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V3 gearbox help needed.

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My gear box stopped working . I stripped it down and tested the motor which works fine.
When trigger is pressed. So nothing wrong with motor or trigger contacts one would assume. I did notice that the tapped seemed to have an upward bend and wanted to sit on the gearshift Rather than flat against the gear cog. I reassembled the gearbox and it fired 2 shots before stopping firing.

Any ideas to the problem?

Edited by Monty
Not everything is General discussion. Moved

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Crap battery, motor brushes crapped out is a possible couple of things


try another battery - just coz it is charged don't mean it is in perfect working condition

check wires/connections that they are 100% sound as possible


need more info - could be a mechanical lockup but it wouldn't probably cycle twice

(but how smoothly did it cycle - groaning or firing fine)


motor height - try adjusting that 1/2 turn either way


yeah my first few guesses are motor height, battery crapped out or dodgy connection that arcs under load

your selector plate on cyma v3 ak's shouldn't have a metal strip on it so that rules out an iffy contact at selector/trigger switch


if you have a weak motor with worn brushes, crap battery, poor connections you will get sporadic firing

it is a case of first deciding if it is mechanical lockup or electrical fault - think that electrical might be a problem

but ffs - not got it in front of me to really help much more

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OK so I have just removed the tappet and piston and put it all back together. The motor and gears now turn . now the pick up gear is spinning clockwise. I'm sure its supposed to spin anticlockwise to pick up the piston and pull it back .

(When laid on my work bench Rear of gearbox is to the left nozzle on the right.)


Am I correct in thinking the pick up gear spins anti clockwise?

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The sector turns anti or counterclockwise to draw the piston backwards


If your gears are turning the wrong way then you have a polarity problem at motor.

It should be marked in red or plus sign +


If a motor is running in reverse then the anti reversal latch "should" help prevent the gearbox cycling in reverse


The sector turns counterclockwise or it will smash f*ck out of piston if it runs clockwise. But if you look at gearbox from the other side then the sector will run clockwise from that point of view if you understand


The sector has to turn in the correct way or it will destroy plastic piston if anti reversal latch fails

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Take EVERYTHING is tiny little steps.....

after you have done a few bad rebuilds you will learn just how much you need to check

especially if doing a rebuild or repairing an iffy non-working box which is harder than just a spring replacement


Stuff like PISTON - they are NOT all the same, some can be too tight and the piston can bind/stick as it slides back n forth

some pistons have a longer length or teeth is slightly different position, not much

BUT some can bottom out at rear of box when doing a full stroke on the piston blah blah blah


GEARS - you will never ever shim them with 0.01mm tolerance so don't try that stuff, they need a "bit" of play

normally they will have say 0.20 - 0.25mm play when holding the box together (most try to shim too tight or badly spaced gears)

but as you tighten box up that play will halve at least to leave you with an average 0.15mm to 0.1mm play aprox

(never tighten box up mega tight - those M3 threads strip easy - just tighten with thumb & forefinger and a final nip - not clenched fist)


The bevel height, the amount you shim on top is critical, I can't give you anything like a rough guide but it could be 0.1mm to say 0.3mm

it depends on the bevel itself and bushings/bearings blah blah blah - so check out some shimming vids/guides

you got a v3 which is easier than a v2 as motor cage is better than iffy M4 pistol grips throwing pinion angle out


What I'm trying to say is just take your time and test stuff out in small tiny steps, note what it was like, what you tried, what to put back

examine stuff see how it operates if you replace stuff give it a comparison side by side to ensure the new aftermarket part is going to be ok

(you would be amazed how a fair bit of TM compatible stuff is not so 101% compatible without a bit of mod/adjusting)


You got nowt to lose if it was a bit broke already - heck if it all goes tits up you can either send the box off to a tech

or buy another box or keep the thing for spares - just take your time & I'm sure you will make progress


watch/read some guides - trust me, I steamed in think how hard can it be and my first couple of boxes didn't go well at all

(you can learn by others mistakes - I learnt a LOT by my first few costly ones, which deep down I could have avoided a lot of stress)


excuse any typo/grammar you get the idea of what I'm saying, Best of luck btw

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