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[on:]

What's the purpose of those capacitors? What would happen if I would bypass them?
Thanks in advance!

[Reply #1 on:]

I think they are there to absorb some of the very nasty electrical noise caused by the DC motor.  You can remove them if you don't mind the electrical interference.

[Reply #2 on:]

Yep, they're to reduce noise, just as John says. Where it says 'soldered to the outside' - that means you solder one leg of the cap to a motor terminal, to other leg to the motor case next to the terminal. The noise absorption is superior to a single cap across the terminals.

[Reply #3 on:]

Thanks alot guys for the quick and informative answers! 

[Reply #4 on:]

The brushes on brushed DC motors generate sparks which are the source of the electrical noise (in
the radio frequency bands).  The caps reduce these higher frequencies to much lower voltages thus
preventing the motor leads acting as noise-transmitting aerials.  The value is chosen to be large
enough to remove a lot of the noise but not so large as to overload the motor driver circuit when
it uses PWM.