ICS M4 lower gearbox not working properly

[heikis]

hi. got a problem with the lower gearbox. if i let the lower gearbox to run for about 10 seconds (i have removed the upper gearbox) then i start getting some horrifying crackling sounds. i dont touch the gun for about 1 hour and the gears then seem to run properly until I again have spinned them for ~10 seconds and that crackling starts all over again. i havent opened the lower gearbox yet.

i dont know if this helps or not but with the upper and the lower gearbox working together the gears seemed to crash and refuse spinning at some point as if the battery had died on me (i could feel and hear the twitches of the motor). the solution was to reset the gears and then it all worked until the next point of a "crash/empty battery effect". i thought it had something to do with a bad piston so i switched the ICS alu piston for a marui plastic one. 2 shots and the first tooth of the piston was shaved off with a big chunk still hanging.

whats going on? i bought the gun second hand and havent used it much. feel free to ask for additional information. im not very familiar with the inner life of gearboxes. thanks ahead for any kind of help!

most of the time that i know of, the gun was used with the ICS aluminium black piston with a red pistonhead (maybe the ics oversized pistonhead) which has many holes in it

[AngelusNex]

Might be broken teeth on one of the gears. You're probably going to have to open her up and see whats what.

[Defcon_Carl]

im not a gun doc but i would assume its something to do with shimming and motor height alignment.

[heikis]

thanks. i will look into those possibilities.

could the bad shimming and/or a broken tooth of the lower gearbox be the cause of a shaved piston tooth?

[AngelusNex]

Honestly... Tm internals aren't all that great. Was probably just a shit piston... OR... are you running a very powerful battery? or lipo?

[dpvu]

Are the gears and motor stock? ICS' pinion gear is a bit different from the ones used by TM/CA etc. so if you replaced the motor or changed the bevel gear, you need to change the pinion gear as well. Also check your motor height but your bevel gear may have already been eaten up.

[heikis]

havent tried with the ics 3000 because it is broken.
i am using tm eg700 with the stock gear inside the lower gearbox.

actually i had a "CA high performance high torque" motor inside when i bought the gun. the weird thing is that it only worked with 11,1V lipo. with my own 8.4V and 9.6V large nimh it wouldnt run :/

[dpvu]

That might just be the problem. Find someone with a pinion puller and swap the pinion gears on the ICS Turbo 3000 and the EG700. I forget if the ICS pinion is more or less steep but the TM pinion might not be meshing with the ICS bevel gear well.

[heikis]

i solved the "crackling sound problem" with a brand-new ics 3000 motor.

however i got another problem regarding the lower gearbox. problem is that on semi-fire mode it fires full-auto, but not all the time:
If i pull the trigger nicely and to the end, then it fires a nice 1 shot as supposed. but if i pull the trigger not to the "end" then it fires full auto. and the full auto wont stop until i release the trigger.
so in order to fire shot by shot on semi-mode i need to pull the trigger fast and firmly.

the gun has been to a gunsmith and he couldnt tell what was wrong as all the internals seemed nice and not worn out. the lower box was taken to pieces and every piece, that could have been the source of the problem, was examined. nothing came up.

thanks for any given ideas

[m102404]

I strongly suspect (and bear in mind this is all guessing through the internet sight unseen) that your switch assembly is dying/burned/corroded or the contacts are bent out of position.

The crackling sound might have been arcing between the switch contacts...and if you're running large 9.6 or 11.1 batteries...they'll eat up a switch assembly in good order.

At the beginning of a burst...the battery was at rest and had time to "charge up". Later on in the burst, it's discharged and the amount of power it can supply might be marginal (especially with a burned switch assembly or marginal motor).

Feathering a trigger only aggravates burning out a switch.

With corroded/burned/oxidized contacts...you're starving your motor for power. A "stressed" motor heats up...degrades it's internal magnets...and gets weaker. The crackling might have been shorts in the motor as well.

A funky trigger pull is sometimes indicative of a mis-match/worn trigger and/or switch assembly.

The shaved teeth of a plastic piston is indicative of early engagement or poor angle of engagement between the sector gear and the piston rack. While the "trimmed" teeth may not cause any further issue...the bits of plastic that came off of them aren't good for the internals of a mechbox.

Anyways...all just guesses.

Best of luck,

Tys

[heikis]

finally, with some thorough testing I found the source to the problem of gears wrecking my pistons. i had a 100% working upper gearbox and my faulty upper gearbox to switch parts and figure out the solution. it became clear that the combination of my cylinder and cylinder head was bad. the cylinder and cylinder head were stock ICS and without any visible damage nor wear. i tried out many combinations and withput hesitation that's where the problem is.

my options are to buy a new ICS stock cylinder head or a metal one. i will get whichever i can get quicker.