Razor MX Upgrade Kit Install

My sons favorite thing to do is rip around on his Razor MX500. It was a great training tool for him learn how to get comfortable with a throttle. Overall maintenance is very low, the only thing I’ve had to do was replace the batteries. The max speed of the MX500 stock is 14mph. That was great for him for a while but when he turned 7 it was time to turn it up! I had to replace the batteries anyway so I thought this was a good time to upgrade the entire system. The stock system runs off a 36v controller with a 500 Watt motor. I know a lot of people who upgrade these bikes step up to a 72v system with a 3000 watt motor. I think this over powered for most 7 year olds and the 72v batteries are very expensive. I decided to settle on an upgrade kit that was 48v controller with a 1800 watt motor. I also upgraded his battery to a 1800 watt lithium ion battery that was 20 amp hours. I’ll break down the total cost and install so follow long!

Cost Breakdown

• 1800 watt Motor, 48v controller, throttle assembly $120 (I scrapped the throttle assembly)
• After market throttle assembly with voltage meter $22
• Key ignition $11
• 1800 watt 48v Lithium Ion battery 20 Amp hours $322
• 40 amp junction box (to make wiring easier) $9
• Velcro straps (to attach everything) $12

Total Cost $496

I purchased everything from amazon and ebay. The biggest decision by far is the battery. There are so many options and the cost varies greatly. The reason I went with a lithium ion battery is because I could purchase one with my desired voltage and wattage output without wiring a bunch of 12v lead acid batteries together. When you wire 12v batteries in series you do not increase the amp hour capacity. You are limited to your lowest amp hour battery. This means you would have to by extremely expensive high amp hour lead acid batteries and have to buy 3 or 4 of them depending on your voltage. You would easily surpass the cost of a good lithium ion battery. The longevity of the lithium ion battery is also much higher than that of the lead acid. Most lithium ion batteries can sustain several thousand cycles.

Battery Replacement Dangers

Whatever battery replacement you decide its worth noting that a lot of budget battery options are not sealed. I would not use anything besides a sealed lead acid battery if you are looking for a cheaper option. Non sealed lead acid batteries off gas hydrogen gas which is toxic and explosive. If gas buildups it can ignite from the spark of your charger or from any electrical shortage within the wiring system. This not something you should not risk! Buy sealed lead acid batteries or lithium ion.

Tools

• Cutting wheel
• Drill with 3/8th drill bit (one that can cut metal)
• Screwdriver
• Velcro Straps
• Electrical tape
• Electrical connectors (assorted)

Motor Installation

Most motor upgrades come with a small bracket that you will have to remove. I cut this off with my cutting wheel and the metal was very soft. Once you start to cut in you can easily pry off the bracket with plyers.

Next you will need to counter sink the screws that hold on the end covers of the motor. They stick out and will prevent the motor from mounting into the swing arm. First you will need to remove the screws holding on the end plates. I then used a drill with a 3/8th size drill bit to remove some material on one end. This allows the screw to sit in flush. Make sure to not remove too much material so the screw can still hold the end plate on.

After this completed the motor will mount right up. If you chain doesn’t line up then you will need to adjust the rear sprocket so the chain wont jump off the sprockets. Here is a write up how to do this.

Battery Install

This part is pretty self explanatory, especially if you purchased a lithium battery like I did. You will want to install the battery on a piece of foam so you don’t break the lithium cells. I took packaging foam and placed it between the battery and the frame. I also used Velcro straps to attach the battery. This way I could remove the battery if needed.

Throttle

I ended up buying  a throttle with a three speed button and voltage reader. This was super easy to install and you just slide them on the bars. If you are having trouble sliding them on try using a little bit of gasoline on the bars to slide them on. This way the gas will evaporate and leave them stuck on. If you use water or a lube they will turn on the bars and it won’t be safe. The voltage meter is super helpful because you fan figure out how much battery you’ve used! Mine reads 54.4 volts when fully charged. Even thought it is a 48v battery. According to the sticker on the battery it is fully dead at 30v. We haven’t gotten ours down past 46 volts yet! That was after 20 miles of riding (with a 7 year old driving it)

Wiring and Controller

I used a junction box to do most of the wiring, this way I could take everything apart if needed. I try to do too much hard wiring so I can service everything easier. Most wires are color coordinated and labeled from the controller. The only thing to really note here is if you don’t have an ignition key or switch you will need to connect the two wires labeled “E Lock” or “Electronic Lock”. It will not work even with the the main switch. You will need to connect these two wires to each other. If you are using an aftermarket key or ignition switch then you can attach these two wires to that.

Final Wiring

The most common mistake people make the final switch wiring. See my photos below to see how to wire that. If you installed a throttle with a three position switch you will notice the wiring colors will not line up. See photos below to see how to wire that.

Tips

Most of the connects did not match when doing my install. The throttle connectors, three position wires and the Electronic Lock connecters did not match up. The easiest way to connect these without cutting the wires is to crush the plastic connector on the male side. Use plyers to crush the connector. You will still have the metal sawdered connector on the endo the wire and you can easily stick those into the female side. They make a great connection and you can run electrical tape on the outside of that if you want to secure it even more.

Final Stats

• Top speed increased to just over 30MPH with stock gearing
• Torque is insane and it will wheelie like crazy
• Range has increased to over 20 miles! (with my son on it). We haven’t run out of battery yet and we have done several rides over 20 miles in one rip. Pretty insane!

If you can pick one of these bikes up for cheap then jump on it! I bought mine without a motor or batteries for under 100 dollars. This is the third upgrade I’ve done on the bike and by far the best upgrade I’ve done is the battery.