Your in luck because I have an electric go kart and can tell you exactly what you need to get started and where to find the parts. For the motor I would use any series wound DC motor that is 6.7 inch diameter such as the A00-4009 motor that I use for my go kart. For the speed controller I use an AXE7234 which is rated to work with 72 volt systems and supply 300 amps max to the motor, but you may prefer the AXE7245 which is 450 amps if you like back snapping acceleration. This controller is also highly programmable which will allow you to tune your set up perfectly to have no tire slip at all during stand still take off, limit the current to less than rating, or even limit top speed.
I had the frame custom made by a guy from Youtube, called Mark who has electric go karts of his own that he calls Neurotikarts. You can see an OLD video of my kart back when it was 48 volts if you look up "EEtechs". I recommend that you stick with an aluminum racing frame as they are FAR lighter than my frame is.
For the batteries I use Odyssey PC1200's as they are capable of high discharge and can be deep cycled.
DO NOT USE wet cell based lead acid batteries!!!! If you have pockets full of gold then you can use the more exotic lithium based battery chemistries, but I am not rich like that so I use those PC1200's sealed lead acid batteries.
So for the whole electrical set up here is what I use:
Motor is A00-4009
Speed controller is AXE7234
Six Odyssey PC1200's wired in series for 72 volts (Got these from Summit Racing as they were the cheapest there)
1 AWG welding cable (smaller number means bigger wire)
Ring type battery terminals (not the post type since my batteries came with M6 screw posts)
Curtis 5K pot
1000 ohm, 25 watt, pre-charge resistor
Two RS3 3 channel 6 Amp Bank charger for charging all six batteries independent of each other so no balancing issues will arise.
Parts listed above come from EVparts.com except for contactor and batteries.
Albright SW200 contactor with 72 volt coil came from here:
http://www.tecknowledgey.com/catalog/product_info.php?cPath=57_61&products_id=530
Be sure to have the following options selected for the contactor:
72 volt coil
Magnet Blowouts = YES
Coil type = Continuous
L bracket option
Suppression = YES
DC coil
My go kart specs:
Top speed with 4:1 is 48 MPH, with 3:1 is 55 MPH.
Weight without driver is about 450 LBS.
20 HP approx.
Runtime is 20-35 minutes at 4:1 ratio depending on how crazy I am with the burn outs.
Tire diameter is 11.5 inches and is a 4.10X3.50-5
Current is set at 240 amps in the AXE controller and throttle up rate is at 10.
A00-4009 motor timing advanced by 5 degrees.
If you need me to draw up a schematic of how to wire this up then let me know.
