My baja 5E....sort of

[Revracer]

i looked at this KB45 and really like it. it makes massive power. it be great for my terra crusher build im about to do. itll be my least expensive build ever! but those motors can make nearly 4k watts... which is friggin huge... great for my 12lbs crusher... but they have a 6mm shaft... i dont wanna try to shave the shaft down so how could i fit a pinion onto that?