G36 low fps problem

[Morra]

After a friend showed me how a mechbox works and how to take it apart, i decided it was time to do my first upgrade on my jg g36c.

Inside i have a
Pdi 140% spring
Modify parts:
Type 1 Enhanced ported cylinder
Stock cylinder head with sorbo pad
POM Air Seal Nozzle
Polycarbonate Piston
Polycarbonate Piston Head with bearing
steel bushings
tappet plate
Bearing spring guide
Promothius hop up rubber.
and also a madbul 363 6.03 tighbore

The gun cycles perfectly, however the fps is less than 290, it does not puncture the side of a canada dry can, and the range is very bad.

What could i have done wrong? Could it be the gear timing?

EDIT: their was no problem, i was using 25's, my friend mixed up my ammo supply:banghead:

[TriChrome]

Gear timing doesn't really exist... after the first shot everything would reset.

Most installations with FPS loss is due to the hop-up bucking installed incorrectly. Lube up the bucking and try again.

[m102404]

Gear timing is a myth...doesn't exist...but you do need to make sure the nub of the sector gear is not directly under the tappet fin and it's never a bad idea to make sure that the sector gear teeth are started into the piston when you reassemble.

Do you have the port of the cylinder furthest away from the front of the mechbox? If you have it reversed (i.e. the port at the front) you'll end up with a very low FPS.

Did you put the spring in the right way? If you have a non-linear spring (i.e. there's a tighter bunch of coils on one end of the spring than on the other)...the tighter pack of coils goes at the rear (i.e. closest to the spring guide).

Those are the obvious/easy ones...then you get into the tougher ones that deal with air leaks.
1. how is the compression of the piston head/cylinder without the nozzle?
2. how is it with the nozzle on but in the extended position?
3. how is the airseal between the nozzle and the hopup unit/rubber? (that it's cycling nicely is a good first sign that all the parts are fitting)

Best of luck,

Tys

[Spa]

1) check that your hop up rubber is set up correct (get a gun doc to show you how)
2) your new ported cylinder may not be the right one for the barrel length. - Check with water to see if when you fill the barrel up with water, and pour it into the cylinder, the water should reach near where the port is. if its to low or over the port you can get air problems when they exhaust the barrel.
3) check for piston compression. - its a common problem that the o ring on the piston head is not making contact with the cylinder wall. (cover the cylidner head nozzle with a finger and push your piston up and down. you should feel pressure build up. if not you have a contact problem and needs to be re-greased or the oring changed)

Those are the most common problems, if those dont fix it, we will have to go into complex solutions

[zone 69]

Did you do a compression test on the cylinder before installing it, maybe your piston head O-ring need's a strech and a lube.

[Jimski]

Type 1 Enhanced ported cylinder

is it bore-up ? i.e. does the piston head match the cylinder?

[Spa]

Originally Posted by Jimski

is it bore-up ? i.e. does the piston head match the cylinder?

http://www.airsoftparts.ca/store2/in...roducts_id=777

Doesn't seem to be a bore-up!

[Morra]

Originally Posted by Spa

http://www.airsoftparts.ca/store2/in...roducts_id=777

Doesn't seem to be a bore-up!

No it is not a bore up

I have tried with both the stock and new hop up rubber, and still not able to penetrate the coke can, unless i make one side flat and then shoot it. Also, i ran out of .20' and all i have are .25s, and they are still unable to puncture it unless i flaten the side.

[The Saint]

Is the cylinder oriented the right way? Should be front |----O--| rear.

[Morra]

Originally Posted by The Saint

Is the cylinder oriented the right way? Should be front |----O--| rear.

yea the port of the cylinder is facing the rear of the mechbox

[Flatlander]

You should be shooting around 340fps with that 140% spring. Your FPS estimate, is that with .20's? Because 290fps on .25's is ~330fps on .20's.

Do you have your hopup turned all the way off? I've seen a 100fps difference on one particular gun because the hopup was pretty much cranked all the way on. I shit you not, I have a chrono to verify it. I find properly adjusted hopup knocks off around 10-15 fps, FYI.

[Spa]

shouldn't matter on a G36. But really try the piston compression thing where you block the cylinder head nozzle with your finger and rub one off.

[Morra]

Originally Posted by Spa

shouldn't matter on a G36. But really try the piston compression thing where you block the cylinder head nozzle with your finger and rub one off.

What do you mean rub one off?

[dpvu]

Just block the nozzle with your thumb and try to push it into the mechbox. It should be relatively difficult with a good air seal. If it's easy to push, that means you've got an air leak somewhere.

[CDN_Stalker]

I'd say start by getting rid of that 140% spring, PDI springs in past years have been junk (I've checked out a half dozen of the PDI 150%, they range in length between 6 3/8" long to 7", and a lot of the bad ones are made of a thicker wire than the "good" ones), a 150% spring could net you anywhere from 340-450fps. Get a Modify 100 spring from Jugglez, will be easier on your mechbox and more consistant too.

Sounds ike an airleak issue overall, check out everything that seals from the cylinder/pistonhead O-ring, make sure the O-ring inflates properly, then check cylinder head and nozzle mating, then hop up rubber and alignment.

This is also a case of over-upgrading biting your ass. KISS is always best when it comes to upgrading an AEG, but then it all depends on the brand. And not all upgrade parts are created equal, there is some real crap out there that is sold, and that includes big name brands. Best I've found across the brands is Modify, never had any issue with anything by them, yet have seen and found many issues with some Systema, Guarder, Prometheus parts.