- Fri Dec 30, 2011 4:23 am
Just a Noob's two cents: It's really all about the age old conundrum which answers one question with yet another question, "How fast do you want to go? How much money do you want to spend?" My son and I JUST finished modding his stock 300. This was the first time he or I had attempted any such mods. I'd read this post to gather some 'lessons learned' but go to the pros for the expert advice.
Out of the box speed on a 300 is between 12 and 15 mph, uses a 24volt motor/controller/throttle and charger system. We took his to 48 volts, (4x12v/9aH batteries) a 48 volt controller, a 48 volt charger, 48 volt 5 pin throttle with led charge indicators and a 36 volt, 500 watt motor. Speed confirmed only by hand-held GPS is now 24 MPH for him (92 lbs.) and 19 mph (195 lbs.) for me.
Lessons learned: simply adding a 3rd battery is BY FAR the cheapest/easiest route but will not get you to 25 mph. Be sure to buy batteries that are the same PHYSICAL size as the stock 12v 7aH batteries. The best I could find with the exact same physical dimensions were 12 v 9aH. The increase in amp-hours does not translate to longer ride-time because the only reason you're doing any of this in the first place is to make the scooter faster. Going faster = quicker use of any aH gain.
Don't buy batteries online. Go to your local "Batteries Plus" or similar. They were cheaper and removed guess work regarding dimensions. To make room for all 4 batteries we had to stand 3 of them upright, as opposed to laying them down on their sides inside the pan (stock method) and create a metal riser that sets on top of the stock metal frame and lifts the deck about an inch higher than it used to be. Obviously, this means you have to buy new/longer (nuts, bolts, etc...) This is a bigger pain than one would think. All Razor hardware is metric and obtaining the correct size, thread tap, head bezel, length, etc... was difficult.
There are all sorts of methods out there for securing the 4th battery. I chose to fabricate a small metal box that bolts directly to the deck and right on top of the rear wheel well hump. I had to add some extra metal pieces for support. The stock frame/deck are not strong enough to adequately hold the 4th battery.
The new motor had a larger diameter than the stock by about half an inch. We got around this by buying the knobbied "off road" tires vs. the stock "slick" tires. This was a mistake. More research on my behalf would have led me to dozens of motors with similar power and output without the increase in diameter and length. Oh yeah, there's another hitch: whichever motor you choose, keep the dimensions as close as possible to the stock motor ( I swear this is possible and would have saved a ton of head-ache ). We had to saw off the stock kick-stand and it's mount so the motor and rear sprocket would align. We also had to re-route the brake cable. Additionally, the 36v 500 watt motor was probably not the best choice for top-end speed either. It added a TON of low end torque (a grown man can easily pop the front wheel off the ground by slamming the throttle all the way back) but if top-speed is your goal and I had it all to do over again, I'd go with a brush less.
The bottom line is that I spent far more money than required, did/re-did many things repeatedly but learned a lot and had a great time with my son. The scooter runs and charges perfectly. He gets about 3 hours of max-speed ride-time with no significant fall off in power until about 3 1/2 hours. The new electronics are flawless thus-far. I sealed up holes and gaps created by the new deck lifting frame with black caulk, made sure all the internals were water tight by using heat-shrink, crimp-on connectors jacketed in rubber, rubber grommets, electrical tape and even some hot glue. In the end, it was expensive, sometimes frustrating, did I mention expensive? But I can say without hesitation: I'd do it again. The scooter is a total blast to ride and it's fun watching the other kids with their stock scooters get smoked ( internally fun, of course).