Razor MX650 mini bike build

hitting a sweet jump

Been riding this thing into the ground for a few years now. Picked up a brand new one and figured it was time to make the older one more adult friendly. Goal is enough torque to be able to climb some decent dirt trails and still have 5+ mile range.

First mod - added a beer holder

Second - changed out the motor sprocket from 11t to 9t.

Third - swapped out the rear shock for a 200mm pitbike shock and raised the rear up a few inches.

Forth - Went to 48v

Fifth - will be to pick up a 48v 1800w brushless setup whenever ebay has another 15-20% off coupon

Six - if the torque still sucks will be to get a rebel gears 96T or 100T rear sprocket.


On the maybe list:
Handlebars
crf50 tall seat
wider rear tire

Shock difference


Batteries mounted and wired with 10ga.
Soldered the charging plug directly to the battery. Bought a cheap 48v charger and going to cut the end off and solder on the original plug. And what the motor shaft bearings looks like.
Ordered an lcd volt gauge as well to hopefully keep me from over discharging the batteries. At least until I get a 48v controller


The mx has been getting slower and only lasting a mile or two vs the 10 miles they are supposed to last. So after replacing the batteries and checking the batteries multiple times I took the motor apart. And the bearing the shaft rides in was completly rusted. So cleaned up the motor with a scuff pad and starting fluid and order new bearings.



Took off the dust shields on the new bearing and packed with quality high temp grease. (seems to make these cheap Chinese bearings last longer)

Got the motor mounted and realized the chain had a tweaked link in it, so made a new chain with some spare I had.

Cut the side plastics to fit the forth battery. Then the yellow fenders cover the battery so it is out of site.

Power still leaves a lot to be desired so will be getting the Chinese 1800w motor setup next for her.

Picture is of a 100% stock one and the one I just finished. You can see the height difference by comparing the rear fender height off the back tire.

Looks fun. Did you go 48v straight to the stock controller?

Didn't see a picture of your beer holder btw....

Correct! 48v to stock 36v controller. Plus running the smaller motor sprocket means she ain't working as hard so should not be an issue. Or at least last me until I upgrade. I will grab a pic of the beer holder in use next ride.

Have you put the 1800w kit on yet? I am interested to know the speed difference. I’ve got an mx650, two mx350s, and I just ordered an mx125. I was thinking about putting the 48v 1800w kit on the mx650 and dropping the the old kit in one of the mx350s, then dropping the 350 into the mx125. I plan on starting a thread on that whole process.

What is your take on a 72v 3000w in a mx650?? Is it worth it to go with that or just run a 48 1800w?

Kpackresto said:

What is your take on a 72v 3000w in a mx650?? Is it worth it to go with that or just run a 48 1800w?

Click to expand...

The 48v 2000w with kelly controller is pretty damn fast.

Here is mine. Currently running 48v 1800w brushless setup with front 10t sprocket and rear 89T. Battery is 48v 18ah li-ion

https://www.youtube.com/watch?v=SNfqoECroak

Which brushless motor is that?

Sent from my LM-G850 using Tapatalk

oded said:

Which brushless motor is that?

Sent from my LM-G850 using Tapatalk

Click to expand...

Boma 48v 1800w kit. Get them on amazon for 100-120ish. I would recommend buying the 48v 2000w kit.

these motors produce enough torque? heard they are built for RPM, not torque.

I put the 72v 3000w kit on a mega moto mini bike and put its 36v 1000w motor and controller on a mx350. They all have about the same stall torque but the 72v version goes to a much higher rpm. Off the line the bikes were about the same, the 72v mini bike just kept going upto about 45mph. The other problem with the 72v kit is its a bit harder to source the 72v battery and fit to the frame. But if total speed is what you are looking for the 72v provides plenty for that little frame. I haven't had any problems to date(2 years) with the kit.

those mx650's have a bunch of potential how much space is there where the stock motors mount might have to lower a mid motor to fit under the shock mount bar or put it above the wheel with a higher cog

I believe all of those kunray style motors are the same size, they should all fit in the same spot, it's really just about the battery and controller mounting. Can be done fairly easily. A couple YouTube videos already out there on it.

I think the mega moto frames are better but if you can get a cheap mx650 that would be sweet.

https://youtu.be/gEqyTZ08i4A

If you run a kelly controller and feed them the amps they will make a ton of torque. Buddy has the 48v 2000w motor with crap ebay battery and kelly controller. Bike will throw you off if your not careful. How long these crap motors will last using those kinds of amps is the question. Could always go with a qs-90 motor too.

Rather then continuing to dump money into the mx's I got a Sur-ron. And holy moly these things are awesome!
https://www.youtube.com/watch?v=ivG-yOOF-Og&t=108s