best electric generator?

thingiverse

this is the best electric generator that i have so far. powering the engine with 5 vol at 280ma can produce 120 Mah at 3.9 v AC current. when i use an electric motor as a generator and apply the same power i am getting 2.39 v at 1.3 Mah DC current. my generator in my testing is better but i do not know if my multimeter is failing. if someone can build it and test it so i can confirm that my generator is better and start to design a much bigger version capable to generate much more power. The electric motor i got out of an old DVD reader.