Racing Power Wheels Part 4: Project Update on the Motor Kit and Batteries


So more progress has been made with the Boca Dune Racer project. Parts were ordered before and most of the parts have arrived. The first thing to arrive was the motor kit that was ordered from The motor kit was the 36V 1000W MY1020 motor with an universal controller and a hand throttle.

Batteries were also ordered from Monster Scooter Parts, 12V 18Ah sealed lead-acid batteries.

So below is a picture of the controller from Monster Scooter Parts.

This motor controller has a rated maximum current of 28 amps. As you can see in the picture above, the hand throttle had a broken piece. Everything came in 3 different boxes because of all the weight from the batteries and the motor. Somewhere along the way, the hand throttle was probably crushed by the motor. But a phone call to Monster Scooters quickly resolved this issue. They quickly shipped out another replacement without a hassle. There was also another grip that came with the kit that can be placed on the other side of a handlebar.

The motor in the kit is a MY1020 36V 1000W motor. Pictures of the motor can be seen below.

The motor has a rated speed of 3000 RPM with a rated current of 35.6 A. Below is a picture of the specifications found on the motor.

The batteries I got for this project are universal 12V 18Ah batteries.

Initially, I was going to go with 15Ah batteries but these 18Ah batteries were only $10 more and they came with free shipping. So I decided to go with these batteries. Also, I didn't go with the 24V 650W motor kit no more since they were out of stock until March. But now we're close to March so maybe I could have waited. But this 36V motor has a higher rated speed so we would get a higher top speed than going with the 24V motor which had a rated speed of 2600 RPM. I emailed someone from the Power Racing Series regrading shipping costs and I was told that shipping does not count towards the $500 budget.

Below are some pictures of the 12V 18Ah batteries.

The MY1020 motor comes with a 11 tooth 8 mm sprocket that wouldn't be compatible with the sprocket that I will be using for the axle. The axle will be using a #35 chain size sprocket from BMI Karts. So I decided to remove the sprocket from the motor and take some dimensions to be able see what's online to replace the sprocket with a #35 sprocket. So to start things off, I needed two wrenches to remove the sprocket. One wrench goes on the nut while the other wrench goes onto the motor's shaft, as seen below.

The nut is a 12 mm nut while the motor shaft was held in place with a 9 mm wrench. The motor shaft has flat spots where the wrench goes onto to hold in place. Also, the nut wasn't your standard threaded nut. To remove the nut I had to turn it to the right, clockwise, to loosen the nut. Regular nuts are loosen by turning it counter-clockwise.

Once the nut was off, I could then take measurements of the motor shaft where the sprocket slides onto to find a new sprocket that can fit there. The sprocket on there is a double D bore sprocket. This can be seen below.

With the sprocket off, I could then take measurements of the shaft. The width between the two flat parts of the motor shaft is approximately 8.1 mm.

The diameter of the motor shaft that is not flat is about 10 mm, as shown below.

So the main important number is 8.1 mm which is approximately 0.3189 inches. So I have to look around until I could find #35 sprockets that can fit this motor shaft. I can try to find a sprocket that has a smaller bore than this and I can try to attempt to machine a Double D (DD) bore into it. Another alternative that I've been thinking about is to look for a sprocket that can fit over the 10 mm portion of the motor shaft and use set screws to look onto the flat parts of the double D bore. 

I found a nylon #35 sprocket at McMaster-Carr with a bore of 1/4" which is approximately 6.35 mm. So I can machine it to fit onto the shaft.

This type of sprocket will be easy to machine into since it is made out of nylon but I don't really know the durability of the material when it comes to actually using it with the motor. But this sprocket may be suitable, and it's only $11.75.

Another alternative is to maybe find a sprocket that can fit over the 10 mm portion of the double D bore. Then I could possibly use set screws to set it onto the flat portion of the motor shaft. I found different sprockets on MCMaster-Carr that come with a 3/8" bore which is approximately 9.53 mm. So, it is smaller than the motor shaft but it isn't much smaller. So I can try to bore it out a little more to make it fit snug over the 10 mm portion of the motor shaft. Then I could try to machine some threads into the sprocket hub to insert set screws. The list of sprockets from McMaster-Carr can be found below.

At the link above, sprockets for chain #35 chain size can be found with a 3/8" bore. These sprocket also come with 2 set screws that I can use to lock onto the motor shaft. The price of a 9 tooth #35 sprocket with a 3/8" bore is $10.66.

This other sprocket also seems to be suitable.

I'll look more into it and see what are my options when it comes to finding a sprocket that will fit this motor shaft. It is really difficult to find #35 sprockets that will fit this motor shaft since #35 sprockets are usually in inches and this motor shaft is a metric one.

So I decided to go ahead and test the motor but the motor did not turn. I had the batteries connected in series as shown below.

I then connected the batteries to the thick black and red wires found on the controller. I connected a switch I got from RadioShack to the "power locks" connector. I connected the 3-pin throttle to the throttle connector, labeled as "to put" connector.Finally, I connected the motor to the thick blue and yellow wires.

The switch that I am using has a built in light that will emit once the switch is flipped to the ON position. I flip it on and the light lights up. I checked the voltage across the 3 batteries and got somewhere around 38 volts. But when I twist the hand throttle, the motor doesn't turn. So I checked the voltage across the signal wire coming from the hand throttle and the signal voltage changes from a low voltage to around 4 volts. So I know the throttle works. But, when I check the voltage across the motor connectors, no voltage is found.

So I called Monster Scooter Parts and they quickly sent me another motor controller, just in case this one was a faulty one. But when the new motor controller came, I had the same problem. So I'm not sure if it's something that I am doing wrong or maybe these controllers were a bad batch. So I will be contacting Monster Scooter Parts to return the controllers so they may test them. I even shorted the "brake" connector to make sure that wasn't the reason why the motor doesn't turn.

In the mean time, I ordered another controller from another company called TNC scooters. The controller I got can be found at the following link and be seen in the picture below.


  1. well defined measurements or dimensions with great innovation.

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