The crank wont be balanced unless you buy a kit with all the pieces together. If you buy the crank separately, whoever you buy it from wont know what rods and piston and stuff you will be using to be able to balance it. And that puts all the burden on you to provide all that info to the person that will balance it. If you transpose a number or if they do you can have a big problem, and that has happened. Plus when you buy a kit you usually get a package deal as opposed to buying the parts individually.
