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Moderators: robnewyork, bassiclyLouDog, gameboy

By summbear48
Picked up 3 Mx's for $100. They were all shot to hell and back but already had lots of extra parts from other builds. Replaced odds and ends, planning on 14s Lipo battery, so was also thinking of running my yk43b controller. The motor was in bad shape already so knew it was going out. To not kill another motor I will probably re gear the back sprocket. Don't really need it to go over 20 mph. More interested in darting around in the dirt. But do any of you have any motor combination suggestions for the yk43b? Drop ins would be easiest but not afraid to weld up a bit. Or maybe you have one for sale?
What I have done:
Yk43b controller
Need motor
14s 10ah battery build with BMs
80v LED
Led throttle with light switch
Battery disconnect
New xr50 plastics and graphics kit
Extended shock
Taller foam seat
New tires and derusted rims via electrolysis
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By robnewyork
nice resto! i only have a giant industrial, good news is 800w 36v are 69.99 shipped on ebayy
By robnewyork
nice resto! i only have a giant industrial, good news is 800w 36v are 69.99 shipped on ebayy
By summbear48
I have found 9t for the front and 89 for the back. I dont really want tons of speed on this guy, should I do one? (front or back?) or just hit both? looks like if I got the 800w motor, it would overvolt to 4500 rpms and with 12.5 inch tires, top speed of 16 mph with both sprockets or around 20 with 1. just dont want to mash the motor too hard with the yk43b...thoughts?
By robnewyork
thats a shopping cart link, i cannot see anything//
as far as the gearing math, its wrong since youre only overvolting 1/3rd. not 1/2.. so at 48v the 36v 800 is running 3700 rpm , not 4500.

why not just run the stock gearing, 11-80 and have a good 14 mph ( whatever the stock top speed is ) .. get the junior yk43b which is 55amps , not 196amps then no worries about frying the motor
By robnewyork
if its for dirt, and u want insane torque and not a lot of top speed.. do the 89 tooth rear, keep the 11 front , run the real YK43b , and run it at 36v.. this will give a hair under stock top speed.. maybe 12-13.. test that , test motor temp , then add the 4 th battery for 18-20mph
By summbear48
I do have the real yk43b, so that is what I was planning.
I was doing my calculations with the 800w motor. 2800rpm divided by volts (36) = 77.7 rpm/volt. so if I put it at 58v (14s lipo batt I have) it should run at about 4500 rpms, no?. Though I am not interested in top speed, 20mph give or take would be fine. definitely want a little torquey ride. I extended front forks and will include a picture. needed to be a bit taller after back shock replacement.
the 650 motor I have is really bad, I took it apart and did a good cleaning but it just doesnt perform on my 12s lipo. it doesnt feel any better than my sons mx500 with an extra 12v battery in it, stock controller. So something is up.
the link I attached (sorry) was an imperial... but he is listing them all over and the other link he was charging less than half of the shipping cost he is here on ebay...
also this one...
but plug and play the 800w seems less stress. I just want to start riding with my boys :)
By robnewyork
320 rpm, too low,.. yea, 800w easier.. yes, at 58v , 4500 rpm.. my issue is, will the 800 handle yk43b at 58v? who start with stock gears and 36v yk43b, and have the additional batteries ready to add after checking heat

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