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Discussion Starter · #1 ·
Hi all, looking for advice on cyma m14 v7 gearbox.
Im new to teching and especially the v7 gearbox. I managed to replace the spring for a sp120 and metal spring guide and it works fine, but i wanted more fps so i orderded a sp130 spring and a lonex v7 cylinder head, as my standard cylinder head has crappy compression and lets by. (Everything else is stock)
I installed the sp130 and new cylinder head, then my problems started. I closed the gearbox and tried to test fire but it locked up. I disassembled again made sure everything was lined up, closed and it did the same again. Open gearbox again, tried the old sp120 spring and lock up again. Put old cylinder head and still locks up. This time i broke a tooth on the sector gear which damaged the piston teeth.
I have ordered a new gearbox and put everything back to stock on my slightly broken gearbox, to keep as spares, but i tested it now it worked first time.
So my question is, is there an incorrect way to line up all the gears when reassembling a gearbox, ie does the sector gear have to be in a specific position like 12 oclock and lined up on first tooth of piston or doesn't this matter?
I didn't think it mattered as the sector gear rotates, then picks up the piston.
I was thinking maybe the piston jumped off the rail to guide it when i put in the stronger springs. Its near on impossible to see if its lined up when i close the gearbox.
Is an sp130 too strong for stock motor to work?
I have cut a small window in the old case so I can now see if the piston is lined up. I will try this when my new gearbox gets delivered.
I dont want to damage the new gearbox so a bit worried about opening it.
 

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Weird! Changing a spring and cylinder head shouldn't have made any real difference. The SP130 should still be within 'doable' limits. There is no real orientation to the gears as the system more or less times itself. All the timing pretty much happens on the sector gear itself (picks up the tappet plate in relation to the piston and also controls the cutoff lever).

Maybe something didn't go quite right in the anti-reverse department? Odd...

On to the subject of more fps...how much did you have to start? Other ways to boost fps are to get rid of the air leaks first. Why up the horsepower if you don't have to? On a big gun like an M14, going down to a 6.03 barrel makes a big difference as does using a full cylinder (if you don't have one already). You can also make sure the hop is airtight. After you've plugged the holes, run it again...You'll be amazed how much you'll gain taking care of those pesky little leaks.
 

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Discussion Starter · #3 ·
Thanks for the info. My Sp120 was prob shooting about 380/390 on 0.2. with hop. Without hop prob about 410. I've put ptfe tape on the hop rubber. How else can i make it airtight? The anti reversal latch seemed to be in the correct position. Hence why i think it was the cylinder not lined up. Would this lock it up? I guess the psiton teeth wpuld havr been chewed up, but it kinda half cycled and stopped. Whats happens when thr motor burns out does it stop completely or just have no power/torque?
 

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Wow, you're definitely not getting the most out of your system. My gun chronos at just over 410 fps with the hop on and I'm running an M110 spring. I run 110's in everything. Mind you, I built a spring gauge to measure spring compression rate as you can't always trust the packaging. The bucking might be ok, but you could be leaking air out the nozzle or even where the nozzle and bucking meet. That's usually an overlooked area but problematic. I also never use teflon tape...I use 'goo' (automotive sealant or gasket maker). It's tricky to use and set up properly, but man does it seal!!!

The cylinder is pretty much go or no go. It can't not line up. hehehe. If the gear box went back together, the cylinder was lined up. Hey, out of curiosity, do you have a hole on the side of that cylinder? If so, was it pointing down or to the side?
 

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Discussion Starter · #5 ·
There is a tiny hole more like a notch cut near the rail guide i guess this was pointing to the side if I remember.
I have ordered a new nozzle with orings to help. But still abit worried about opening geatbox now. If the anti reversal was not working what would that do? Ive attached a photo of my old case with the window cut so i can make sure the piston is lined up.
 

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That is not the proper cylinder for that gun. The cylinder should be filling that entire space.

Should look like this.
 

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M14 cylinders are about 1mm longer then regular ones.

Here is a G&G cylinder in it.
 

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Discussion Starter · #11 ·
Cylinder didnt look like it caught anywhere. The sp130 was longer than the stock spring, that plus the metal spring guide metal it even longer. Would it be too long for the piston/cylinder? And maybe it compressed incorrectly or bunch up in a weird way when compressed?
 

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Which spring guide did you put in?
 

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You don't learn anything from doing it right the first time. hahahaha. Hang in there, you'll get it sorted out. :)
 

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Discussion Starter · #17 ·
Finally sorted it. Got a new gearbox, installed metal spring guide and sp120 spring, cylinder head and shs nozzle. But it only shot about 70fps on 0.2. the nozzle was sticking not moving freely also dont think it sealed well with the hop up bucking as i had good compression at the cylinder head. Removed the nozzle and cylinder head, used stock nozzle and cylinder head. Managed to get it shooting at about 435fps without hop and about 410fps ish with hop on 0.2. so gonna leave it as it is now. The shs nozzle looked same size as stock, but didnt work at all.
 

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Discussion Starter · #18 ·
My cyma m14 seems to be fusy with upgrade parts. Is this the case with the cyma m14? Or just my bad luck?
 

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I've had some misfortune with SHS parts and fitment. Not just on CYMA but anything. G36's, JG, whatever. Sometimes aftermarket parts are close...but not close enough. BUt hey, 410 with the hop on is magical! Well done...
 

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SHS is hit and miss. (Same with ZCI in my experience.) I have had some great parts and some that just do not work.

There are reasons I stick with Lonex, G&P, and Laylax for internals. I am starting to understand the things I have been told as to why Laylax commands the price it does for their parts.
 
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