Burning Smell???

Hello,
Got a few DC motors that I bought a while back, but never really used. Wanted to use a couple today, so I hooked up a battery pack (3x AA) to two DC motors in parallel. (When I tried in series, the second didn't turn). After 10 seconds or so, I noticed a faint burning smell, so I stopped, and replaced the battery pack with a smaller one (2x AA). The motors were considerably slower, but there was still a burning smell.
Is it due to the fact that the motors haven't been used before, and will go away over time? Or is there too much current going through the motor? (I've never heard of a resistor with a motor) The datasheet says current limit is 0.74A and voltage is 3-6V

Thanks in advance,
TAM

could be dirty, corroded, faulty and/or be an insect in them (had some that had one or all the stated in them that were in my garden shed) . did you use a meter on them (resistance)? or take one apart? other wise still I'm guessing.

If the motors do not get hot, the smell is probably caused by sparking between the brushes and the commutator.

Ideally there should be no sparking, but if it is a cheap motor then you may just have to put up with it.
If the motor can be dismantled, it may be worth inspecting the commutator, and if it is dirty try cleaning it.

JimB

Yes, the motor is very cheap. I have taken the motor apart, and there's nothing wrong that I can see in terms of corrosion, (or insects!!! )
The commutator looked discoloured, so I gave it wipe, and nothing changed (and nothing came off onto the cloth)
The motors don't get hot, so I guess it's something I'll have to live with.

Thanks for all the help,
TAM

New small toy motors like that do not have the brushes run in. If you apply full voltage to them they scream and the brushes arc like mad and it stinks of ozone.

You can run them in by using a much lower voltage so they spin slower and with much less brush current, the brushes will bed into shape.