This motor kit draws about the same amount of current as the 24V 650W motor kit. From the equation P = I*V, the 36V motor draws about 27.8 amps while the 24V motor was going to draw about 27.1 amps. So I expect similar run times except that the 36V motor will require 3 12V batteries to run it. So this changes the amount of what we have spent into the $500 limit. This kit runs for $179.99 and the batteries we have chosen was the 12V 18Ah batteries http://www.monsterscooterparts.com/gr12vo18amph.html. We had ordered 24V battery packs that was intended for the 24V motor kit. The 24V battery packs go for $109.99. So one and a half of those packs would go for about $165. Only half of the cost of the batteries goes towards the $500 limit. So right now we are currently at $262.50. So that gives us a less amount of money to go towards the rest of the build, $237.50. At the time of ordering, I forget to consider the increase of cost of the batteries. But I'll try to work with what I got.
So there are many options out there to be able to make a live axle for a go kart or for this modified Power Wheels project. I am planning on just getting rid of the whole rear end of the power wheels and just keep the metal frame. I will keep the plastics that rest on top of the existing motors and figure out how to mount them on again later on. I will need to check underneath the plastics to see if there is any sort of metal connection between the two running square tubing going from the front to the back. If not, then I will need to either weld/bolt on an additional square tubing between the two square tubing running from the front to the back.