be quite close to one another...

So what would you think? Are the Full Tune-up kit good at all, or is it still better to choose separate quality parts?

--

Currently:

King Arms M4 CQB with Prommy 6.03mm x 300mm inner barrel
7mm reinforced gearbox
Stock piston (not sure what kind of plastic, maybe polycarb, maybe not), 1 metal tooth
Stock Piston Head - Leaking, Oring is crap
Stock Plastic Cylinder head, 1 oring, bad seal with cylinder
Stock brass, non-ported cylinder
PDI 140% Spring
Stock gears, lowest rubbing against the shell and anti-reversal latch when playing in it. Seems not that bad when assembled, not hearing any screeching, didn't see apparent abnormal wear on the gears

Last time it was chrono'd, gun was firing a flimsy ~250 fps.
As suggested in another thread I made, I stretched the piston's oring, and it helped, but soon after it seems to retract and the problem persist. The more I use the gun, the worst the problem gets.

Thanks for your help

Hello MP!
First, try to change the piston + head. To fix your issue. Maybe cylinder head too.
You could try these but I am not a specialist:
http://shop.ehobbyasia.com/guarder-p...h-bearing.html
http://shop.ehobbyasia.com/madbull-p...ull-teeth.html
http://shop.ehobbyasia.com/shs-cylin...arbox-red.html
This is what I am installing right now.
I can't tell if it is the best choice.

Then you can upgrade the rest of your Gb.
Full tune up kit are maybe a solution, but I prefer choosing my parts one by one :) And take care, it is sometimes bore up kits.
King Arms shells seems to be good quality, as the gears and cylinder too. You could keep it.
Good luck
See you soon!

f.

Take your pistonhead oring out and wrap it around the cylinder. Carefully hear the oring up with a lighter for a few seconds and let it cool. This will expand the oring and create better compression. Try this before replacing anything.

Thanks guys

Funky: The Piston head is the one I told you I bought from Airsoft Qc and it doesn't fit on mine :P Or maybe it's not the exact same one. Anyways

Silencer: I did try this method, but didn't think about heating it. It might just do the trick.

However I kind of made my mind on replacing some parts while playing in there... The piston-head/cylinder-head don't seem that good (that SHS one would have been much better if it would have fit. I suppose a better quality one would be even better)

I've been reading on the ARS MASK Cylinder/Piston Heads, with Sorbo pads, and I think I'll give them a try.

I'm just not sure about piston:
Some states removing the first tooth. Some piston are said to have the SECOND tooth removed for better sector gear engagement. Which one is right, and why?

Also, What about all Polycarbonate Teeth + 1 metal, All metal teeth, or 7 metal teeth? Some people seem to discourage the full metal teeth due to increased wear on the gears, true? What about the 7 metal teeth one then?

I've also seen a few piston with Half Teeth (half the regular width) why is that? O_o

Tried to get some concrete info but found nothing really clear on that matter.

Thanks

Edit: Well well, since I'm a bit in a hurry I went and ordered the Mask Kit from Airsoftparts, along with a few things I needed. Took the StormTech Max impact Piston as well, as reviews seemed to be good.
Now, time will tell. Thank you for your help guys

It's the 2nd and possibly part of the 3rd tooth that gets removed to prevent premature engagement.The first tooth is the thickest one and is the first tooth that gets picked by the sector gear (as its name suggests). Whoever told you to remove the first tooth is horribly wrong.

Ok so if I understand it's not to help the gear to catch the piston but to prevent it from catching too soon when the piston is released? Would make more sense.

Also, nobody really told *me* that, just stuff I kept reading on different forums.

TY

Guarder makes good non bore-up cylinders if ur interested.
They might not be the cheapest ones you can find, but they have a double "o" ring cylinder head and and single o ring cylinder. these fit perfectly with any guarder air nozzle. If you're even interested in getting a new piston, i recommend deep fire's full teeth (given that ur gears are non-hellical). so basically:



Guarder Double O ring Cylinder
Guarder Cylinder head
Guarder Air nozzle
Deep Fire titanium full teeth piston
Deep fire piston head



with this set-up, you can increase your fps by about 50 because no way any air would leak. Hope this helps.

Thanks for the input
Haven't found much guarder parts over the net, especially on airsoftparts where I wanted to order my stuff.

I ended up ordering the stormtech piston and Mask cylinder/piston heads. Hopefully it will yield good results as well.

Hi ! Since you all discuss the cylinder and piston head , may I know what is the type of cylinder head do I need to buy ? long type nozzle or short type nozzle and type #B ... ?
Cause I want to build one new cylinder for my aeg , my old gear box brand is G&P , so I want to upgrade the cylinder part .
Hope to have your answer soon , thank's .

The cylinder port depends on the length of your barrel and stick to the low end of the range.
so if you have a 347mm barrel, you want a cylinder for a 347-390mm barrel
and air nozzles are gun specific, so if you have a marui spec m4, like a g&p, you want an m4/m16a2 air nozzle