Low FPS: Cyma 035

Hello Komrade!

I got another Cyma 035, Stock velocity is in 390-400FPS. So I upgraded the spring w/PDI 190%, metal spring guide w/bearing and JG red piston body w/metal teeth. FPS went down to 290FPS!

So I return the stock setup, orig cyma piston body n sring velocity is only 260FPS!

What happened kaya?

The stock piston (white) when I check the compression my singaw.With the JG it has less or no singaw. Kaya I was expecting the velocity to be in the 430FPS.

Help mga komrade! I was excited after the upgrade to find out I can't even punch a hole on the bottom part of the coke can

Air leak yan komrad...

kasi po komrade what I don't understand nung stock pa cya (not yet disassembled) FPS nasa 390-400. Just the mere fact of opening the gearbox na kaka air leak na po?
Di ko naman ginalaw yng air seal nozzle, hop up chamber or barrel. Just a simple swap of parts (spring guide,spring and piston body)

Like what I did with my A&K M249 I just change the piston body from stock to JG tumaas yng FPS from 390 to 420FPS.

Can you check this part (with arrow) if totally engage (zero gap).
user posted image

This is usually my probs with the two Cyma AKSU (includes my new AK105) i got, putting a hard plastic at back of gearbox is my solution.

That's true! You need to check the gap between your GB and hop up chamber.

komrad Alakdan and Moky,

Please check out photo of my CM035

user posted image

Mukhang no gap naman po

Ok...

Now you have to check the ff:
1.) Piston Head O-ring
2.) The Cylinder Head for possible source of airleak, put teflon on it.
3.) Check the Cylinder Head Nozzle.
4.) Put also teflon on hop rubber.

Common for ACM stock with full of grease that help prevent airleak, when we clean the excess grease, the gun loose a compression.

Dami no? kakahilo! LOL!

I'd check the hop rubber first. Teflon seal it. Then if symptoms persist consult your doctor (alakdan). filakairsoft/clap.gif

OT:
speaking of doctor, my wife is a Physician. Her colleague don't know that i am not but call me also "dok"...well i am an MD, meaning "Murag Doctor". (Murag means "Like")
Korni no?

BTT:
Yup...check first the hop like what komrad master moky says... filakairsoft/aprub.gif

But i doubt ang airleak nasa Cylinder head yan...

Cge komrade.

That's a plausible explaination why it was malakas if left untouch.

Ay naku mga Komrade, as it turns out sira pala yng hop up ko.The front part of the hop where it hold d barrel to the hop unit was detached.kaya pala super singaw.I interchange my other AK74U front and was able to isolate the problem.

Spend another P800 for a king arms hop assembly FPS now is 440 w/PDI 190%

Anyway thanks for the feedback and suggestion po mga komrads!