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Discussion Starter · #1 ·
Hello all. I have been reading this forum and a couple of others trying to get some answers on a couple of specific questions. My apologies if I have missed the threads that would have answered. We are looking at an MX500 for my daughter. We wanted the MX650, but none used close to us. I'm looking at ways to get a few more MPH top speed out of it, nothing crazy. Since everything I read says they are basically the same bike except for the motors, can't you simply put a 650 motor in the 500? If not, why? The other question is more of someone's personal experience. For the under 100# weight, would going to a 14 tooth front sprocket, or a 55 tooth rear sprocket, or a 13 front and 65 rear, bog it down too much at launch? The bike will be ridden on a flat paved road 99.99% of the time. Thanks in advance!!
 

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What's your poison? Mine is 40:1
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Welcome, yes the 650 is a direct bolt in. So is the 36v 800w motor. In my experience, the mx500 with 185lb rider is 16, the 650 is 17.5-18mph. With an 80lb rider 18 and 20 respectively. Now going from the 500 to 800, should net another 1.5-2 mph over the 650. I personally have never changed sprockets yet. But general rule, bigger front and/or smaller rear more top end, smaller front bigger rear more torque or low end.
First mod, lithium battery, whether you build a pack or buy one. Highly recommend. Then the 36v 800w motor.
After that, you could do the Raddads controller mod, then run 48v battery, but you should decide before you buy the battery considering the expense.
But just the mod, 800w motor and lithium, with stock sprockets, i would guess 20-21 w/185lb rider and 22-23 w/80lb rider. Every motor is different so could be + or - but would be close. Overvolting is great but you have to be cautious for motor heat and battery size.
 

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Discussion Starter · #3 ·
Thanks, but no serious mods here, we'll go gas first. We did all that with the Power Wheels thru the years. A lot of expense with little return. I'll check out the 800W motor, I'm thinking a little bigger motor for some torque then gear it up some.
 

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I hear you, if you guys don't mind 30-minute rides or Less and an 8-hour charge or so on the lead acid batteries then yes motor swap and sprocket changes. I usually buy my sprockets from electricscooterparts.com
 

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Discussion Starter · #5 ·
Yep, that's fine. When the batteries go bad we'll review. She's 12 now, so this could easily all go by the wayside within the year. That's why if she starts getting bored (little speed freak) for $100 I could get her a few more MPH. That's why I was asking about real world experience on the slight motor upgrade and the higher gearing, I don't want it to be a dog off the line.
 

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I hear you. That would be a good start. Nothing wrong with some slow upgrades
 

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Discussion Starter · #7 ·
OK, just did some calculating using some online calculators. I get these are theoretical estimates without baking in a lot of factors, but directionally it makes sense, so...

Stock set up, 15.4 MPH (2500 RPM)
Overvolting stock set up, 20.3MPH (3300 RPM) $30 Some risk
Adding 800W with new controller at 36V, 17 MPH (2750 RPM) $230
Adding 800W with new controller at 48V, 22.5 MPH (3600 RPM), $260

Easily the best bang for the buck is just adding another SLA.

Buuuut, with the full conversion pretty sure I could go with a 13 tooth motor sprocket without losing appreciable low end over the stock set up, if any at all.
It would get me to 26.7 MPH for an additional $10, or $270 total.
Add a 68 tooth rear, 30.8 MPH for $290 total.
 

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Ha, real world is definitely different. My buddies is an Mx500, swapped 24v 500w motor, 36v 1000w controller and a 36v 10ah lithium battery pack, stock sprockets. 27mph max with 200lbs on it. But typically 25-26mph. Have not tested with an 80lb kid. Someday. Lol. 25mph is easy. With you kid, 800w motor ALONE should net between 20 and 22mph. I might test this......
 

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Just remember, watts is torque, rpm is top speed. Overvolted nets roughly 50% more watts and rpm. 500 now 750, 2500 rpm now 3700rpm, but comes with heat.
 

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Razor mx500 (mildly modded monster)
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From my experience the best bang for your buck is to scoop a 4th 12v sla battery, grab a 48v sla battery charger from Amazon or somewhere and modify your speed controller as I do (have a thread about it and it's free minus some solder and a piece of wire or metal). I did exactly that to an sx500 for a neighbor with a 9 year old boy and his bike topped out around 25mph and launched far better than stock... plus being a lightweight rider the motor didn't get overly hot.
 

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The mod I do on every stock speed controller and it works beautifully.
 

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I agree just add a battery to your already good SLA bank and mod the speed control by the time the SLA bank dies you should have more money saved up to get quality components and parts.
 

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Going with the 800w 36v motor for now. If we overvolt, I'll get a bigger controller.
Don't expect to see much performance gains from just the motor alone amigo, it's still gonna be seeing the same amount of juice the 500w did.
 

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Discussion Starter · #15 ·
I get a 2 MPH gain with an option to overvolt. Much more is just stupid, the same money buys a Honda or Yamaha.
 

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I get a 2 MPH gain with an option to overvolt. Much more is just stupid, the same money buys a Honda or Yamaha.
Maybe a China pit bike but then it whouldent be electric.

Over volting a 36v motor does give you the most bang for your buck.
 

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Especially with another 12v 12ah sealed lead acid battery and a 48v sla battery charger from Amazon or somewhere costing like $50 total.
 

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All he wanted at this point for his kid was a few mph and more low end takeoff. WITH the option to continue the mods.
The stock 36v 500w motor only has 2500 rpm, the 650 motor 2750 rpms, (most) 800w 2800.
MAKE SURE you find the highest rpm 800w motor. I have seen 2750-2850.
Rpm is top speed and watts is takeoff power.
 

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Especially with another 12v 12ah sealed lead acid battery and a 48v sla battery charger from Amazon or somewhere costing like $50 total.
Without me going back into threads.......
What is the controller mod worth in top speed by itself???
 

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Discussion Starter · #20 ·
All he wanted at this point for his kid was a few mph and more low end takeoff. WITH the option to continue the mods.
The stock 36v 500w motor only has 2500 rpm, the 650 motor 2750 rpms, (most) 800w 2800.
MAKE SURE you find the highest rpm 800w motor. I have seen 2750-2850.
Rpm is top speed and watts is takeoff power.
You nailed it. We have already done the electric ride ons and doing all the speed tricks, so I got the hobby side out of my system, now it's just so the kid can have some fun. I got the 2750 RPM, which alone gets me 2-3 MPH. If I eventually overvolt and run a 48V controller, I can get it to about 3500 RPM, or around 23mph. Add a bigger motor sprocket, which I think the new motor will handle just fine and why I went 800W rather than the 650W (2800RPM), I can get about 25MPH. For now we'll add on until we hit the woohoo speed and then stop.
 
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