P90 reversed firing modes

[Broketoon]

Seeing as the title may not be clear, my King Arms P90's automatic is firing single, and the semi is firing full auto...

To add more info.
during a game the OEM trigger assembly ate itself (terrible :S), so I purchased a very hard to find replacement (cheaper then a complete gearbox) from Classic Army (the only one I could find, and the compatibility said it was good for king arms)..

put it all together, plugged in my 9.6v as my 8.4 is currently charging...and bam, full auto fire on the semi setting, and semi automatic (sometimes burst) on the full auto setting...even outside the gun its firing that way.

wiring backwards? that weird latch thing on the left hand side not working? (no idea how that works anyway so that might be me not putting it on right)...user error? what ever the case, any light that can be shed on this issue?

[lurkingknight]

the semi trigger on the p90 is like a v2/3 setup, there's a shuttle that gets pulled back by the trigger that pulls a little metal block between 2 metal prongs to close a circuit and cycle the gun... when the sector cycles, the cam on it moves the cutoff arm and flips up the shuttle and it resets because it's spring loaded.

Your problem here is that most likely the shuttle is getting caught in the prongs and the cutoff level doesn't have the force to pop it free. You need to pry the prongs open just a tiny bit to make it just tight enough that it will cup the block, but not so tight the block wedges in.

The other issue of a non working semi in a p90 is a worn cutoff lever.


The auto trigger is activated when the trigger is pulled back all the way. The front trigger shuttled would have already reset forward, but there's another 2 sets of contacts that get closed by the bottom of the trigger assembly so that will fire the gun continuously. If you're finding yourself having to pull back really hard to get it to fire full auto, the 2 prongs need to be bent forward ever so slightly to meet the trigger block sooner.

It could also be possible that the front trigger block is being held so tightly and that your rear trigger isn't even completing a circuit so the cutoff lever takes a few whacks to get the block to reset in the semi trigger.

if the semi contacts are too tight, a p90 will keep firing till that block resets, full auto, trigger down or not.

[Broketoon]

so whats with that lever on the left side of the gear box?
and from what I can see, the semi auto contacts dont hold onto the block, but just barely touch it...

edit: so thats the lever* noticed I completly misworded a sentence...it doesnt seem to be doing anything...maybe i installed the wire harness on wrong?

EDIT EDIT
FIXED...after a little tweaking and working the trigger mech, i seem to have "broke it in", now works perfectly...if I have any further issues ill post again ...thanks for the tips though Lurking, bending the contacts seems to have also fixed the infamous p90 semi-fire seizing issue o.o

[Dolly-lama]

Found this post looking to fix my KA p90 which has a slightly different problem, thought one of you might be able to help.
I just got mine in dec and ive played about 10 games and most through the winter with no problems
My gun is stock and im running .25s with a 7.4 lipo.
2 weeks ago my semi auto mode decided to turn into full auto, but my full auto is still full auto. This gives me effectively 2 full auto modes.
i know nothing about the internals of airsoft guns as i have just switch over from paintball. but i have read above and now removed my gearbox. the half pull semi auto function does not exist, it did before. the shuttle is fine, the return is fine, but the gearbox registers the semi contacts as full auto! i half pull for semi and hold it goes full, if i then full pull it continues to fire full without skipping a beat, or this case a shot.
Help!

[Hectic]

Sounds like a broken/worn cutoff lever.
basically that lil lever u see on the outside of the box has a portion inside the gearbox.
That little portion rides on a cam (a lil teardrop shapped bit on one of the gear shafts) once it(the lever) hits the point/tip of the cam it slightly lifts the shuttle (the moving bit of the trigger contacts) off the trigger and the return spring pops it back to battery.
If the lever is broken or worn out the gun will just shoot auto on semi.
it could be the trigger shuttle itself but if that breaks/wears youll normally just get a click sound as the shuttle pops off the trigger so prolly its the cut off lever.

[Dolly-lama]

Thanks for getting back to me so quickly. I actually just figured it out myself like 5 minutes ago lol (its the worn cutoff lever)
knew it wasn't electrical and something had to give in the box so it makes sense it is the easiest piece to change!

Thanks again!

[Hectic]

No problem