Hi all again, thanks for your replies.
Just a couple of things, yeah the spring is most definitely in and behind the piston! With the spring guide behind that.
@Sitting Duck - it is a shoddy cyma v2 well done! Everything about it you said is bang on, down to the crappy safety screw.
I'm amazed the teeth didn't strip, the piston must have twisted somehow
but play close attention to the actual teeth on piston say 75% along
You say you changed the spring ???
These China guns have an enormous metal spacer in them by default
(some of them have a "hook" into the spacer like JG or SRC, some don't like Cyma
undo it & bin it, grab a M3 bolt & M3 NYLON LOCKING NUT plus M3 penny washer
The Alloy spacer is about 9mm long or 3 x 3mm teeth pitch
which compresses spring effectively 3 more teeth with it in than removed
3 x 3 teeth in Short Stroking terms will be 3 x M5 in spring terms (aprox)
or 3 x 16.4 fps - 49.2 fps aprox, so you "could" drop the spacer and expect to lose near 50fps
*** NB very rough ball park figure but somewhere about 40 fps I'd say ***
Personally grab another piston if the old one looks iffy
and build it without a metal spacer so spring doesn't compress that 3 extra teeth
Or just fit a M100 to M105 spring is easiest option
could cut spring, some do but you need to finish it properly
Reckon a genuine M100 & new o-ring if compression is crap on existing piston
(with spacer I mean), is about easiest method but there are options
Avoid going nutz, stuff like SHS M4 nozzles don't sit too well on Cyma tappet
tappet is a bit bespoke so has cut outs at side up the front
so SHS tappets need modding or use a Modify tappet plate
(all in all, try not to go too nutz on a Cyma unless you are sad & very bored)
Really it is a cheap half decent gun, but don't go nutz on it
Removing a spacer on a stock piston will drop the weight of piston
perhaps too much tbh - losing about 7gms so piston is say 17gms
instead of say 24gms - great but you do actually want some weight/mass
I would be inclined to drop in a cyma metal rack piston
as SHS pistons might bind in Cyma V2 box at back of box
Simple option is to cut one of the m120's and go with stock "spaced" piston
but you'd need to do it really well and finish properly
magnet under AR latch - tiny round silver neodym magnet under gearbox as others have said
(cheers
@Samurai )
but don't go too nutz & just use it - good pics btw
***** UPDATE ****
JUST HAD A THOUGHT .....
'ere - when you refitted all this together....
Did you drop or did it slip
That tiny tiny metal disc that adjusts motor height on cheapo guns ???
I'm wondering, if the disc slipped off, the motor height dropped
then the box started to wind back the piston a bit without too much stress
then all of a sudden, the strain increases and the motor is too low from a slipped disc
The whirring wasn't the piston stripping, but a low pinion munching up the bevel
THAT could be what was clunking and crunching and jumping - motor height out
coz the tiny disc slipped off and motor dropped about 1.25mm, failing to mesh properly
yeah - more I think about it, that is a possible scenario of how it went pear shape
and sounded/performed real shit
yup the more I think about it, either shims fell off bevel and bevel pinion height changed
disc fell off motor altering motor height
pistol grip/plate not fitted correctly - careful plastic threads strip easy on cheapo guns
somehow the motor height/bevel pinion altered
which it really shouldn't have, but something changed
the bevel/pinion start knocking shit out of each other
(they might be a bit worse for wear now, but not too bad if you just tested briefly)
All that, struggling to cycle gun, it reached 75% retraction, but sector never spun anymore
whilst pinion & bevel start fighting, so the sector or gun never cycles
and THAT is why piston was not released as expected coz motor is no longer turning drive chain
yup - that is my final summing up I reckon says Ace Ventura....
