Possible explanation for motor not being able to make the mechbox run
 

This is my first time gun-docing.

I have decided to rebuild a Cyma MP5J. Here is what I changed on the mechanical side :

All gears are high speed modify gears
New piston (marui), cylinder, piston head, cylinder head and spring guide.
Modify tappet plate
Modify selector plate
M100 modify spring
Jing Gong black mechbox shell

I also did the shimming. The gears could very freely spin in the mechbox beofre putting in the anti-reversal latch.

Marui EG1000 motor running on a 8.4V 1000 mah mini battery.

When I test the motor outside the mechbox it works fine.

When I insert it in the mechbox nothing moves. I see inside the motor a little part trying to move but it stops and the wires heat up quickly.

I guess something is blocked in the mechbox or something but what do you think could cause this?

Did you actually close the mechbox and completely screw it tight when testing your shimming?

Yep. All screws in and all.

My guess is some part is not well-placed (although I followed mechbox.com very carefully). Just wondering what are the most risky parts in a mechbox that could cause this.

Only other thing I can figure is piston. The only real moving parts right, so its most likely gears or piston issue. Were the piston guides around the grooves in the mechbox properly and everything when it was closed up?

And are you sure the battery is charged? If it isn't charged very much, it might still turn the motor out of the box, because there is no load/resistance, but inside it fails.

check the motor polarity, if its wired backward it will do that... (no fire and heat buildup)

edit: also can you move the bevel gear with a screwdriver before putting the motor... yes = bad motor or reverse plugger motor no = something jammed in mechbox...

Check polarity.

+1

If you just hear a click every time you pull the trigger, it means that the motor polarity is not right(gear is being stopped by the anti reversal latch). To solve it, just connect the red wire to the other pin and the black one vice versa.

or... height adjustement... could have been modified with the new shim job

Tried inverting polarity. No results.

Guess I will re-open mechbox and check for piston alignement.

Keep ideas and suggestions coming!

Yeah motor height adjustment would be the next thing I would think of, as lemegacool said.

Might be that your battery isn't powerful enough to pull that spring, especially with highspeed gears as well.

First thing I would try in this situation is throw on a 9.6v large or a lipo.

Usually solves the dilemma right away.

Yea, people always over estimate their battery charge... Try with another fully charge battery.

+1. If you need it to work ASAP (as in, game coming up before you can get new stuff in), you could try putting in the stock ratio gears from the CYMA. That battery MIGHT be able to power it then.