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40MPH MX 650 75v Lipo 48v cont 90T sprocket

7K views 4 replies 3 participants last post by  bbrf033 
#1 ·
Lots of people ask how to get a MX500 and MX650 to perform better.

So i have been doing a lot of experimenting with my "Sons" Razor MX650. It is a fun platform but lame in stock form. Out of the box it did about 17 with little torque.We have looked over the forums and have seen some others go up to 60v with SLA's but that is just way too heavy in the wrong place on the bike. People have also cut the swingarm to put in bigger 48v and 60v motors.

I have since replaced the SLA's with 6 x 6S 5800 Turnigy lipos in a 18S 2P configuration for a solid 75v and an hour or so of run time. We are into RC racing so have equipment to charge the packs and understand the safety issues with Lipo. We have been trying different motors. The largest that will fit stock is a 36v 750 watt although you have to swap end plates on the motors to get it to fit. We put in a 48v 50amp controller from TNC to eliminate some of the shunting in the stock controller.

The next big challenge was the gearing. way too high to get offroad dirt bike performance. We tried the 90t currie sproket but that was a piece of _ _ _ _.
I then found Rebel Gears. WOW - they make the most awesome sprockets out of 7076 T6 aluminum for drag bikes. They built me 90t and 100T #25 sprockets. 45 dollars plus shipping 3 day turnaround.

With 90T rear 11tooth front and 75v the bike does 40mph with my 80lb son!!!! With the 100T its at about 32Mph and it will pull a wheelie. Now we need better tires!

Now we need Gary's (from endless-sphere forum) 4.0 BMS. We fried one of the batteries yesterday because of no LVC! we had been monitoring one of the packs manually and got lazy so we will now wait until we have it before throwing another $100 in the trash.
 
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#3 ·
6x6S 5800mah lipos =75v at 10600mah. lasts forever like over an hour of hard riding.
6 x $89 =$540.
48v cont =30
Rebel Gears 100T sprocket = 50.
More aggressive knobby's for front and rear =80
Enduro Headlight =40
i also have LVC cuttof boards 3 at 40 a piece.
and 3 6S balancers on board at 20 a piece
75v charger from Ping Battery = $60
 
#5 ·
fantastic info. I want to get a 90t sprocket from rebel gears but I need help.
the drop down info for things like inner diameter, bolt circle and other stuff. if you have this info and can pass it on, I'd appreciate it. also. the drop downs for number of teeth stop at 76. do I just put 90 teeth in the comments? thx
 
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