I'm attempting to build an electric motorcycle. My motor is a Leeson 130v DC,. 3 horse, 3500rpm, 54fp. Motor. I'm planning on using a small generator to power it. Like a kind of hybrid. The question is how do you turn AC 120 into 120 DC?

 

Use a Bridge Rectifier with regulator if you need to lower the voltage.

https://www.ibiblio.org/kuphaldt/electricCircuits/Exper/05188.png

 

I'm planning on using a small generator to power it.

'Small' being > 3HP.

 

So what you end up with is a bike that has a 5 HP engine driving a ~3000 watt generator head that produces the electricity to power the 3 HP motor adding at least 40 - 50 extra pounds of gear to the bike that is doing nothing to help the efficiency of converting fuel energy into mechanical motion.

Got it. It's target market group is government officials right?

 

You don't need the capacitor for a DC motor.
The first problem I see is, how do you make a hybrid when you need 120 volts worth of battery?
Install 10 car batteries? Use a 2KW inverter?
You can make an electric bike out of what you have, but a Hybrid vehicle doesn't seem practical from this starting point.
It seems like you should remove the generator from its motor and attach a centrifugal clutch to the motor. Less parts, more efficiency.

 

http://www.alibaba.com/product-detail/3hp-economic-silent-gasoline-generator_1654585783.html this is a 3hp engine and a generator, it weighs 40kg.

 

That hybrid configuration is way too much of a heavy kludge to put on a bicycle.

 

Turning 120VAC into 120VDC is very much the easiest part of your project. You're going to find many far more challenging issues.