How do I change my one-piece cranks to three-piece cranks on my BMX bike?

I have a Diamondback Viper with a large bottom bracket, a one-piece 165mm crank and a 45 tooth sprocket. I would like to change it to a lighter, smaller sprocket. What do I have to change? Also, what is an ISIS bottom bracket??? Should I keep the same length cranks and same tooth sparocket? I'm guessing I will need to switch chains as well. Please help, Thanks!!!How do I change my one-piece cranks to three-piece cranks on my BMX bike?If you want to go from 1 to 3 peice cranks...first you need to take the bearings and cups out of your frame(cups-what the bearings are in). Then you need to get yourself a new set of bearings that will fit in your bottom bracket(yours are prob american).Your sprocket will not work with a 3 peice cranks unless you get an hat adapter to go on the inside of your sprocket. An isis bb is another name for a euro bb I think...either way you need American bb bearings. If you go from a big sprocket to a small one you can cut the chain down to the right linkege that you need. Hope this helps you out bro! Have fun



-Sam